diff --git a/.github/workflows/check_lesson_25_java_pr.yaml b/.github/workflows/check_lesson_25_java_pr.yaml
new file mode 100644
index 000000000..8103d49f2
--- /dev/null
+++ b/.github/workflows/check_lesson_25_java_pr.yaml
@@ -0,0 +1,28 @@
+name: Check Lesson 25 Java Pull Request
+
+on:
+  pull_request:
+    branches: [ "main" ]
+    paths:
+      - "lesson_25/db/**"
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      pull-requests: write
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - name: Set up JDK
+      uses: actions/setup-java@v4
+      with:
+        java-version: '21'
+        distribution: 'temurin'
+
+    - name: Build Lesson 26 with Java
+      working-directory: ./lesson_25/db
+      run: ./gradlew check
\ No newline at end of file
diff --git a/lesson_25/README.md b/lesson_25/README.md
index 8099277b7..cb2131689 100644
--- a/lesson_25/README.md
+++ b/lesson_25/README.md
@@ -13,4 +13,27 @@ Please review the following resources before lecture:
 
 ## Homework
 
-- TODO(anthonydmays): Add more information.
\ No newline at end of file
+- [ ] Complete [Loading the Library, Part II](#loading-the-library-part-ii) assignment.
+
+
+### Loading The Library, Part II
+
+Instead of loading our library data from JSON or CSV files as we did in [lesson_10](/lesson_10/), we now want to load data from a proper database. A new implementation of the `LibraryDbDataLoader` data loader has been provided to accomplish this task and is now the [default data loader][library-app] for the app.
+
+To build familiarity in working with databases, you are charged with the following tasks:
+
+* Write a `.sql` script file that queries the following data. Use a unique name for your file and store it in the [queries][queries-dir] directory of the resources folder.
+    * A `SELECT` query that returns the counts of media items by type.
+    * A `SELECT` query that returns the sum of total pages checked out by guests.
+    * A `SELECT` query that shows all 5 guests and any corresponding records in the `checked_out_items` table.
+* Add a new table called `library_users` to the [SQLite database][sqlite-db] that stores a user's id (UUID formatted string), email, first name, last name, and a password (bcrypt encoded string). Add a model and repository that loads the users into the LibraryDataModel (see `LibraryGuestModel` and `LibraryGuestRepository` as examples). Populate the database with a few users.
+
+As before, you can run the app from the console using the following command:
+
+```bash
+./gradlew run --console=plain
+```
+
+[queries-dir]: ./db/db_app/src/main/resources/queries/
+[sqlite-db]: ./db/db_app/src/main/resources/sqlite/
+[library-app]: ./db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryApp.java#L26
diff --git a/lesson_25/createdb/createdb.py b/lesson_25/createdb/createdb.py
new file mode 100644
index 000000000..a8af9b776
--- /dev/null
+++ b/lesson_25/createdb/createdb.py
@@ -0,0 +1,23 @@
+import os
+import pandas as pd
+import numpy as np
+import sqlite3
+
+# Step 1: Load the CSV file into a pandas DataFrame
+media_items_df = pd.read_csv('/workspaces/code-society-25-2/lesson_12/io/io_app/src/main/resources/csv/media_items.csv')
+guests_df = pd.read_csv('/workspaces/code-society-25-2/lesson_12/io/io_app/src/main/resources/csv/guests.csv')
+checked_out_items_df = pd.read_csv('/workspaces/code-society-25-2/lesson_12/io/io_app/src/main/resources/csv/checked_out_items.csv')
+checked_out_items_df['due_date'] = pd.to_datetime(checked_out_items_df['due_date']).values.astype(np.int64)
+
+# Step 2: Create a connection to the SQLite database
+# Note: This will create the database file if it doesn't exist already
+os.makedirs('/workspaces/code-society-25-2/lesson_25/db/db_app/src/main/resources/sqlite/', exist_ok=True)
+conn = sqlite3.connect('../db/db_app/src/main/resources/sqlite/data.db')
+
+# Step 3: Write the DataFrame to the SQLite database
+media_items_df.to_sql('media_items', conn, if_exists='replace', index=False)
+guests_df.to_sql('guests', conn, if_exists='replace', index=False)
+checked_out_items_df.to_sql('checked_out_items', conn, if_exists='replace', index=False)
+
+# Don't forget to close the connection
+conn.close()
\ No newline at end of file
diff --git a/lesson_25/createdb/requirements.txt b/lesson_25/createdb/requirements.txt
new file mode 100644
index 000000000..1411a4a0b
--- /dev/null
+++ b/lesson_25/createdb/requirements.txt
@@ -0,0 +1 @@
+pandas
\ No newline at end of file
diff --git a/lesson_25/db/.gitattributes b/lesson_25/db/.gitattributes
new file mode 100644
index 000000000..097f9f98d
--- /dev/null
+++ b/lesson_25/db/.gitattributes
@@ -0,0 +1,9 @@
+#
+# https://help.github.com/articles/dealing-with-line-endings/
+#
+# Linux start script should use lf
+/gradlew        text eol=lf
+
+# These are Windows script files and should use crlf
+*.bat           text eol=crlf
+
diff --git a/lesson_25/db/.gitignore b/lesson_25/db/.gitignore
new file mode 100644
index 000000000..1b6985c00
--- /dev/null
+++ b/lesson_25/db/.gitignore
@@ -0,0 +1,5 @@
+# Ignore Gradle project-specific cache directory
+.gradle
+
+# Ignore Gradle build output directory
+build
diff --git a/lesson_25/db/db_app/build.gradle.kts b/lesson_25/db/db_app/build.gradle.kts
new file mode 100644
index 000000000..88c3a8b1d
--- /dev/null
+++ b/lesson_25/db/db_app/build.gradle.kts
@@ -0,0 +1,79 @@
+plugins {
+    // Apply the application plugin to add support for building a CLI application in Java.
+    application
+    eclipse
+    id("com.diffplug.spotless") version "6.25.0"
+	  id("org.springframework.boot") version "3.4.0"
+    id("com.adarshr.test-logger") version "4.0.0"
+}
+
+apply(plugin = "io.spring.dependency-management")
+
+repositories {
+    // Use Maven Central for resolving dependencies.
+    mavenCentral()
+}
+
+dependencies {
+    // Use JUnit Jupiter for testing.
+    testImplementation("com.codedifferently.instructional:instructional-lib")
+    testImplementation("org.junit.jupiter:junit-jupiter:5.11.3")
+    testImplementation("org.springframework.boot:spring-boot-starter-test")
+    testImplementation("org.assertj:assertj-core:3.26.3")
+    testImplementation("at.favre.lib:bcrypt:0.10.2")
+    testCompileOnly("org.projectlombok:lombok:1.18.38")
+    testAnnotationProcessor("org.projectlombok:lombok:1.18.38") 
+
+    // This dependency is used by the application.
+    implementation("com.codedifferently.instructional:instructional-lib")
+    implementation("com.google.guava:guava:33.3.1-jre")
+    implementation("com.google.code.gson:gson:2.11.0")
+    implementation("commons-cli:commons-cli:1.6.0")
+    implementation("org.springframework.boot:spring-boot-starter")
+    implementation("org.springframework.boot:spring-boot-starter-data-jpa")
+    implementation("com.fasterxml.jackson.core:jackson-databind:2.13.0")
+    implementation("com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.12.3")
+    implementation("com.opencsv:opencsv:5.9")
+    implementation("org.apache.commons:commons-csv:1.10.0")
+    implementation("org.xerial:sqlite-jdbc:3.36.0")
+    implementation("org.hibernate.orm:hibernate-community-dialects:6.2.7.Final") 
+    compileOnly("org.projectlombok:lombok:1.18.38")
+    annotationProcessor("org.projectlombok:lombok:1.18.38")
+}
+
+application {
+    // Define the main class for the application.
+    mainClass.set("com.codedifferently.lesson25.Lesson25")
+}
+
+tasks.named<JavaExec>("run") {
+    standardInput = System.`in`
+}
+
+tasks.named<Test>("test") {
+    // Use JUnit Platform for unit tests.
+    useJUnitPlatform()
+}
+
+
+configure<com.diffplug.gradle.spotless.SpotlessExtension> {
+
+  format("misc", {
+    // define the files to apply `misc` to
+    target("*.gradle", ".gitattributes", ".gitignore")
+
+    // define the steps to apply to those files
+    trimTrailingWhitespace()
+    indentWithTabs() // or spaces. Takes an integer argument if you don't like 4
+    endWithNewline()
+  })
+
+  java {
+    // don't need to set target, it is inferred from java
+
+    // apply a specific flavor of google-java-format
+    googleJavaFormat()
+    // fix formatting of type annotations
+    formatAnnotations()
+  }
+}
diff --git a/lesson_25/db/db_app/lombok.config b/lesson_25/db/db_app/lombok.config
new file mode 100644
index 000000000..6aa51d71e
--- /dev/null
+++ b/lesson_25/db/db_app/lombok.config
@@ -0,0 +1,2 @@
+# This file is generated by the 'io.freefair.lombok' Gradle plugin
+config.stopBubbling = true
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/Lesson25.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/Lesson25.java
new file mode 100644
index 000000000..9de75af9f
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/Lesson25.java
@@ -0,0 +1,39 @@
+package com.codedifferently.lesson25;
+
+import com.codedifferently.lesson25.cli.LibraryApp;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.CommandLineRunner;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.context.annotation.Configuration;
+
+@Configuration
+@SpringBootApplication(scanBasePackages = "com.codedifferently")
+public class Lesson25 implements CommandLineRunner {
+
+  @Autowired private LibraryApp libraryApp;
+
+  public static void main(String[] args) {
+    var application = new SpringApplication(Lesson25.class);
+    application.run(args);
+  }
+
+  @Override
+  public void run(String... args) throws Exception {
+    // Don't run as an app if we're running as a JUnit test.
+    if (isJUnitTest()) {
+      return;
+    }
+
+    libraryApp.run(args);
+  }
+
+  private static boolean isJUnitTest() {
+    for (StackTraceElement element : Thread.currentThread().getStackTrace()) {
+      if (element.getClassName().startsWith("org.junit.")) {
+        return true;
+      }
+    }
+    return false;
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryApp.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryApp.java
new file mode 100644
index 000000000..44053bd61
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryApp.java
@@ -0,0 +1,196 @@
+package com.codedifferently.lesson25.cli;
+
+import com.codedifferently.lesson25.factory.LibraryDataLoader;
+import com.codedifferently.lesson25.factory.LibraryDbDataLoader;
+import com.codedifferently.lesson25.factory.LibraryFactory;
+import com.codedifferently.lesson25.library.Book;
+import com.codedifferently.lesson25.library.Library;
+import com.codedifferently.lesson25.library.LibraryInfo;
+import com.codedifferently.lesson25.library.MediaItem;
+import com.codedifferently.lesson25.library.search.SearchCriteria;
+import java.util.Map;
+import java.util.Scanner;
+import java.util.Set;
+import org.apache.commons.cli.CommandLine;
+import org.apache.commons.cli.CommandLineParser;
+import org.apache.commons.cli.DefaultParser;
+import org.apache.commons.cli.HelpFormatter;
+import org.apache.commons.cli.Option;
+import org.apache.commons.cli.Options;
+import org.apache.commons.cli.ParseException;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+@Service
+public final class LibraryApp {
+
+  @Autowired private LibraryDbDataLoader defaultLibraryDataLoader;
+
+  public void run(String[] args) throws Exception {
+    // Load the library using the specified loader from the command line or the default.
+    LibraryDataLoader loader = getLoaderOrDefault(args, defaultLibraryDataLoader);
+    Library library = LibraryFactory.createWithLoader(loader);
+
+    // Show stats about the loaded library to the user.
+    printLibraryInfo(library);
+
+    try (var scanner = new Scanner(System.in)) {
+      LibraryCommand command;
+      // Main application loop.
+      while ((command = promptForCommand(scanner)) != LibraryCommand.EXIT) {
+        switch (command) {
+          case SEARCH -> doSearch(scanner, library);
+          default -> System.out.println("\nNot ready yet, coming soon!");
+        }
+      }
+    }
+  }
+
+  private void printLibraryInfo(Library library) {
+    LibraryInfo info = library.getInfo();
+    Map<String, Set<MediaItem>> checkedOutItemsByGuest = info.getCheckedOutItemsByGuest();
+    int numCheckedOutItems = checkedOutItemsByGuest.values().stream().mapToInt(Set::size).sum();
+    System.out.println();
+    System.out.println("========================================");
+    System.out.println("Library id: " + library.getId());
+    System.out.println("Number of items: " + info.getItems().size());
+    System.out.println("Number of guests: " + info.getGuests().size());
+    System.out.println("Number of checked out items: " + numCheckedOutItems);
+    System.out.println("========================================");
+    System.out.println();
+  }
+
+  private static LibraryDataLoader getLoaderOrDefault(
+      String[] args, LibraryDataLoader defaultLoader) throws Exception {
+    String loaderType = getLoaderFromCommandLine(args);
+    return loaderType == null
+        ? defaultLoader
+        : Class.forName(loaderType)
+            .asSubclass(LibraryDataLoader.class)
+            .getDeclaredConstructor()
+            .newInstance();
+  }
+
+  private static String getLoaderFromCommandLine(String[] args) throws IllegalArgumentException {
+    Options options = new Options();
+    Option input = new Option("l", "loader", true, "data loader type");
+    input.setRequired(false);
+    options.addOption(input);
+    CommandLineParser parser = new DefaultParser();
+    HelpFormatter formatter = new HelpFormatter();
+    try {
+      CommandLine cmd = parser.parse(options, args);
+      return cmd.getOptionValue("loader");
+    } catch (ParseException e) {
+      System.out.println();
+      System.out.println(e.getMessage());
+      formatter.printHelp("utility-name", options);
+
+      System.exit(1);
+    }
+    return null;
+  }
+
+  private static LibraryCommand promptForCommand(Scanner scanner) {
+    var command = LibraryCommand.UNKNOWN;
+    while (command == LibraryCommand.UNKNOWN) {
+      printMenu();
+      var input = scanner.nextLine();
+      try {
+        command = LibraryCommand.fromValue(Integer.parseInt(input.trim()));
+      } catch (IllegalArgumentException e) {
+        System.out.println("Invalid command: " + input);
+      }
+    }
+    return command;
+  }
+
+  private static void printMenu() {
+    System.out.println("\nEnter the number of the desired command:");
+    System.out.println("1) << EXIT");
+    System.out.println("2) SEARCH");
+    System.out.println("3) CHECKOUT");
+    System.out.println("4) RETURN");
+    System.out.print("command> ");
+  }
+
+  private void doSearch(Scanner scanner, Library library) {
+    LibrarySearchCommand command = promptForSearchCommand(scanner);
+    if (command == LibrarySearchCommand.RETURN) {
+      return;
+    }
+    SearchCriteria criteria = getSearchCriteria(scanner, command);
+    Set<MediaItem> results = library.search(criteria);
+    printSearchResults(results);
+  }
+
+  private LibrarySearchCommand promptForSearchCommand(Scanner scanner) {
+    var command = LibrarySearchCommand.UNKNOWN;
+    while (command == LibrarySearchCommand.UNKNOWN) {
+      printSearchMenu();
+      var input = scanner.nextLine();
+      try {
+        command = LibrarySearchCommand.fromValue(Integer.parseInt(input.trim()));
+      } catch (IllegalArgumentException e) {
+        System.out.println("Invalid command: " + input);
+      }
+    }
+    return command;
+  }
+
+  private void printSearchMenu() {
+    System.out.println("\nEnter the number of the desired search criteria:");
+    System.out.println("1) << RETURN");
+    System.out.println("2) TITLE");
+    System.out.println("3) AUTHOR");
+    System.out.println("4) TYPE");
+    System.out.print("search> ");
+  }
+
+  private SearchCriteria getSearchCriteria(Scanner scanner, LibrarySearchCommand command) {
+    System.out.println();
+    switch (command) {
+      case TITLE -> {
+        System.out.println("Enter the title to search for: ");
+        System.out.print("title> ");
+        var title = scanner.nextLine();
+        return SearchCriteria.builder().title(title).build();
+      }
+      case AUTHOR -> {
+        System.out.println("Enter the author to search for: ");
+        System.out.print("author> ");
+        var author = scanner.nextLine();
+        return SearchCriteria.builder().author(author).build();
+      }
+      case TYPE -> {
+        System.out.println("Enter the type to search for: ");
+        System.out.print("type> ");
+        var type = scanner.nextLine();
+        return SearchCriteria.builder().type(type).build();
+      }
+      default -> System.out.println("Invalid search command: " + command);
+    }
+    return null;
+  }
+
+  private void printSearchResults(Set<MediaItem> results) {
+    System.out.println();
+
+    if (results.isEmpty()) {
+      System.out.println("No results found.");
+      return;
+    }
+
+    System.out.println("Search results:\n");
+    for (MediaItem item : results) {
+      System.out.println("ID: " + item.getId());
+      System.out.println("TITLE: " + item.getTitle());
+      if (item instanceof Book book) {
+        System.out.println("AUTHOR(S): " + String.join(", ", book.getAuthors()));
+      }
+      System.out.println("TYPE: " + item.getType().toUpperCase());
+      System.out.println();
+    }
+    System.out.println("Found " + results.size() + " result(s).\n");
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryCommand.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryCommand.java
new file mode 100644
index 000000000..2d49d5592
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibraryCommand.java
@@ -0,0 +1,28 @@
+package com.codedifferently.lesson25.cli;
+
+public enum LibraryCommand {
+  UNKNOWN(0),
+  EXIT(1),
+  SEARCH(2),
+  CHECKOUT(3),
+  RETURN(4);
+
+  private final int value;
+
+  LibraryCommand(int value) {
+    this.value = value;
+  }
+
+  public int getValue() {
+    return value;
+  }
+
+  public static LibraryCommand fromValue(int value) {
+    for (LibraryCommand command : LibraryCommand.values()) {
+      if (command.getValue() == value) {
+        return command;
+      }
+    }
+    return UNKNOWN;
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibrarySearchCommand.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibrarySearchCommand.java
new file mode 100644
index 000000000..df180eaa5
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/cli/LibrarySearchCommand.java
@@ -0,0 +1,28 @@
+package com.codedifferently.lesson25.cli;
+
+public enum LibrarySearchCommand {
+  UNKNOWN(0),
+  RETURN(1),
+  TITLE(2),
+  AUTHOR(3),
+  TYPE(4);
+
+  private final int value;
+
+  LibrarySearchCommand(int value) {
+    this.value = value;
+  }
+
+  public int getValue() {
+    return value;
+  }
+
+  public static LibrarySearchCommand fromValue(int value) {
+    for (LibrarySearchCommand criteria : LibrarySearchCommand.values()) {
+      if (criteria.getValue() == value) {
+        return criteria;
+      }
+    }
+    return UNKNOWN;
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryCsvDataLoader.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryCsvDataLoader.java
new file mode 100644
index 000000000..4c3f99049
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryCsvDataLoader.java
@@ -0,0 +1,126 @@
+package com.codedifferently.lesson25.factory;
+
+import com.codedifferently.lesson25.models.CheckoutModel;
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import com.codedifferently.lesson25.models.LibraryGuestModel;
+import com.codedifferently.lesson25.models.MediaItemModel;
+import java.io.FileReader;
+import java.io.IOException;
+import java.time.Instant;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+import org.apache.commons.csv.CSVFormat;
+import org.apache.commons.csv.CSVRecord;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.stereotype.Service;
+
+/** An object that loads data from a CSV and returns a LibraryDataModel object. */
+@Service
+public final class LibraryCsvDataLoader implements LibraryDataLoader {
+
+  private static final String MEDIA_ITEMS_CSV_PATH = "csv/media_items.csv";
+  private static final String GUESTS_CSV_PATH = "csv/guests.csv";
+  private static final String CHECKED_OUT_ITEMS_CSV_PATH = "csv/checked_out_items.csv";
+
+  @Override
+  public LibraryDataModel loadData() throws IOException {
+    var model = new LibraryDataModel();
+    model.mediaItems = loadMediaItemsFromCsv(MEDIA_ITEMS_CSV_PATH);
+    model.guests = loadGuestsFromCsv(GUESTS_CSV_PATH, CHECKED_OUT_ITEMS_CSV_PATH);
+    return model;
+  }
+
+  private List<MediaItemModel> loadMediaItemsFromCsv(String filePath) throws IOException {
+    List<MediaItemModel> mediaItems = new ArrayList<>();
+
+    try (var reader = new FileReader(new ClassPathResource(filePath).getFile());
+        var csvParser = CSVFormat.DEFAULT.withFirstRecordAsHeader().parse(reader)) {
+      for (CSVRecord csvRecord : csvParser) {
+        var item = new MediaItemModel();
+
+        item.type = csvRecord.get("type");
+        item.id = UUID.fromString(csvRecord.get("id"));
+        item.title = csvRecord.get("title");
+        item.isbn = csvRecord.get("isbn");
+        item.authors = List.of(csvRecord.get("authors").split(", "));
+        item.pages = parseIntOrDefault(csvRecord.get("pages"), 0);
+        item.runtime = parseIntOrDefault(csvRecord.get("runtime"), 0);
+        item.edition = csvRecord.get("edition");
+
+        mediaItems.add(item);
+      }
+
+    } catch (IOException e) {
+      return new ArrayList<>();
+    }
+
+    return mediaItems;
+  }
+
+  private int parseIntOrDefault(String value, int defaultVal) {
+    try {
+      return Integer.parseInt(value);
+    } catch (NumberFormatException e) {
+      return defaultVal;
+    }
+  }
+
+  private List<LibraryGuestModel> loadGuestsFromCsv(
+      String guestsCsvPath, String checkedOutCsvPath) {
+    List<LibraryGuestModel> guests = loadGuestRecordsFromCsv(guestsCsvPath);
+    Map<String, List<CheckoutModel>> checkedOutItems = loadCheckoutsFromCsv(checkedOutCsvPath);
+    for (LibraryGuestModel guest : guests) {
+      if (checkedOutItems.containsKey(guest.email)) {
+        guest.checkedOutItems = checkedOutItems.get(guest.email);
+      } else {
+        guest.checkedOutItems = new ArrayList<>();
+      }
+    }
+    return guests;
+  }
+
+  private List<LibraryGuestModel> loadGuestRecordsFromCsv(String guestsCsvPath) {
+    List<LibraryGuestModel> guests = new ArrayList<>();
+
+    try (var reader = new FileReader(new ClassPathResource(guestsCsvPath).getFile());
+        var csvParser = CSVFormat.DEFAULT.withFirstRecordAsHeader().parse(reader)) {
+      for (CSVRecord csvRecord : csvParser) {
+        var guest = new LibraryGuestModel();
+
+        guest.type = csvRecord.get("type");
+        guest.name = csvRecord.get("name");
+        guest.email = csvRecord.get("email");
+
+        guests.add(guest);
+      }
+    } catch (IOException e) {
+      return new ArrayList<>();
+    }
+
+    return guests;
+  }
+
+  private Map<String, List<CheckoutModel>> loadCheckoutsFromCsv(String checkedOutCsvPath) {
+    Map<String, List<CheckoutModel>> checkoutsByGuestEmail = new HashMap<>();
+
+    try (var reader = new FileReader(new ClassPathResource(checkedOutCsvPath).getFile());
+        var csvParser = CSVFormat.DEFAULT.withFirstRecordAsHeader().parse(reader)) {
+      for (CSVRecord csvRecord : csvParser) {
+        var checkout = new CheckoutModel();
+
+        checkout.itemId = UUID.fromString(csvRecord.get("item_id"));
+        checkout.dueDate = Instant.parse(csvRecord.get("due_date"));
+
+        String guestEmail = csvRecord.get("email");
+        checkoutsByGuestEmail.computeIfAbsent(guestEmail, e -> new ArrayList<>()).add(checkout);
+      }
+    } catch (IOException e) {
+      return new HashMap<>();
+    }
+
+    return checkoutsByGuestEmail;
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryDataLoader.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryDataLoader.java
new file mode 100644
index 000000000..99fb7fb58
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryDataLoader.java
@@ -0,0 +1,16 @@
+package com.codedifferently.lesson25.factory;
+
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import java.io.IOException;
+
+/** An object that loads data from a source and returns a LibraryDataModel object. */
+public interface LibraryDataLoader {
+
+  /**
+   * Load data from a source and return a LibraryDataModel object.
+   *
+   * @return A LibraryDataModel object.
+   * @throws IOException if an I/O error occurs.
+   */
+  public LibraryDataModel loadData() throws IOException;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryDbDataLoader.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryDbDataLoader.java
new file mode 100644
index 000000000..b897de124
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryDbDataLoader.java
@@ -0,0 +1,26 @@
+package com.codedifferently.lesson25.factory;
+
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import com.codedifferently.lesson25.repository.LibraryGuestRepository;
+import com.codedifferently.lesson25.repository.MediaItemRepository;
+import java.io.IOException;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.stereotype.Service;
+
+/** A data loader that loads library data from a database. */
+@Service
+public final class LibraryDbDataLoader implements LibraryDataLoader {
+
+  @Autowired private MediaItemRepository mediaItemsRepository;
+  @Autowired private LibraryGuestRepository libraryGuestRepository;
+
+  @Override
+  public LibraryDataModel loadData() throws IOException {
+    var model = new LibraryDataModel();
+
+    model.mediaItems = mediaItemsRepository.findAll();
+    model.guests = libraryGuestRepository.findAll();
+
+    return model;
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryFactory.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryFactory.java
new file mode 100644
index 000000000..c1b892308
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryFactory.java
@@ -0,0 +1,103 @@
+package com.codedifferently.lesson25.factory;
+
+import com.codedifferently.lesson25.library.Librarian;
+import com.codedifferently.lesson25.library.Library;
+import com.codedifferently.lesson25.library.LibraryGuest;
+import com.codedifferently.lesson25.library.MediaItem;
+import com.codedifferently.lesson25.models.CheckoutModel;
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.UUID;
+
+/** A factory class that creates a Library object with a LibraryDataLoader object. */
+public final class LibraryFactory {
+
+  /**
+   * Create a Library object with a LibraryDataLoader object.
+   *
+   * @param loader A LibraryDataLoader object.
+   * @return A Library object.
+   * @throws IOException
+   */
+  public static Library createWithLoader(LibraryDataLoader loader) throws IOException {
+    Library library = new Library("main-library");
+
+    // Load library data.
+    LibraryDataModel data = loader.loadData();
+
+    // Add guests to the library.
+    List<LibraryGuest> guests = data.getGuests();
+    addLibraryGuests(library, guests);
+
+    // Add library items using the first librarian.
+    Librarian firstLibrarian = findFirstLibrarian(guests);
+    List<MediaItem> mediaItems = data.getMediaItems();
+    addLibraryItems(library, mediaItems, firstLibrarian);
+
+    // Check out items from the library.
+    Map<String, List<CheckoutModel>> checkoutsByEmail = data.getCheckoutsByEmail();
+    Map<UUID, MediaItem> mediaItemById = getMediaItemsById(mediaItems);
+    Map<String, LibraryGuest> guestsByEmail = getGuestsByEmail(guests);
+    checkOutItems(library, checkoutsByEmail, guestsByEmail, mediaItemById);
+
+    return library;
+  }
+
+  private static Map<UUID, MediaItem> getMediaItemsById(List<MediaItem> mediaItems) {
+    Map<UUID, MediaItem> mediaItemById = new HashMap<>();
+    for (MediaItem mediaItem : mediaItems) {
+      mediaItemById.put(mediaItem.getId(), mediaItem);
+    }
+    return mediaItemById;
+  }
+
+  private static Librarian findFirstLibrarian(List<LibraryGuest> guests) {
+    Librarian firstLibrarian = null;
+    for (LibraryGuest guest : guests) {
+      if (guest instanceof Librarian librarian) {
+        firstLibrarian = librarian;
+      }
+    }
+    return firstLibrarian;
+  }
+
+  private static void addLibraryGuests(Library library, List<LibraryGuest> guests) {
+    for (LibraryGuest guest : guests) {
+      library.addLibraryGuest(guest);
+    }
+  }
+
+  private static void addLibraryItems(
+      Library library, List<MediaItem> mediaItems, Librarian firstLibrarian) {
+    for (MediaItem mediaItem : mediaItems) {
+      library.addMediaItem(mediaItem, firstLibrarian);
+    }
+  }
+
+  private static Map<String, LibraryGuest> getGuestsByEmail(List<LibraryGuest> guests) {
+    Map<String, LibraryGuest> guestByEmail = new HashMap<>();
+    for (LibraryGuest guest : guests) {
+      guestByEmail.put(guest.getEmail(), guest);
+    }
+    return guestByEmail;
+  }
+
+  private static void checkOutItems(
+      Library library,
+      Map<String, List<CheckoutModel>> checkoutsByEmail,
+      Map<String, LibraryGuest> guestByEmail,
+      Map<UUID, MediaItem> mediaItemById) {
+    for (var entry : checkoutsByEmail.entrySet()) {
+      String email = entry.getKey();
+      List<CheckoutModel> checkouts = entry.getValue();
+      LibraryGuest guest = guestByEmail.get(email);
+      for (CheckoutModel checkout : checkouts) {
+        MediaItem mediaItem = mediaItemById.get(checkout.itemId);
+        library.checkOutMediaItem(mediaItem, guest);
+      }
+    }
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryJsonDataLoader.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryJsonDataLoader.java
new file mode 100644
index 000000000..e512df156
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/factory/LibraryJsonDataLoader.java
@@ -0,0 +1,24 @@
+package com.codedifferently.lesson25.factory;
+
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
+import java.io.File;
+import java.io.IOException;
+import org.springframework.core.io.ClassPathResource;
+import org.springframework.stereotype.Service;
+
+/** Loads data from a JSON file and returns a LibraryDataModel object. */
+@Service
+public final class LibraryJsonDataLoader implements LibraryDataLoader {
+
+  @Override
+  public LibraryDataModel loadData() throws IOException {
+    ObjectMapper objectMapper = new ObjectMapper();
+    objectMapper.registerModule(new JavaTimeModule());
+
+    // Load data from data.json file
+    File file = new ClassPathResource("json/data.json").getFile();
+    return objectMapper.readValue(file, LibraryDataModel.class);
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Book.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Book.java
new file mode 100644
index 000000000..906ab3aaf
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Book.java
@@ -0,0 +1,78 @@
+package com.codedifferently.lesson25.library;
+
+import java.util.List;
+import java.util.UUID;
+
+/** Represents a book. */
+public class Book extends MediaItemBase {
+
+  private final String isbn;
+  private final List<String> authors;
+  private final int numberOfPages;
+
+  /**
+   * Create a new book with the given title, ISBN, authors, and number of pages.
+   *
+   * @param id The ID of the book.
+   * @param title The title of the book.
+   * @param isbn The ISBN of the book.
+   * @param authors The authors of the book.
+   * @param numberOfPages The number of pages in the book.
+   */
+  public Book(UUID id, String title, String isbn, List<String> authors, int numberOfPages) {
+    super(id, title);
+    this.isbn = isbn;
+    this.authors = authors;
+    this.numberOfPages = numberOfPages;
+  }
+
+  @Override
+  public String getType() {
+    return "book";
+  }
+
+  /**
+   * Get the ISBN of the book.
+   *
+   * @return The ISBN of the book.
+   */
+  public String getIsbn() {
+    return this.isbn;
+  }
+
+  /**
+   * Get the authors of the book.
+   *
+   * @return The authors of the book.
+   */
+  public List<String> getAuthors() {
+    return this.authors;
+  }
+
+  /**
+   * Get the number of pages in the book.
+   *
+   * @return The number of pages in the book.
+   */
+  public int getNumberOfPages() {
+    return this.numberOfPages;
+  }
+
+  @Override
+  protected boolean matchesAuthor(String authorQuery) {
+    if (authorQuery == null) {
+      return true;
+    }
+    for (String author : this.getAuthors()) {
+      if (author.toLowerCase().contains(authorQuery.toLowerCase())) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  @Override
+  public String toString() {
+    return "Book{" + "id='" + getId() + '\'' + ", title='" + getTitle() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Dvd.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Dvd.java
new file mode 100644
index 000000000..5653559cb
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Dvd.java
@@ -0,0 +1,21 @@
+package com.codedifferently.lesson25.library;
+
+import java.util.UUID;
+
+/** Represents a DVD. */
+public class Dvd extends MediaItemBase {
+
+  public Dvd(UUID id, String title) {
+    super(id, title);
+  }
+
+  @Override
+  public String getType() {
+    return "dvd";
+  }
+
+  @Override
+  public String toString() {
+    return "Dvd{" + "id='" + getId() + '\'' + ", title='" + getTitle() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Librarian.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Librarian.java
new file mode 100644
index 000000000..c67274724
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Librarian.java
@@ -0,0 +1,14 @@
+package com.codedifferently.lesson25.library;
+
+/** Represents a librarian of a library. */
+public class Librarian extends LibraryGuestBase {
+
+  public Librarian(String name, String email) {
+    super(name, email);
+  }
+
+  @Override
+  public String toString() {
+    return "Librarian{" + "id='" + getId() + '\'' + ", name='" + getName() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Library.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Library.java
new file mode 100644
index 000000000..cc40595be
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Library.java
@@ -0,0 +1,224 @@
+package com.codedifferently.lesson25.library;
+
+import com.codedifferently.lesson25.library.exceptions.MediaItemCheckedOutException;
+import com.codedifferently.lesson25.library.search.CatalogSearcher;
+import com.codedifferently.lesson25.library.search.SearchCriteria;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Set;
+import java.util.UUID;
+
+/** Represents a library. */
+public class Library {
+
+  private final Map<UUID, MediaItem> itemsById = new HashMap<>();
+  private final Set<UUID> checkedOutItemIds = new HashSet<>();
+  private final Map<String, Set<MediaItem>> checkedOutItemsByGuest = new HashMap<>();
+  private final Map<String, LibraryGuest> guestsById = new HashMap<>();
+  private final String id;
+  private final CatalogSearcher<MediaItem> searcher;
+
+  /**
+   * Create a new library with the given id.
+   *
+   * @param id The id of the library.
+   */
+  public Library(String id) {
+    this.id = id;
+    this.searcher = new CatalogSearcher(this.itemsById.values());
+  }
+
+  /**
+   * Get the id of the library.
+   *
+   * @return The id of the library.
+   */
+  public String getId() {
+    return this.id;
+  }
+
+  /**
+   * Add a item to the library.
+   *
+   * @param item The item to add.
+   * @param librarian The librarian adding the item.
+   */
+  public void addMediaItem(MediaItem item, Librarian librarian) {
+    this.itemsById.put(item.getId(), item);
+    item.setLibrary(this);
+  }
+
+  /**
+   * Remove a item from the library.
+   *
+   * @param item The item to remove.
+   * @param librarian The librarian removing the item.
+   */
+  public void removeMediaItem(MediaItem item, Librarian librarian)
+      throws MediaItemCheckedOutException {
+    if (this.isCheckedOut(item)) {
+      throw new MediaItemCheckedOutException("Cannot remove checked out item.");
+    }
+    this.itemsById.remove(item.getId());
+    item.setLibrary(null);
+  }
+
+  /**
+   * Search the library for items matching the given query.
+   *
+   * @param query The query to search for.
+   * @return The items matching the query.
+   */
+  public Set<MediaItem> search(SearchCriteria query) {
+    return new HashSet<>(this.searcher.search(query));
+  }
+
+  /**
+   * Add a guest to the library.
+   *
+   * @param guest The guest to add.
+   */
+  public void addLibraryGuest(LibraryGuest guest) {
+    this.guestsById.put(guest.getId(), guest);
+    this.checkedOutItemsByGuest.put(guest.getId(), new HashSet<>());
+    guest.setLibrary(this);
+  }
+
+  /**
+   * Remove a guest from the library.
+   *
+   * @param guest The guest to remove.
+   */
+  public void removeLibraryGuest(LibraryGuest guest) throws MediaItemCheckedOutException {
+    if (!this.checkedOutItemsByGuest.get(guest.getId()).isEmpty()) {
+      throw new MediaItemCheckedOutException("Cannot remove guest with checked out items.");
+    }
+    this.guestsById.remove(guest.getId());
+    this.checkedOutItemsByGuest.remove(guest.getId());
+    guest.setLibrary(null);
+  }
+
+  /**
+   * Check out a item to a guest.
+   *
+   * @param item The item to check out.
+   * @param guest The guest to check out the item to.
+   * @return True if the item was checked out, false otherwise.
+   */
+  public boolean checkOutMediaItem(MediaItem item, LibraryGuest guest) {
+    if (!this.canCheckOutMediaItem(item, guest)) {
+      return false;
+    }
+    this.checkedOutItemIds.add(item.getId());
+    this.checkedOutItemsByGuest.get(guest.getId()).add(item);
+    return true;
+  }
+
+  private boolean canCheckOutMediaItem(MediaItem item, LibraryGuest guest) {
+    if (!item.canCheckOut()) {
+      return false;
+    }
+    if (!this.hasMediaItem(item)) {
+      return false;
+    }
+    if (this.isCheckedOut(item)) {
+      return false;
+    }
+    return this.hasLibraryGuest(guest);
+  }
+
+  /**
+   * Check if the library has the given item.
+   *
+   * @param item The item to check for.
+   * @return True if the library has the item, false otherwise.
+   */
+  public boolean hasMediaItem(MediaItem item) {
+    return this.itemsById.containsKey(item.getId());
+  }
+
+  /**
+   * Check if the given item is checked out.
+   *
+   * @param item The item to check.
+   * @return True if the item is checked out, false otherwise.
+   */
+  public boolean isCheckedOut(MediaItem item) {
+    return this.checkedOutItemIds.contains(item.getId());
+  }
+
+  /**
+   * Check if the library has the given guest.
+   *
+   * @param guest The guest to check for.
+   * @return True if the library has the guest, false otherwise.
+   */
+  public boolean hasLibraryGuest(LibraryGuest guest) {
+    return this.guestsById.containsKey(guest.getId());
+  }
+
+  /**
+   * Return a item to the library.
+   *
+   * @param item The item to return.
+   * @param guest The guest returning the item.
+   * @return True if the item was returned, false otherwise.
+   */
+  public boolean checkInMediaItem(MediaItem item, LibraryGuest guest) {
+    if (!this.hasMediaItem(item)) {
+      return false;
+    }
+    this.checkedOutItemIds.remove(item.getId());
+    this.checkedOutItemsByGuest.get(guest.getId()).remove(item);
+    return true;
+  }
+
+  /**
+   * Get the items checked out by a guest.
+   *
+   * @param guest The guest to get the items for.
+   * @return The items checked out by the guest.
+   */
+  public Set<MediaItem> getCheckedOutByGuest(LibraryGuest guest) {
+    return this.checkedOutItemsByGuest.get(guest.getId());
+  }
+
+  /**
+   * Get a snapshot of the library info.
+   *
+   * @return The library info.
+   */
+  public LibraryInfo getInfo() {
+    Map<String, Set<MediaItem>> itemsByGuest =
+        this.checkedOutItemsByGuest.entrySet().stream()
+            .collect(
+                HashMap::new,
+                (map, entry) ->
+                    map.put(
+                        entry.getKey(),
+                        Collections.unmodifiableSet(new HashSet<>(entry.getValue()))),
+                HashMap::putAll);
+    return LibraryInfo.builder()
+        .id(this.id)
+        .items(Collections.unmodifiableSet(new HashSet<>(this.itemsById.values())))
+        .guests(Collections.unmodifiableSet(new HashSet<>(this.guestsById.values())))
+        .checkedOutItemsByGuest(Collections.unmodifiableMap(itemsByGuest))
+        .build();
+  }
+
+  @Override
+  public String toString() {
+    return "Library{"
+        + "itemsById="
+        + itemsById
+        + ", checkedOutItemIds="
+        + checkedOutItemIds
+        + ", checkedOutMediaItemsByLibraryGuest="
+        + checkedOutItemsByGuest
+        + ", guestIds="
+        + guestsById
+        + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryGuest.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryGuest.java
new file mode 100644
index 000000000..274f9db6b
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryGuest.java
@@ -0,0 +1,45 @@
+package com.codedifferently.lesson25.library;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import java.util.Set;
+
+public interface LibraryGuest {
+
+  /**
+   * Get the library that the guest is in.
+   *
+   * @param library The library that the guest is in.
+   * @throws WrongLibraryException If the guest is not in the library.
+   */
+  public void setLibrary(Library library) throws WrongLibraryException;
+
+  /**
+   * Get the name of the guest.
+   *
+   * @return The name of the guest.
+   */
+  public String getName();
+
+  /**
+   * Get the email of the guest.
+   *
+   * @return The email of the guest.
+   */
+  public String getEmail();
+
+  /**
+   * Get the id of the guest.
+   *
+   * @return The id of the guest.
+   */
+  public String getId();
+
+  /**
+   * Gets the items currently checked out to the guest.
+   *
+   * @return The items currently checked out to the guest.
+   * @throws LibraryNotSetException If the library is not set for the guest.
+   */
+  public Set<MediaItem> getCheckedOutMediaItems() throws LibraryNotSetException;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryGuestBase.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryGuestBase.java
new file mode 100644
index 000000000..6e1cccdfe
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryGuestBase.java
@@ -0,0 +1,73 @@
+package com.codedifferently.lesson25.library;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import java.util.Objects;
+import java.util.Set;
+
+/** Base implementation of a library guest. */
+public class LibraryGuestBase implements LibraryGuest {
+
+  private Library library;
+  private final String name;
+  private final String email;
+
+  public LibraryGuestBase(String name, String email) {
+    this.name = name;
+    this.email = email;
+  }
+
+  @Override
+  public void setLibrary(Library library) throws WrongLibraryException {
+    if (library != null && !library.hasLibraryGuest(this)) {
+      throw new WrongLibraryException(
+          "Patron " + this.getId() + " is not in library " + library.getId());
+    }
+    this.library = library;
+  }
+
+  @Override
+  public String getName() {
+    return this.name;
+  }
+
+  @Override
+  public String getEmail() {
+    return this.email;
+  }
+
+  @Override
+  public String getId() {
+    return this.email;
+  }
+
+  @Override
+  public Set<MediaItem> getCheckedOutMediaItems() throws LibraryNotSetException {
+    if (this.library == null) {
+      throw new LibraryNotSetException("Library not set for patron " + this.getId());
+    }
+    return this.library.getCheckedOutByGuest(this);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof LibraryGuestBase)) {
+      return false;
+    }
+    LibraryGuestBase guest = (LibraryGuestBase) o;
+    return Objects.equals(getId(), guest.getId());
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(getId());
+  }
+
+  @Override
+  public String toString() {
+    return "LibraryGuestBase{" + "id='" + getId() + '\'' + ", name='" + getName() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryInfo.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryInfo.java
new file mode 100644
index 000000000..49b4d23de
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/LibraryInfo.java
@@ -0,0 +1,20 @@
+package com.codedifferently.lesson25.library;
+
+import java.util.Map;
+import java.util.Set;
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@Builder
+@NoArgsConstructor
+@AllArgsConstructor
+public class LibraryInfo {
+
+  public String id;
+  public Set<MediaItem> items;
+  public Set<LibraryGuest> guests;
+  public Map<String, Set<MediaItem>> checkedOutItemsByGuest;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Magazine.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Magazine.java
new file mode 100644
index 000000000..53aa49bd1
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Magazine.java
@@ -0,0 +1,26 @@
+package com.codedifferently.lesson25.library;
+
+import java.util.UUID;
+
+/** Represents a magazine. */
+public class Magazine extends MediaItemBase {
+
+  public Magazine(UUID id, String title) {
+    super(id, title);
+  }
+
+  @Override
+  public String getType() {
+    return "magazine";
+  }
+
+  @Override
+  public boolean canCheckOut() {
+    return false;
+  }
+
+  @Override
+  public String toString() {
+    return "Magazine{" + "id='" + getId() + '\'' + ", title='" + getTitle() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/MediaItem.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/MediaItem.java
new file mode 100644
index 000000000..f87da2aeb
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/MediaItem.java
@@ -0,0 +1,54 @@
+package com.codedifferently.lesson25.library;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import com.codedifferently.lesson25.library.search.Searchable;
+import java.util.UUID;
+
+/** Represents a media item. */
+public interface MediaItem extends Searchable {
+
+  /**
+   * Get the type of the media item.
+   *
+   * @return The type of the media item.
+   */
+  public String getType();
+
+  /**
+   * Get the id of the media item.
+   *
+   * @return The id of the media item.
+   */
+  public UUID getId();
+
+  /**
+   * Set the library that the media item is in.
+   *
+   * @param library
+   * @throws WrongLibraryException
+   */
+  public void setLibrary(Library library) throws WrongLibraryException;
+
+  /**
+   * Get the title of the media item.
+   *
+   * @return The title of the media item.
+   */
+  public String getTitle();
+
+  /**
+   * Check if the media item is checked out.
+   *
+   * @return True if the media item is checked out, false otherwise.
+   * @throws LibraryNotSetException
+   */
+  public boolean isCheckedOut() throws LibraryNotSetException;
+
+  /**
+   * Check if the media item can be checked out.
+   *
+   * @return True if the media item can be checked out, false otherwise.
+   */
+  public boolean canCheckOut();
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/MediaItemBase.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/MediaItemBase.java
new file mode 100644
index 000000000..6438827e2
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/MediaItemBase.java
@@ -0,0 +1,98 @@
+package com.codedifferently.lesson25.library;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import com.codedifferently.lesson25.library.search.SearchCriteria;
+import java.util.Objects;
+import java.util.UUID;
+
+/** Base implementation of a media item. */
+public abstract class MediaItemBase implements MediaItem {
+
+  private Library library;
+  private final UUID id;
+  private final String title;
+
+  public MediaItemBase(UUID id, String title) {
+    this.id = id;
+    this.title = title;
+  }
+
+  @Override
+  public UUID getId() {
+    return id;
+  }
+
+  @Override
+  public String getTitle() {
+    return title;
+  }
+
+  @Override
+  public void setLibrary(Library library) throws WrongLibraryException {
+    if (library != null && !library.hasMediaItem(this)) {
+      throw new WrongLibraryException(
+          "Media item " + this.getId() + " is not in library " + library.getId());
+    }
+    this.library = library;
+  }
+
+  @Override
+  public boolean isCheckedOut() throws LibraryNotSetException {
+    if (this.library == null) {
+      throw new LibraryNotSetException("Library not set for item " + this.getId());
+    }
+    return library.isCheckedOut(this);
+  }
+
+  @Override
+  public boolean canCheckOut() {
+    return true;
+  }
+
+  /**
+   * Check if the media item matches the given author.
+   *
+   * @param author The author to check.
+   * @return True if the media item matches the author, false otherwise.
+   */
+  protected boolean matchesAuthor(String author) {
+    return false;
+  }
+
+  @Override
+  public boolean matches(SearchCriteria query) {
+    if (query.id != null && !this.getId().toString().equalsIgnoreCase(query.id)) {
+      return false;
+    }
+    if (query.title != null && !this.getTitle().toLowerCase().contains(query.title.toLowerCase())) {
+      return false;
+    }
+    if (query.type != null && !this.getType().equalsIgnoreCase(query.type)) {
+      return false;
+    }
+    return query.author == null || this.matchesAuthor(query.author);
+  }
+
+  @Override
+  public boolean equals(Object o) {
+    if (this == o) {
+      return true;
+    }
+    if (!(o instanceof MediaItem)) {
+      return false;
+    }
+    MediaItem item = (MediaItem) o;
+    return Objects.equals(getId(), item.getId());
+  }
+
+  @Override
+  public int hashCode() {
+    return Objects.hash(getId());
+  }
+
+  @Override
+  public String toString() {
+    return "MediaItem{" + "id='" + getId() + '\'' + ", title='" + getTitle() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Newspaper.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Newspaper.java
new file mode 100644
index 000000000..2c25624f1
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Newspaper.java
@@ -0,0 +1,26 @@
+package com.codedifferently.lesson25.library;
+
+import java.util.UUID;
+
+/** Represents a newspaper. */
+public class Newspaper extends MediaItemBase {
+
+  public Newspaper(UUID id, String title) {
+    super(id, title);
+  }
+
+  @Override
+  public String getType() {
+    return "newspaper";
+  }
+
+  @Override
+  public boolean canCheckOut() {
+    return false;
+  }
+
+  @Override
+  public String toString() {
+    return "Newspaper{" + "id='" + getId() + '\'' + ", title='" + getTitle() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Patron.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Patron.java
new file mode 100644
index 000000000..750bc5d71
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/Patron.java
@@ -0,0 +1,20 @@
+package com.codedifferently.lesson25.library;
+
+/** Represents a patron of a library. */
+public class Patron extends LibraryGuestBase {
+
+  /**
+   * Create a new patron with the given name and email.
+   *
+   * @param name The name of the patron.
+   * @param email The email of the patron.
+   */
+  public Patron(String name, String email) {
+    super(name, email);
+  }
+
+  @Override
+  public String toString() {
+    return "Patron{" + "id='" + getId() + '\'' + ", name='" + getName() + '\'' + '}';
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/LibraryNotSetException.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/LibraryNotSetException.java
new file mode 100644
index 000000000..4c336b9e8
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/LibraryNotSetException.java
@@ -0,0 +1,8 @@
+package com.codedifferently.lesson25.library.exceptions;
+
+public class LibraryNotSetException extends RuntimeException {
+
+  public LibraryNotSetException(String message) {
+    super(message);
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/MediaItemCheckedOutException.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/MediaItemCheckedOutException.java
new file mode 100644
index 000000000..2ea953a63
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/MediaItemCheckedOutException.java
@@ -0,0 +1,8 @@
+package com.codedifferently.lesson25.library.exceptions;
+
+public class MediaItemCheckedOutException extends RuntimeException {
+
+  public MediaItemCheckedOutException(String message) {
+    super(message);
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/WrongLibraryException.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/WrongLibraryException.java
new file mode 100644
index 000000000..110e3fa93
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/exceptions/WrongLibraryException.java
@@ -0,0 +1,8 @@
+package com.codedifferently.lesson25.library.exceptions;
+
+public class WrongLibraryException extends RuntimeException {
+
+  public WrongLibraryException(String message) {
+    super(message);
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/CatalogSearcher.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/CatalogSearcher.java
new file mode 100644
index 000000000..6101120aa
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/CatalogSearcher.java
@@ -0,0 +1,32 @@
+package com.codedifferently.lesson25.library.search;
+
+import java.util.Collection;
+
+/**
+ * Searches a catalog for items that match a query.
+ *
+ * @param <T>
+ */
+public class CatalogSearcher<T extends Searchable> {
+
+  private final Collection<T> catalog;
+
+  /**
+   * Constructor for CatalogSearcher
+   *
+   * @param catalog
+   */
+  public CatalogSearcher(Collection<T> catalog) {
+    this.catalog = catalog;
+  }
+
+  /**
+   * Searches the catalog for items that match the given query.
+   *
+   * @param query The query to search for.
+   * @return The items that match the query.
+   */
+  public Collection<T> search(SearchCriteria query) {
+    return catalog.stream().filter(item -> item.matches(query)).toList();
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/SearchCriteria.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/SearchCriteria.java
new file mode 100644
index 000000000..0480aa448
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/SearchCriteria.java
@@ -0,0 +1,25 @@
+package com.codedifferently.lesson25.library.search;
+
+import lombok.AllArgsConstructor;
+import lombok.Builder;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+
+@Data
+@Builder
+@AllArgsConstructor
+@NoArgsConstructor
+public class SearchCriteria {
+
+  /** The ID to search for (exact match). */
+  public String id;
+
+  /** The title to search for. */
+  public String title;
+
+  /** The author to search for. */
+  public String author;
+
+  /** The type to search for (exact match). */
+  public String type;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/Searchable.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/Searchable.java
new file mode 100644
index 000000000..83b1ce181
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/library/search/Searchable.java
@@ -0,0 +1,12 @@
+package com.codedifferently.lesson25.library.search;
+
+public interface Searchable {
+
+  /**
+   * Indicates whether an item matches the search criteria.
+   *
+   * @param query The query to search for.
+   * @return The items that match the query.
+   */
+  boolean matches(SearchCriteria query);
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/AuthorsConverter.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/AuthorsConverter.java
new file mode 100644
index 000000000..f198f819f
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/AuthorsConverter.java
@@ -0,0 +1,18 @@
+package com.codedifferently.lesson25.models;
+
+import jakarta.persistence.AttributeConverter;
+import jakarta.persistence.Converter;
+import java.util.List;
+
+@Converter
+public class AuthorsConverter implements AttributeConverter<List<String>, String> {
+  @Override
+  public String convertToDatabaseColumn(List<String> authors) {
+    return String.join(", ", authors);
+  }
+
+  @Override
+  public List<String> convertToEntityAttribute(String authors) {
+    return authors != null ? List.of(authors.split(", ")) : List.of();
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/CheckoutModel.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/CheckoutModel.java
new file mode 100644
index 000000000..ae8ac1c20
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/CheckoutModel.java
@@ -0,0 +1,16 @@
+package com.codedifferently.lesson25.models;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+import java.time.Instant;
+import java.util.UUID;
+
+@Entity
+@Table(name = "checked_out_items")
+public class CheckoutModel {
+
+  @Id public UUID itemId;
+  public String email;
+  public Instant dueDate;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/LibraryDataModel.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/LibraryDataModel.java
new file mode 100644
index 000000000..6c268f962
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/LibraryDataModel.java
@@ -0,0 +1,62 @@
+package com.codedifferently.lesson25.models;
+
+import com.codedifferently.lesson25.library.Book;
+import com.codedifferently.lesson25.library.Dvd;
+import com.codedifferently.lesson25.library.Librarian;
+import com.codedifferently.lesson25.library.LibraryGuest;
+import com.codedifferently.lesson25.library.Magazine;
+import com.codedifferently.lesson25.library.MediaItem;
+import com.codedifferently.lesson25.library.Newspaper;
+import com.codedifferently.lesson25.library.Patron;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
+public class LibraryDataModel {
+
+  public List<MediaItemModel> mediaItems;
+  public List<LibraryGuestModel> guests;
+
+  public List<MediaItem> getMediaItems() {
+    List<MediaItem> results = new ArrayList<>();
+    for (MediaItemModel mediaItemModel : mediaItems) {
+      switch (mediaItemModel.type) {
+        case "book" ->
+            results.add(
+                new Book(
+                    mediaItemModel.id,
+                    mediaItemModel.title,
+                    mediaItemModel.isbn,
+                    mediaItemModel.authors,
+                    mediaItemModel.pages));
+        case "dvd" -> results.add(new Dvd(mediaItemModel.id, mediaItemModel.title));
+        case "magazine" -> results.add(new Magazine(mediaItemModel.id, mediaItemModel.title));
+        case "newspaper" -> results.add(new Newspaper(mediaItemModel.id, mediaItemModel.title));
+        default ->
+            throw new IllegalArgumentException("Unknown media item type: " + mediaItemModel.type);
+      }
+    }
+    return results;
+  }
+
+  public List<LibraryGuest> getGuests() {
+    List<LibraryGuest> results = new ArrayList<>();
+    for (LibraryGuestModel guestModel : this.guests) {
+      switch (guestModel.type) {
+        case "librarian" -> results.add(new Librarian(guestModel.name, guestModel.email));
+        case "patron" -> results.add(new Patron(guestModel.name, guestModel.email));
+        default -> throw new AssertionError();
+      }
+    }
+    return results;
+  }
+
+  public Map<String, List<CheckoutModel>> getCheckoutsByEmail() {
+    Map<String, List<CheckoutModel>> results = new HashMap<>();
+    for (LibraryGuestModel guest : this.guests) {
+      results.put(guest.email, guest.checkedOutItems);
+    }
+    return results;
+  }
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/LibraryGuestModel.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/LibraryGuestModel.java
new file mode 100644
index 000000000..988ba02df
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/LibraryGuestModel.java
@@ -0,0 +1,20 @@
+package com.codedifferently.lesson25.models;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.FetchType;
+import jakarta.persistence.Id;
+import jakarta.persistence.OneToMany;
+import jakarta.persistence.Table;
+import java.util.List;
+
+@Entity
+@Table(name = "guests")
+public class LibraryGuestModel {
+
+  public String type;
+  public String name;
+  @Id public String email;
+
+  @OneToMany(mappedBy = "email", fetch = FetchType.EAGER)
+  public List<CheckoutModel> checkedOutItems;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/MediaItemModel.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/MediaItemModel.java
new file mode 100644
index 000000000..a7591d523
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/models/MediaItemModel.java
@@ -0,0 +1,24 @@
+package com.codedifferently.lesson25.models;
+
+import jakarta.persistence.Convert;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+import java.util.List;
+import java.util.UUID;
+
+@Entity
+@Table(name = "media_items")
+public class MediaItemModel {
+  public String type;
+  @Id public UUID id;
+  public String isbn;
+  public String title;
+
+  @Convert(converter = AuthorsConverter.class)
+  public List<String> authors;
+
+  public String edition;
+  public Integer pages = 0;
+  public Integer runtime = 0;
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/repository/LibraryGuestRepository.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/repository/LibraryGuestRepository.java
new file mode 100644
index 000000000..149ed4be4
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/repository/LibraryGuestRepository.java
@@ -0,0 +1,11 @@
+package com.codedifferently.lesson25.repository;
+
+import com.codedifferently.lesson25.models.LibraryGuestModel;
+import java.util.List;
+import org.springframework.data.repository.CrudRepository;
+
+public interface LibraryGuestRepository extends CrudRepository<LibraryGuestModel, String> {
+
+  @Override
+  List<LibraryGuestModel> findAll();
+}
diff --git a/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/repository/MediaItemRepository.java b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/repository/MediaItemRepository.java
new file mode 100644
index 000000000..e22f31db8
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/java/com/codedifferently/lesson25/repository/MediaItemRepository.java
@@ -0,0 +1,12 @@
+package com.codedifferently.lesson25.repository;
+
+import com.codedifferently.lesson25.models.MediaItemModel;
+import java.util.List;
+import java.util.UUID;
+import org.springframework.data.repository.CrudRepository;
+
+public interface MediaItemRepository extends CrudRepository<MediaItemModel, UUID> {
+
+  @Override
+  List<MediaItemModel> findAll();
+}
diff --git a/lesson_25/db/db_app/src/main/resources/application.yml b/lesson_25/db/db_app/src/main/resources/application.yml
new file mode 100644
index 000000000..fd20667af
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/resources/application.yml
@@ -0,0 +1,7 @@
+spring:
+  jpa:
+    database-platform: org.hibernate.community.dialect.SQLiteDialect
+    generate-ddl: true
+  datasource:
+    url: jdbc:sqlite::resource:sqlite/data.db
+    driver-class-name: org.sqlite.JDBC
\ No newline at end of file
diff --git a/lesson_25/db/db_app/src/main/resources/csv/checked_out_items.csv b/lesson_25/db/db_app/src/main/resources/csv/checked_out_items.csv
new file mode 100644
index 000000000..1c2fffa70
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/resources/csv/checked_out_items.csv
@@ -0,0 +1,5 @@
+email,item_id,due_date
+jane.smith@example.com,e27a4e0d-9664-420d-955e-c0e295d0ce02,2024-04-05T00:00:00Z
+jane.smith@example.com,295ea581-cd61-4319-8b0c-e5c0c03286c5,2024-04-07T00:00:00Z
+alice.johnson@example.com,17dd5d20-98f5-4a26-be09-449fea88a3c3,2024-04-03T00:00:00Z
+alice.johnson@example.com,28e5c91f-0e4b-4be5-abb1-8da01fd5587e,2024-04-06T00:00:00Z
\ No newline at end of file
diff --git a/lesson_25/db/db_app/src/main/resources/csv/guests.csv b/lesson_25/db/db_app/src/main/resources/csv/guests.csv
new file mode 100644
index 000000000..bcc02b051
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/resources/csv/guests.csv
@@ -0,0 +1,6 @@
+type,name,email
+librarian,John Doe,john.doe@fakelibrary.org
+patron,Jane Smith,jane.smith@example.com
+patron,Alice Johnson,alice.johnson@example.com
+librarian,Bob Williams,bob.williams@fakelibrary.org
+patron,Emily Brown,emily.brown@example.com
\ No newline at end of file
diff --git a/lesson_25/db/db_app/src/main/resources/csv/media_items.csv b/lesson_25/db/db_app/src/main/resources/csv/media_items.csv
new file mode 100644
index 000000000..c3f8161d5
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/resources/csv/media_items.csv
@@ -0,0 +1,32 @@
+type,id,title,isbn,authors,pages,runtime,edition
+book,e27a4e0d-9664-420d-955e-c0e295d0ce02,To Kill a Mockingbird,978-0061120084,"Harper Lee",336,,
+book,17dd5d20-98f5-4a26-be09-449fea88a3c3,1984,978-0451524935,"George Orwell",328,,
+dvd,28e5c91f-0e4b-4be5-abb1-8da01fd5587e,The Shawshank Redemption,,,,142,
+dvd,295ea581-cd61-4319-8b0c-e5c0c03286c5,Inception,,,,148,
+magazine,222111dd-c561-462a-8854-853ada4d3421,National Geographic,,,,,March 2024
+magazine,0afd425b-973f-4af9-a6aa-8febe943a8f6,Time,,,,,"March 15, 2024"
+newspaper,91b74a71-97ad-4fea-b17c-a640c98d355f,The New York Times,,,,,"Morning Edition, March 22, 2024"
+newspaper,45cab344-b792-484c-9156-d929237dde67,The Guardian,,,,,"March 22, 2024"
+book,218b55fa-a3cd-4803-805e-7cd1ef3115ac,The Great Gatsby,978-0743273565,"F. Scott Fitzgerald",180,,
+book,b4249c17-f77b-46da-aa82-7aa227eca5e2,Harry Potter and the Sorcerer's Stone,978-0590353427,"J.K. Rowling",309,,
+dvd,a3cc5ccb-e2fd-4cd0-a6f8-dc1f2f07589b,The Godfather,,,,175,
+dvd,6386364c-8505-4dbe-8731-ff8fa0d6e381,The Dark Knight,,,,152,
+magazine,e5060cc1-33f0-431c-a1b3-d1979e38b6f2,Scientific American,,,,,April 2024
+magazine,7048bd13-49ee-4693-8900-e396bbdf3f98,Vogue,,,,,Spring 2024
+newspaper,6f80a5ce-5958-48f3-a029-ff3d76f2c3fe,The Washington Post,,,,,"Evening Edition, March 22, 2024"
+newspaper,f5f1196c-7935-417e-bc52-7144f63da3cb,The Times,,,,,"March 23, 2024"
+book,faf5a804-e02c-4bbc-8505-4ba90a526e28,Pride and Prejudice,978-0141439518,"Jane Austen",279,,
+book,1aab8182-4345-4ead-98e8-0db53682311b,The Catcher in the Rye,978-0316769488,"J.D. Salinger",277,,
+dvd,2b92ef3d-b224-4589-9a59-cdaba758affd,The Matrix,,,,136,
+dvd,e5d75a1d-f3b4-430f-ba63-b6e4603228eb,Pulp Fiction,,,,154,
+magazine,75fb71ad-ea84-45b8-8396-b790c833573e,Wired,,,,,"May 2024"
+magazine,e30a6739-cdc9-4b2e-ac67-7278fcfb9a59,Forbes,,,,,"April 2024"
+newspaper,3e228c29-6163-477a-8b70-e873a3788758,Los Angeles Times,,,,,"Morning Edition, March 23, 2024"
+newspaper,8e3946e2-d5a6-4cb4-ac92-17cc44935d2d,Chicago Tribune,,,,,"March 23, 2024"
+book,b08c9da7-5c01-494c-84ec-af3fef9dc480,The Lord of the Rings,978-0544003415,"J.R.R. Tolkien",1178,,
+dvd,af1ae237-d29a-49d8-a18a-d6193c07a033,The Silence of the Lambs,,,,118,
+dvd,215af9ba-e881-48fb-8284-a3dc6a1c096d,The Departed,,,,151,
+magazine,8efcbbb2-5c1e-486c-924d-63c3503f498c,The Economist,,,,,"March 23, 2024"
+magazine,d39f5cf3-9574-4fdc-b81b-99d31b26ee92,The New Yorker,,,,,"March 25, 2024"
+newspaper,8b369c0f-6c68-4a84-8e15-8b85a2dd1949,USA Today,,,,,"Morning Edition, March 23, 2024"
+newspaper,eaf356a3-ae28-4cc5-92a2-9b0264165b5d,The Wall Street Journal,,,,,"March 23, 2024"
\ No newline at end of file
diff --git a/lesson_25/db/db_app/src/main/resources/json/data.json b/lesson_25/db/db_app/src/main/resources/json/data.json
new file mode 100644
index 000000000..d419365ff
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/resources/json/data.json
@@ -0,0 +1,268 @@
+{
+    "mediaItems": [
+        {
+            "type": "book",
+            "id": "e27a4e0d-9664-420d-955e-c0e295d0ce02",
+            "title": "To Kill a Mockingbird",
+            "isbn": "978-0061120084",
+            "authors": [
+                "Harper Lee"
+            ],
+            "pages": 336
+        },
+        {
+            "type": "book",
+            "id": "17dd5d20-98f5-4a26-be09-449fea88a3c3",
+            "title": "1984",
+            "isbn": "978-0451524935",
+            "authors": [
+                "George Orwell"
+            ],
+            "pages": 328
+        },
+        {
+            "type": "dvd",
+            "id": "28e5c91f-0e4b-4be5-abb1-8da01fd5587e",
+            "title": "The Shawshank Redemption",
+            "runtime": 142
+        },
+        {
+            "type": "dvd",
+            "id": "295ea581-cd61-4319-8b0c-e5c0c03286c5",
+            "title": "Inception",
+            "runtime": 148
+        },
+        {
+            "type": "magazine",
+            "id": "222111dd-c561-462a-8854-853ada4d3421",
+            "title": "National Geographic",
+            "edition": "March 2024"
+        },
+        {
+            "type": "magazine",
+            "id": "0afd425b-973f-4af9-a6aa-8febe943a8f6",
+            "title": "Time",
+            "edition": "March 15, 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "91b74a71-97ad-4fea-b17c-a640c98d355f",
+            "title": "The New York Times",
+            "edition": "Morning Edition, March 22, 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "45cab344-b792-484c-9156-d929237dde67",
+            "title": "The Guardian",
+            "edition": "March 22, 2024"
+        },
+        {
+            "type": "book",
+            "id": "218b55fa-a3cd-4803-805e-7cd1ef3115ac",
+            "title": "The Great Gatsby",
+            "isbn": "978-0743273565",
+            "authors": [
+                "F. Scott Fitzgerald"
+            ],
+            "pages": 180
+        },
+        {
+            "type": "book",
+            "id": "b4249c17-f77b-46da-aa82-7aa227eca5e2",
+            "title": "Harry Potter and the Sorcerer's Stone",
+            "isbn": "978-0590353427",
+            "authors": [
+                "J.K. Rowling"
+            ],
+            "pages": 309
+        },
+        {
+            "type": "dvd",
+            "id": "a3cc5ccb-e2fd-4cd0-a6f8-dc1f2f07589b",
+            "title": "The Godfather",
+            "runtime": 175
+        },
+        {
+            "type": "dvd",
+            "id": "6386364c-8505-4dbe-8731-ff8fa0d6e381",
+            "title": "The Dark Knight",
+            "runtime": 152
+        },
+        {
+            "type": "magazine",
+            "id": "e5060cc1-33f0-431c-a1b3-d1979e38b6f2",
+            "title": "Scientific American",
+            "edition": "April 2024"
+        },
+        {
+            "type": "magazine",
+            "id": "7048bd13-49ee-4693-8900-e396bbdf3f98",
+            "title": "Vogue",
+            "edition": "Spring 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "6f80a5ce-5958-48f3-a029-ff3d76f2c3fe",
+            "title": "The Washington Post",
+            "edition": "Evening Edition, March 22, 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "f5f1196c-7935-417e-bc52-7144f63da3cb",
+            "title": "The Times",
+            "edition": "March 23, 2024"
+        },
+        {
+            "type": "book",
+            "id": "faf5a804-e02c-4bbc-8505-4ba90a526e28",
+            "title": "Pride and Prejudice",
+            "isbn": "978-0141439518",
+            "authors": [
+                "Jane Austen"
+            ],
+            "pages": 279
+        },
+        {
+            "type": "book",
+            "id": "1aab8182-4345-4ead-98e8-0db53682311b",
+            "title": "The Catcher in the Rye",
+            "isbn": "978-0316769488",
+            "authors": [
+                "J.D. Salinger"
+            ],
+            "pages": 277
+        },
+        {
+            "type": "dvd",
+            "id": "2b92ef3d-b224-4589-9a59-cdaba758affd",
+            "title": "The Matrix",
+            "runtime": 136
+        },
+        {
+            "type": "dvd",
+            "id": "e5d75a1d-f3b4-430f-ba63-b6e4603228eb",
+            "title": "Pulp Fiction",
+            "runtime": 154
+        },
+        {
+            "type": "magazine",
+            "id": "75fb71ad-ea84-45b8-8396-b790c833573e",
+            "title": "Wired",
+            "edition": "May 2024"
+        },
+        {
+            "type": "magazine",
+            "id": "e30a6739-cdc9-4b2e-ac67-7278fcfb9a59",
+            "title": "Forbes",
+            "edition": "April 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "3e228c29-6163-477a-8b70-e873a3788758",
+            "title": "Los Angeles Times",
+            "edition": "Morning Edition, March 23, 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "8e3946e2-d5a6-4cb4-ac92-17cc44935d2d",
+            "title": "Chicago Tribune",
+            "edition": "March 23, 2024"
+        },
+        {
+            "type": "book",
+            "id": "b08c9da7-5c01-494c-84ec-af3fef9dc480",
+            "title": "The Lord of the Rings",
+            "isbn": "978-0544003415",
+            "authors": [
+                "J.R.R. Tolkien"
+            ],
+            "pages": 1178
+        },
+        {
+            "type": "dvd",
+            "id": "af1ae237-d29a-49d8-a18a-d6193c07a033",
+            "title": "The Silence of the Lambs",
+            "runtime": 118
+        },
+        {
+            "type": "dvd",
+            "id": "215af9ba-e881-48fb-8284-a3dc6a1c096d",
+            "title": "The Departed",
+            "runtime": 151
+        },
+        {
+            "type": "magazine",
+            "id": "8efcbbb2-5c1e-486c-924d-63c3503f498c",
+            "title": "The Economist",
+            "edition": "March 23, 2024"
+        },
+        {
+            "type": "magazine",
+            "id": "d39f5cf3-9574-4fdc-b81b-99d31b26ee92",
+            "title": "The New Yorker",
+            "edition": "March 25, 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "8b369c0f-6c68-4a84-8e15-8b85a2dd1949",
+            "title": "USA Today",
+            "edition": "Morning Edition, March 23, 2024"
+        },
+        {
+            "type": "newspaper",
+            "id": "eaf356a3-ae28-4cc5-92a2-9b0264165b5d",
+            "title": "The Wall Street Journal",
+            "edition": "March 23, 2024"
+        }
+    ],
+    "guests": [
+        {
+            "type": "librarian",
+            "name": "John Doe",
+            "email": "john.doe@fakelibrary.org",
+            "checkedOutItems": []
+        },
+        {
+            "type": "patron",
+            "name": "Jane Smith",
+            "email": "jane.smith@example.com",
+            "checkedOutItems": [
+                {
+                    "itemId": "e27a4e0d-9664-420d-955e-c0e295d0ce02",
+                    "dueDate": "2024-04-05T00:00:00Z" 
+                },
+                {
+                    "itemId": "295ea581-cd61-4319-8b0c-e5c0c03286c5",
+                    "dueDate": "2024-04-07T00:00:00Z" 
+                }
+            ]
+        },
+        {
+            "type": "patron",
+            "name": "Alice Johnson",
+            "email": "alice.johnson@example.com",
+            "checkedOutItems": [
+                {
+                    "itemId": "17dd5d20-98f5-4a26-be09-449fea88a3c3",
+                    "dueDate": "2024-04-03T00:00:00Z" 
+                },
+                {
+                    "itemId": "28e5c91f-0e4b-4be5-abb1-8da01fd5587e",
+                    "dueDate": "2024-04-06T00:00:00Z" 
+                }
+            ]
+        },
+        {
+            "type": "librarian",
+            "name": "Bob Williams",
+            "email": "bob.williams@fakelibrary.org",
+            "checkedOutItems": []
+        },
+        {
+            "type": "patron",
+            "name": "Emily Brown",
+            "email": "emily.brown@example.com",
+            "checkedOutItems": []
+        }
+    ]
+}
\ No newline at end of file
diff --git a/lesson_25/db/db_app/src/main/resources/queries/anthonydmays.sql b/lesson_25/db/db_app/src/main/resources/queries/anthonydmays.sql
new file mode 100644
index 000000000..027b7d63f
--- /dev/null
+++ b/lesson_25/db/db_app/src/main/resources/queries/anthonydmays.sql
@@ -0,0 +1 @@
+SELECT 1;
\ No newline at end of file
diff --git a/lesson_25/db/db_app/src/main/resources/sqlite/data.db b/lesson_25/db/db_app/src/main/resources/sqlite/data.db
new file mode 100644
index 000000000..8baa982d2
Binary files /dev/null and b/lesson_25/db/db_app/src/main/resources/sqlite/data.db differ
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/Lesson25Test.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/Lesson25Test.java
new file mode 100644
index 000000000..e29867d7f
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/Lesson25Test.java
@@ -0,0 +1,13 @@
+package com.codedifferently.lesson25;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class Lesson25Test {
+
+  @Test
+  void testInstantiate() {
+    assertThat(new Lesson25()).isNotNull();
+  }
+}
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/factory/LibraryCsvDataLoaderTest.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/factory/LibraryCsvDataLoaderTest.java
new file mode 100644
index 000000000..b5119cd7d
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/factory/LibraryCsvDataLoaderTest.java
@@ -0,0 +1,84 @@
+package com.codedifferently.lesson25.factory;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.codedifferently.lesson25.Lesson25;
+import com.codedifferently.lesson25.library.LibraryGuest;
+import com.codedifferently.lesson25.library.MediaItem;
+import com.codedifferently.lesson25.models.CheckoutModel;
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.TestInstance;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.ContextConfiguration;
+
+@SpringBootTest
+@TestInstance(TestInstance.Lifecycle.PER_CLASS)
+@ContextConfiguration(classes = Lesson25.class)
+class LibraryCsvDataLoaderTest {
+
+  private LibraryDataModel libraryDataModel;
+
+  @BeforeAll
+  void beforeAll() throws Exception {
+    libraryDataModel = new LibraryCsvDataLoader().loadData();
+  }
+
+  @Test
+  void testDataLoader_loadsCheckedOutItems() {
+    Map<String, List<CheckoutModel>> checkedOutItemsByGuest =
+        libraryDataModel.getCheckoutsByEmail();
+    var numCheckedOutItems = checkedOutItemsByGuest.values().stream().mapToInt(List::size).sum();
+    assertThat(numCheckedOutItems)
+        .describedAs("LibraryCsvDataLoader should load checked out items")
+        .isEqualTo(4);
+  }
+
+  @Test
+  void testDataLoader_loadsCorrectItemTypes() {
+    List<MediaItem> items = libraryDataModel.getMediaItems();
+    Map<String, Integer> countByMediaType =
+        items.stream()
+            .reduce(
+                new HashMap<>(),
+                (hashMap, e) -> {
+                  hashMap.merge(e.getType(), 1, Integer::sum);
+                  return hashMap;
+                },
+                (m, m2) -> {
+                  m.putAll(m2);
+                  return m;
+                });
+    assertThat(countByMediaType.get("book")).isEqualTo(7);
+    assertThat(countByMediaType.get("magazine")).isEqualTo(8);
+    assertThat(countByMediaType.get("newspaper")).isEqualTo(8);
+    assertThat(countByMediaType.get("dvd")).isEqualTo(8);
+    assertThat(items.stream().map(MediaItem::getId).distinct().count()).isEqualTo(31);
+    assertThat(items.stream().map(MediaItem::getTitle).distinct().count()).isEqualTo(31);
+  }
+
+  @Test
+  void testDataLoader_loadsCorrectGuestTypes() {
+    List<LibraryGuest> guests = libraryDataModel.getGuests();
+    Map<String, Integer> countByGuestType =
+        guests.stream()
+            .reduce(
+                new HashMap<>(),
+                (hashMap, e) -> {
+                  hashMap.merge(e.getClass().getSimpleName(), 1, Integer::sum);
+                  return hashMap;
+                },
+                (m, m2) -> {
+                  m.putAll(m2);
+                  return m;
+                });
+    assertThat(countByGuestType.get("Librarian")).isEqualTo(2);
+    assertThat(countByGuestType.get("Patron")).isEqualTo(3);
+    assertThat(guests.stream().map(LibraryGuest::getEmail).distinct().count()).isEqualTo(5);
+    assertThat(guests.stream().map(LibraryGuest::getName).distinct().count()).isEqualTo(5);
+  }
+}
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/factory/LibraryJsonDataLoaderTest.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/factory/LibraryJsonDataLoaderTest.java
new file mode 100644
index 000000000..4b8cb8dd0
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/factory/LibraryJsonDataLoaderTest.java
@@ -0,0 +1,76 @@
+package com.codedifferently.lesson25.factory;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import com.codedifferently.lesson25.library.LibraryGuest;
+import com.codedifferently.lesson25.library.MediaItem;
+import com.codedifferently.lesson25.models.CheckoutModel;
+import com.codedifferently.lesson25.models.LibraryDataModel;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+class LibraryJsonDataLoaderTest {
+
+  private static LibraryDataModel libraryDataModel;
+
+  @BeforeAll
+  static void beforeAll() throws Exception {
+    var libraryJsonDataLoader = new LibraryJsonDataLoader();
+    libraryDataModel = libraryJsonDataLoader.loadData();
+  }
+
+  @Test
+  void testDataLoader_loadsCheckedOutItems() {
+    Map<String, List<CheckoutModel>> checkedOutItemsByGuest =
+        libraryDataModel.getCheckoutsByEmail();
+    var numCheckedOutItems = checkedOutItemsByGuest.values().stream().mapToInt(List::size).sum();
+    assertThat(numCheckedOutItems).isEqualTo(4);
+  }
+
+  @Test
+  void testDataLoader_loadsCorrectItemTypes() {
+    List<MediaItem> items = libraryDataModel.getMediaItems();
+    Map<String, Integer> countByMediaType =
+        items.stream()
+            .reduce(
+                new HashMap<>(),
+                (hashMap, e) -> {
+                  hashMap.merge(e.getType(), 1, Integer::sum);
+                  return hashMap;
+                },
+                (m, m2) -> {
+                  m.putAll(m2);
+                  return m;
+                });
+    assertThat(countByMediaType.get("book")).isEqualTo(7);
+    assertThat(countByMediaType.get("magazine")).isEqualTo(8);
+    assertThat(countByMediaType.get("newspaper")).isEqualTo(8);
+    assertThat(countByMediaType.get("dvd")).isEqualTo(8);
+    assertThat(items.stream().map(MediaItem::getId).distinct().count()).isEqualTo(31);
+    assertThat(items.stream().map(MediaItem::getTitle).distinct().count()).isEqualTo(31);
+  }
+
+  @Test
+  void testDataLoader_loadsCorrectGuestTypes() {
+    List<LibraryGuest> guests = libraryDataModel.getGuests();
+    Map<String, Integer> countByGuestType =
+        guests.stream()
+            .reduce(
+                new HashMap<>(),
+                (hashMap, e) -> {
+                  hashMap.merge(e.getClass().getSimpleName(), 1, Integer::sum);
+                  return hashMap;
+                },
+                (m, m2) -> {
+                  m.putAll(m2);
+                  return m;
+                });
+    assertThat(countByGuestType.get("Librarian")).isEqualTo(2);
+    assertThat(countByGuestType.get("Patron")).isEqualTo(3);
+    assertThat(guests.stream().map(LibraryGuest::getEmail).distinct().count()).isEqualTo(5);
+    assertThat(guests.stream().map(LibraryGuest::getName).distinct().count()).isEqualTo(5);
+  }
+}
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/BookTest.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/BookTest.java
new file mode 100644
index 000000000..024c0f7e3
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/BookTest.java
@@ -0,0 +1,94 @@
+package com.codedifferently.lesson25.library;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import java.util.List;
+import java.util.UUID;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class BookTest {
+
+  private Book classUnderTest;
+  private Library library;
+
+  @BeforeEach
+  void setUp() {
+    classUnderTest =
+        new Book(
+            UUID.fromString("2b7591dd-f418-4115-974e-45115b3bf39a"),
+            "To Kill a Mockingbird",
+            "978-0061120084",
+            List.of("Harper Lee"),
+            281);
+    library = mock(Library.class);
+    when(library.getId()).thenReturn("Library 1");
+    when(library.hasMediaItem(classUnderTest)).thenReturn(true);
+    classUnderTest.setLibrary(library);
+  }
+
+  @Test
+  void testPatron_created() {
+    // Assert
+    assertThat(classUnderTest.getTitle()).isEqualTo("To Kill a Mockingbird");
+    assertThat(classUnderTest.getIsbn()).isEqualTo("978-0061120084");
+    assertThat(classUnderTest.getAuthors()).isEqualTo(List.of("Harper Lee"));
+    assertThat(classUnderTest.getNumberOfPages()).isEqualTo(281);
+  }
+
+  @Test
+  void testSetLibrary_WrongLibrary() {
+    // Arrange
+    Library otherLibrary = mock(Library.class);
+    when(otherLibrary.hasMediaItem(classUnderTest)).thenReturn(false);
+    when(otherLibrary.getId()).thenReturn("Library 2");
+
+    // Act & Assert
+    assertThatThrownBy(() -> classUnderTest.setLibrary(otherLibrary))
+        .isInstanceOf(WrongLibraryException.class)
+        .hasMessageContaining(
+            "Media item 2b7591dd-f418-4115-974e-45115b3bf39a is not in library Library 2");
+  }
+
+  @Test
+  void testIsCheckedOut_LibraryNotSet() {
+    // Arrange
+    classUnderTest.setLibrary(null);
+
+    // Act & Assert
+    assertThatThrownBy(() -> classUnderTest.isCheckedOut())
+        .isInstanceOf(LibraryNotSetException.class)
+        .hasMessageContaining("Library not set for item 2b7591dd-f418-4115-974e-45115b3bf39a");
+  }
+
+  @Test
+  void testIsCheckedOut() {
+    // Arrange
+    when(library.isCheckedOut(classUnderTest)).thenReturn(true);
+
+    // Act & Assert
+    assertThat(classUnderTest.isCheckedOut()).isTrue();
+  }
+
+  @Test
+  void testIsCheckedOut_whenNotCheckedOut() {
+    // Arrange
+    when(library.isCheckedOut(classUnderTest)).thenReturn(false);
+
+    // Act & Assert
+    assertThat(classUnderTest.isCheckedOut()).isFalse();
+  }
+
+  @Test
+  void testToString() {
+    // Act & Assert
+    assertThat(classUnderTest.toString())
+        .isEqualTo(
+            "Book{id='2b7591dd-f418-4115-974e-45115b3bf39a', title='To Kill a Mockingbird'}");
+  }
+}
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/LibraryTest.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/LibraryTest.java
new file mode 100644
index 000000000..3fbef4af8
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/LibraryTest.java
@@ -0,0 +1,338 @@
+package com.codedifferently.lesson25.library;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.codedifferently.lesson25.library.exceptions.MediaItemCheckedOutException;
+import java.util.List;
+import java.util.UUID;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class LibraryTest {
+
+  private Library classUnderTest;
+
+  @BeforeEach
+  void setUp() {
+    classUnderTest = new Library("compton-library");
+  }
+
+  @Test
+  void testLibrary_canAddItems() {
+    // Arrange
+    Book book1 =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Book book2 =
+        new Book(
+            UUID.randomUUID(),
+            "To Kill a Mockingbird",
+            "978-0061120084",
+            List.of("Harper Lee"),
+            281);
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    // Act
+    classUnderTest.addMediaItem(book1, librarian);
+    classUnderTest.addMediaItem(book2, librarian);
+    // Assert
+    assertThat(classUnderTest.hasMediaItem(book1)).isTrue();
+    assertThat(classUnderTest.hasMediaItem(book2)).isTrue();
+  }
+
+  @Test
+  void testLibrary_canRemoveItems() {
+    // Arrange
+    Book book1 =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Book book2 =
+        new Book(
+            UUID.randomUUID(),
+            "To Kill a Mockingbird",
+            "978-0061120084",
+            List.of("Harper Lee"),
+            281);
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(book1, librarian);
+    classUnderTest.addMediaItem(book2, librarian);
+    // Act
+    classUnderTest.removeMediaItem(book1, librarian);
+    classUnderTest.removeMediaItem(book2, librarian);
+    // Assert
+    assertThat(classUnderTest.hasMediaItem(book1)).isFalse();
+    assertThat(classUnderTest.hasMediaItem(book2)).isFalse();
+  }
+
+  @Test
+  void testLibrary_canAddPatrons() {
+    // Arrange
+    Patron patron1 = new Patron("John Doe", "john@example.com");
+    Patron patron2 = new Patron("Jane Doe", "jane@example.com");
+    // Act
+    classUnderTest.addLibraryGuest(patron1);
+    classUnderTest.addLibraryGuest(patron2);
+    // Assert
+    assertThat(classUnderTest.hasLibraryGuest(patron1)).isTrue();
+    assertThat(classUnderTest.hasLibraryGuest(patron2)).isTrue();
+  }
+
+  @Test
+  void testLibrary_canRemovePatrons() {
+    // Arrange
+    Patron patron1 = new Patron("John Doe", "john@example.com");
+    Patron patron2 = new Patron("Jane Doe", "jane@example.com");
+    classUnderTest.addLibraryGuest(patron1);
+    classUnderTest.addLibraryGuest(patron2);
+    // Act
+    classUnderTest.removeLibraryGuest(patron1);
+    classUnderTest.removeLibraryGuest(patron2);
+    // Assert
+    assertThat(classUnderTest.hasLibraryGuest(patron1)).isFalse();
+    assertThat(classUnderTest.hasLibraryGuest(patron2)).isFalse();
+  }
+
+  @Test
+  void testLibrary_allowsPatronToCheckoutBook() {
+    // Arrange
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(patron);
+    // Act
+    boolean wasCheckedOut = classUnderTest.checkOutMediaItem(book, patron);
+    // Assert
+    assertThat(wasCheckedOut).isTrue();
+    assertThat(classUnderTest.isCheckedOut(book)).isTrue();
+    assertThat(patron.getCheckedOutMediaItems().contains(book)).isTrue();
+  }
+
+  @Test
+  void testLibrary_allowPatronToCheckInBook() {
+    // Arrange
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(patron);
+    classUnderTest.checkOutMediaItem(book, patron);
+    // Act
+    boolean wasReturned = classUnderTest.checkInMediaItem(book, patron);
+    // Assert
+    assertThat(wasReturned).isTrue();
+    assertThat(classUnderTest.isCheckedOut(book)).isFalse();
+    assertThat(patron.getCheckedOutMediaItems().contains(book)).isFalse();
+  }
+
+  @Test
+  void testLibrary_allowLibrarianToCheckOutBook() {
+    // Arrange
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(librarian);
+    // Act
+    boolean wasCheckedOut = classUnderTest.checkOutMediaItem(book, librarian);
+    // Assert
+    assertThat(wasCheckedOut).isTrue();
+    assertThat(librarian.getCheckedOutMediaItems().contains(book)).isTrue();
+  }
+
+  @Test
+  void testLibrary_allowLibrarianToCheckInBook() {
+    // Arrange
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Librarian librarian = new Librarian("John Doe", "john@example.com");
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(librarian);
+    classUnderTest.checkOutMediaItem(book, librarian);
+    // Act
+    boolean wasReturned = classUnderTest.checkInMediaItem(book, librarian);
+    // Assert
+    assertThat(wasReturned).isTrue();
+    assertThat(classUnderTest.isCheckedOut(book)).isFalse();
+    assertThat(librarian.getCheckedOutMediaItems().contains(book)).isFalse();
+  }
+
+  @Test
+  void testLibrary_preventsMultipleCheckouts() {
+    // Arrange
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(patron);
+    classUnderTest.checkOutMediaItem(book, patron);
+    // Act
+    boolean wasCheckedOut = classUnderTest.checkOutMediaItem(book, patron);
+    // Assert
+    assertThat(wasCheckedOut).isFalse();
+    assertThat(classUnderTest.isCheckedOut(book)).isTrue();
+  }
+
+  @Test
+  void testLibrary_preventsRemovingPatronWithCheckedOutItems() {
+    // Arrange
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(patron);
+    classUnderTest.checkOutMediaItem(book, patron);
+    // Act
+    assertThatThrownBy(() -> classUnderTest.removeLibraryGuest(patron))
+        .isInstanceOf(MediaItemCheckedOutException.class)
+        .hasMessage("Cannot remove guest with checked out items.");
+  }
+
+  @Test
+  void testLibrary_preventsRemovingCheckedOutItems() {
+    // Arrange
+    Book book =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Patron patron = new Patron("Jane Doe", "jane@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(book, librarian);
+    classUnderTest.addLibraryGuest(patron);
+    classUnderTest.checkOutMediaItem(book, patron);
+    // Act
+    assertThatThrownBy(() -> classUnderTest.removeMediaItem(book, librarian))
+        .isInstanceOf(MediaItemCheckedOutException.class)
+        .hasMessage("Cannot remove checked out item.");
+  }
+
+  @Test
+  void testLibrary_canAddDvd() {
+    // Arrange
+    Dvd dvd = new Dvd(UUID.randomUUID(), "The Great Gatsby");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    // Act
+    classUnderTest.addMediaItem(dvd, librarian);
+    // Assert
+    assertThat(classUnderTest.hasMediaItem(dvd)).isTrue();
+  }
+
+  @Test
+  void testLibrary_canRemoveDvd() {
+    // Arrange
+    Dvd dvd = new Dvd(UUID.randomUUID(), "The Great Gatsby");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    // Act
+    classUnderTest.removeMediaItem(dvd, librarian);
+    // Assert
+    assertThat(classUnderTest.hasMediaItem(dvd)).isFalse();
+  }
+
+  @Test
+  void testLibrary_allowLibrarianToCheckOutDvd() {
+    // Arrange
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    Dvd dvd = new Dvd(UUID.randomUUID(), "The Great Gatsby");
+    classUnderTest.addMediaItem(dvd, librarian);
+    classUnderTest.addLibraryGuest(librarian);
+    // Act
+    boolean wasCheckedOut = classUnderTest.checkOutMediaItem(dvd, librarian);
+    // Assert
+    assertThat(wasCheckedOut).isTrue();
+    assertThat(librarian.getCheckedOutMediaItems().contains(dvd)).isTrue();
+  }
+
+  @Test
+  void testLibrary_allowPatronToCheckInDvd() {
+    // Arrange
+    Dvd dvd = new Dvd(UUID.randomUUID(), "The Great Gatsby");
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    classUnderTest.addMediaItem(dvd, librarian);
+    classUnderTest.addLibraryGuest(patron);
+    classUnderTest.checkOutMediaItem(dvd, patron);
+    // Act
+    boolean wasReturned = classUnderTest.checkInMediaItem(dvd, patron);
+    // Assert
+    assertThat(wasReturned).isTrue();
+    assertThat(classUnderTest.isCheckedOut(dvd)).isFalse();
+    assertThat(patron.getCheckedOutMediaItems().contains(dvd)).isFalse();
+  }
+
+  @Test
+  void testLibrary_preventsGuestFromCheckingOutMagazine() {
+    // Arrange
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    Magazine magazine = new Magazine(UUID.randomUUID(), "The Great Gatsby");
+    classUnderTest.addMediaItem(magazine, librarian);
+    classUnderTest.addLibraryGuest(librarian);
+    classUnderTest.addLibraryGuest(patron);
+    // Act
+    boolean wasCheckedOut = classUnderTest.checkOutMediaItem(magazine, librarian);
+    // Assert
+    assertThat(wasCheckedOut).isFalse();
+    assertThat(patron.getCheckedOutMediaItems().contains(magazine)).isFalse();
+  }
+
+  @Test
+  void testLibrary_preventsGuestFromCheckingOutNewspaper() {
+    // Arrange
+    Patron patron = new Patron("John Doe", "john@example.com");
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    Newspaper newspaper = new Newspaper(UUID.randomUUID(), "LA Times");
+    classUnderTest.addMediaItem(newspaper, librarian);
+    classUnderTest.addLibraryGuest(librarian);
+    classUnderTest.addLibraryGuest(patron);
+    // Act
+    boolean wasCheckedOut = classUnderTest.checkOutMediaItem(newspaper, librarian);
+    // Assert
+    assertThat(wasCheckedOut).isFalse();
+    assertThat(patron.getCheckedOutMediaItems().contains(newspaper)).isFalse();
+  }
+}
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/MediaItemBaseTest.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/MediaItemBaseTest.java
new file mode 100644
index 000000000..9387a9a44
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/MediaItemBaseTest.java
@@ -0,0 +1,96 @@
+package com.codedifferently.lesson25.library;
+
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import java.util.UUID;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class MediaItemBaseTest {
+
+  private MediaItemBase mediaItem;
+  private static final UUID ITEM_ID = UUID.fromString("af71ac38-7628-415f-a2cd-bcaf7e001b97");
+
+  class MockMediaItem extends MediaItemBase {
+
+    public MockMediaItem(UUID id, String title) {
+      super(id, title);
+    }
+
+    @Override
+    public String getType() {
+      return "mock";
+    }
+  }
+
+  @BeforeEach
+  void setUp() {
+    mediaItem = new MockMediaItem(ITEM_ID, "Sample Title");
+  }
+
+  @Test
+  void getId() {
+    assertEquals(ITEM_ID, mediaItem.getId());
+  }
+
+  @Test
+  void getTitle() {
+    assertEquals("Sample Title", mediaItem.getTitle());
+  }
+
+  @Test
+  void setLibrary_withWrongLibraryException() {
+    Library library = mock(Library.class);
+    when(library.getId()).thenReturn("compton-library");
+    when(library.hasMediaItem(mediaItem)).thenReturn(false);
+    assertThatThrownBy(() -> mediaItem.setLibrary(library))
+        .isInstanceOf(WrongLibraryException.class)
+        .hasMessage(
+            "Media item af71ac38-7628-415f-a2cd-bcaf7e001b97 is not in library compton-library");
+  }
+
+  @Test
+  void isCheckedOut() throws LibraryNotSetException {
+    Library library = mock(Library.class);
+    when(library.hasMediaItem(mediaItem)).thenReturn(true);
+    when(library.isCheckedOut(mediaItem)).thenReturn(true);
+    mediaItem.setLibrary(library);
+    assertTrue(mediaItem.isCheckedOut());
+  }
+
+  @Test
+  void isCheckedOut_withLibraryNotSetException() {
+    assertThatThrownBy(() -> mediaItem.isCheckedOut())
+        .isInstanceOf(LibraryNotSetException.class)
+        .hasMessage("Library not set for item af71ac38-7628-415f-a2cd-bcaf7e001b97");
+  }
+
+  @Test
+  void canCheckOut() {
+    assertTrue(mediaItem.canCheckOut());
+  }
+
+  @Test
+  void equals() {
+    MediaItemBase mediaItem2 = new MockMediaItem(ITEM_ID, "Sample Title");
+    assertEquals(mediaItem, mediaItem2);
+  }
+
+  @Test
+  void hashCodeTest() {
+    MediaItemBase mediaItem2 = new MockMediaItem(ITEM_ID, "Sample Title");
+    assertEquals(mediaItem.hashCode(), mediaItem2.hashCode());
+  }
+
+  @Test
+  void toStringTest() {
+    String expected = "MediaItem{id='af71ac38-7628-415f-a2cd-bcaf7e001b97', title='Sample Title'}";
+    assertEquals(expected, mediaItem.toString());
+  }
+}
diff --git a/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/PatronTest.java b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/PatronTest.java
new file mode 100644
index 000000000..69aab997e
--- /dev/null
+++ b/lesson_25/db/db_app/src/test/java/com/codedifferently/lesson25/library/PatronTest.java
@@ -0,0 +1,93 @@
+package com.codedifferently.lesson25.library;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import com.codedifferently.lesson25.library.exceptions.LibraryNotSetException;
+import com.codedifferently.lesson25.library.exceptions.WrongLibraryException;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.UUID;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+class PatronTest {
+
+  private Patron classUnderTest;
+  private Library library;
+
+  @BeforeEach
+  void setUp() {
+    classUnderTest = new Patron("John Doe", "johndoe@example.com");
+    library = new Library("Library 1");
+    library.addLibraryGuest(classUnderTest);
+  }
+
+  @Test
+  void testPatron_created() {
+    // Assert
+    assertThat(classUnderTest.getName()).isEqualTo("John Doe");
+    assertThat(classUnderTest.getId()).isEqualTo("johndoe@example.com");
+  }
+
+  @Test
+  void testSetLibrary_WrongLibrary() {
+    // Arrange
+    Library otherLibrary = new Library("Library 2");
+
+    // Act & Assert
+    assertThatThrownBy(() -> classUnderTest.setLibrary(otherLibrary))
+        .isInstanceOf(WrongLibraryException.class)
+        .hasMessageContaining("Patron johndoe@example.com is not in library Library 2");
+  }
+
+  @Test
+  void testGetCheckedOutBooks_LibraryNotSet() {
+    // Arrange
+    classUnderTest.setLibrary(null);
+
+    // Act & Assert
+    assertThatThrownBy(() -> classUnderTest.getCheckedOutMediaItems())
+        .isInstanceOf(LibraryNotSetException.class)
+        .hasMessageContaining("Library not set for patron johndoe@example.com");
+  }
+
+  @Test
+  void testGetCheckedOutBooks() {
+    // Arrange
+    Book book1 =
+        new Book(
+            UUID.randomUUID(),
+            "The Great Gatsby",
+            "978-0743273565",
+            List.of("F. Scott Fitzgerald"),
+            180);
+    Book book2 =
+        new Book(
+            UUID.randomUUID(),
+            "To Kill a Mockingbird",
+            "978-0061120084",
+            List.of("Harper Lee"),
+            281);
+    Librarian librarian = new Librarian("Anthony Mays", "anthony@example.com");
+    Set<Book> expectedBooks = new HashSet<>();
+    expectedBooks.add(book1);
+    expectedBooks.add(book2);
+
+    library.addMediaItem(book1, librarian);
+    library.addMediaItem(book2, librarian);
+    library.checkOutMediaItem(book1, classUnderTest);
+    library.checkOutMediaItem(book2, classUnderTest);
+
+    // Act & Assert
+    assertThat(classUnderTest.getCheckedOutMediaItems()).isEqualTo(expectedBooks);
+  }
+
+  @Test
+  void testToString() {
+    // Act & Assert
+    assertThat(classUnderTest.toString())
+        .isEqualTo("Patron{id='johndoe@example.com', name='John Doe'}");
+  }
+}
diff --git a/lesson_25/db/gradle/wrapper/gradle-wrapper.jar b/lesson_25/db/gradle/wrapper/gradle-wrapper.jar
new file mode 100644
index 000000000..a4b76b953
Binary files /dev/null and b/lesson_25/db/gradle/wrapper/gradle-wrapper.jar differ
diff --git a/lesson_25/db/gradle/wrapper/gradle-wrapper.properties b/lesson_25/db/gradle/wrapper/gradle-wrapper.properties
new file mode 100644
index 000000000..e2847c820
--- /dev/null
+++ b/lesson_25/db/gradle/wrapper/gradle-wrapper.properties
@@ -0,0 +1,7 @@
+distributionBase=GRADLE_USER_HOME
+distributionPath=wrapper/dists
+distributionUrl=https\://services.gradle.org/distributions/gradle-8.11.1-bin.zip
+networkTimeout=10000
+validateDistributionUrl=true
+zipStoreBase=GRADLE_USER_HOME
+zipStorePath=wrapper/dists
diff --git a/lesson_25/db/gradlew b/lesson_25/db/gradlew
new file mode 100755
index 000000000..f5feea6d6
--- /dev/null
+++ b/lesson_25/db/gradlew
@@ -0,0 +1,252 @@
+#!/bin/sh
+
+#
+# Copyright © 2015-2021 the original authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+# SPDX-License-Identifier: Apache-2.0
+#
+
+##############################################################################
+#
+#   Gradle start up script for POSIX generated by Gradle.
+#
+#   Important for running:
+#
+#   (1) You need a POSIX-compliant shell to run this script. If your /bin/sh is
+#       noncompliant, but you have some other compliant shell such as ksh or
+#       bash, then to run this script, type that shell name before the whole
+#       command line, like:
+#
+#           ksh Gradle
+#
+#       Busybox and similar reduced shells will NOT work, because this script
+#       requires all of these POSIX shell features:
+#         * functions;
+#         * expansions «$var», «${var}», «${var:-default}», «${var+SET}»,
+#           «${var#prefix}», «${var%suffix}», and «$( cmd )»;
+#         * compound commands having a testable exit status, especially «case»;
+#         * various built-in commands including «command», «set», and «ulimit».
+#
+#   Important for patching:
+#
+#   (2) This script targets any POSIX shell, so it avoids extensions provided
+#       by Bash, Ksh, etc; in particular arrays are avoided.
+#
+#       The "traditional" practice of packing multiple parameters into a
+#       space-separated string is a well documented source of bugs and security
+#       problems, so this is (mostly) avoided, by progressively accumulating
+#       options in "$@", and eventually passing that to Java.
+#
+#       Where the inherited environment variables (DEFAULT_JVM_OPTS, JAVA_OPTS,
+#       and GRADLE_OPTS) rely on word-splitting, this is performed explicitly;
+#       see the in-line comments for details.
+#
+#       There are tweaks for specific operating systems such as AIX, CygWin,
+#       Darwin, MinGW, and NonStop.
+#
+#   (3) This script is generated from the Groovy template
+#       https://github.com/gradle/gradle/blob/HEAD/platforms/jvm/plugins-application/src/main/resources/org/gradle/api/internal/plugins/unixStartScript.txt
+#       within the Gradle project.
+#
+#       You can find Gradle at https://github.com/gradle/gradle/.
+#
+##############################################################################
+
+# Attempt to set APP_HOME
+
+# Resolve links: $0 may be a link
+app_path=$0
+
+# Need this for daisy-chained symlinks.
+while
+    APP_HOME=${app_path%"${app_path##*/}"}  # leaves a trailing /; empty if no leading path
+    [ -h "$app_path" ]
+do
+    ls=$( ls -ld "$app_path" )
+    link=${ls#*' -> '}
+    case $link in             #(
+      /*)   app_path=$link ;; #(
+      *)    app_path=$APP_HOME$link ;;
+    esac
+done
+
+# This is normally unused
+# shellcheck disable=SC2034
+APP_BASE_NAME=${0##*/}
+# Discard cd standard output in case $CDPATH is set (https://github.com/gradle/gradle/issues/25036)
+APP_HOME=$( cd -P "${APP_HOME:-./}" > /dev/null && printf '%s
+' "$PWD" ) || exit
+
+# Use the maximum available, or set MAX_FD != -1 to use that value.
+MAX_FD=maximum
+
+warn () {
+    echo "$*"
+} >&2
+
+die () {
+    echo
+    echo "$*"
+    echo
+    exit 1
+} >&2
+
+# OS specific support (must be 'true' or 'false').
+cygwin=false
+msys=false
+darwin=false
+nonstop=false
+case "$( uname )" in                #(
+  CYGWIN* )         cygwin=true  ;; #(
+  Darwin* )         darwin=true  ;; #(
+  MSYS* | MINGW* )  msys=true    ;; #(
+  NONSTOP* )        nonstop=true ;;
+esac
+
+CLASSPATH=$APP_HOME/gradle/wrapper/gradle-wrapper.jar
+
+
+# Determine the Java command to use to start the JVM.
+if [ -n "$JAVA_HOME" ] ; then
+    if [ -x "$JAVA_HOME/jre/sh/java" ] ; then
+        # IBM's JDK on AIX uses strange locations for the executables
+        JAVACMD=$JAVA_HOME/jre/sh/java
+    else
+        JAVACMD=$JAVA_HOME/bin/java
+    fi
+    if [ ! -x "$JAVACMD" ] ; then
+        die "ERROR: JAVA_HOME is set to an invalid directory: $JAVA_HOME
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+else
+    JAVACMD=java
+    if ! command -v java >/dev/null 2>&1
+    then
+        die "ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH.
+
+Please set the JAVA_HOME variable in your environment to match the
+location of your Java installation."
+    fi
+fi
+
+# Increase the maximum file descriptors if we can.
+if ! "$cygwin" && ! "$darwin" && ! "$nonstop" ; then
+    case $MAX_FD in #(
+      max*)
+        # In POSIX sh, ulimit -H is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        MAX_FD=$( ulimit -H -n ) ||
+            warn "Could not query maximum file descriptor limit"
+    esac
+    case $MAX_FD in  #(
+      '' | soft) :;; #(
+      *)
+        # In POSIX sh, ulimit -n is undefined. That's why the result is checked to see if it worked.
+        # shellcheck disable=SC2039,SC3045
+        ulimit -n "$MAX_FD" ||
+            warn "Could not set maximum file descriptor limit to $MAX_FD"
+    esac
+fi
+
+# Collect all arguments for the java command, stacking in reverse order:
+#   * args from the command line
+#   * the main class name
+#   * -classpath
+#   * -D...appname settings
+#   * --module-path (only if needed)
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, and GRADLE_OPTS environment variables.
+
+# For Cygwin or MSYS, switch paths to Windows format before running java
+if "$cygwin" || "$msys" ; then
+    APP_HOME=$( cygpath --path --mixed "$APP_HOME" )
+    CLASSPATH=$( cygpath --path --mixed "$CLASSPATH" )
+
+    JAVACMD=$( cygpath --unix "$JAVACMD" )
+
+    # Now convert the arguments - kludge to limit ourselves to /bin/sh
+    for arg do
+        if
+            case $arg in                                #(
+              -*)   false ;;                            # don't mess with options #(
+              /?*)  t=${arg#/} t=/${t%%/*}              # looks like a POSIX filepath
+                    [ -e "$t" ] ;;                      #(
+              *)    false ;;
+            esac
+        then
+            arg=$( cygpath --path --ignore --mixed "$arg" )
+        fi
+        # Roll the args list around exactly as many times as the number of
+        # args, so each arg winds up back in the position where it started, but
+        # possibly modified.
+        #
+        # NB: a `for` loop captures its iteration list before it begins, so
+        # changing the positional parameters here affects neither the number of
+        # iterations, nor the values presented in `arg`.
+        shift                   # remove old arg
+        set -- "$@" "$arg"      # push replacement arg
+    done
+fi
+
+
+# Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+DEFAULT_JVM_OPTS='"-Xmx64m" "-Xms64m"'
+
+# Collect all arguments for the java command:
+#   * DEFAULT_JVM_OPTS, JAVA_OPTS, JAVA_OPTS, and optsEnvironmentVar are not allowed to contain shell fragments,
+#     and any embedded shellness will be escaped.
+#   * For example: A user cannot expect ${Hostname} to be expanded, as it is an environment variable and will be
+#     treated as '${Hostname}' itself on the command line.
+
+set -- \
+        "-Dorg.gradle.appname=$APP_BASE_NAME" \
+        -classpath "$CLASSPATH" \
+        org.gradle.wrapper.GradleWrapperMain \
+        "$@"
+
+# Stop when "xargs" is not available.
+if ! command -v xargs >/dev/null 2>&1
+then
+    die "xargs is not available"
+fi
+
+# Use "xargs" to parse quoted args.
+#
+# With -n1 it outputs one arg per line, with the quotes and backslashes removed.
+#
+# In Bash we could simply go:
+#
+#   readarray ARGS < <( xargs -n1 <<<"$var" ) &&
+#   set -- "${ARGS[@]}" "$@"
+#
+# but POSIX shell has neither arrays nor command substitution, so instead we
+# post-process each arg (as a line of input to sed) to backslash-escape any
+# character that might be a shell metacharacter, then use eval to reverse
+# that process (while maintaining the separation between arguments), and wrap
+# the whole thing up as a single "set" statement.
+#
+# This will of course break if any of these variables contains a newline or
+# an unmatched quote.
+#
+
+eval "set -- $(
+        printf '%s\n' "$DEFAULT_JVM_OPTS $JAVA_OPTS $GRADLE_OPTS" |
+        xargs -n1 |
+        sed ' s~[^-[:alnum:]+,./:=@_]~\\&~g; ' |
+        tr '\n' ' '
+    )" '"$@"'
+
+exec "$JAVACMD" "$@"
diff --git a/lesson_25/db/gradlew.bat b/lesson_25/db/gradlew.bat
new file mode 100644
index 000000000..9d21a2183
--- /dev/null
+++ b/lesson_25/db/gradlew.bat
@@ -0,0 +1,94 @@
+@rem
+@rem Copyright 2015 the original author or authors.
+@rem
+@rem Licensed under the Apache License, Version 2.0 (the "License");
+@rem you may not use this file except in compliance with the License.
+@rem You may obtain a copy of the License at
+@rem
+@rem      https://www.apache.org/licenses/LICENSE-2.0
+@rem
+@rem Unless required by applicable law or agreed to in writing, software
+@rem distributed under the License is distributed on an "AS IS" BASIS,
+@rem WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+@rem See the License for the specific language governing permissions and
+@rem limitations under the License.
+@rem
+@rem SPDX-License-Identifier: Apache-2.0
+@rem
+
+@if "%DEBUG%"=="" @echo off
+@rem ##########################################################################
+@rem
+@rem  Gradle startup script for Windows
+@rem
+@rem ##########################################################################
+
+@rem Set local scope for the variables with windows NT shell
+if "%OS%"=="Windows_NT" setlocal
+
+set DIRNAME=%~dp0
+if "%DIRNAME%"=="" set DIRNAME=.
+@rem This is normally unused
+set APP_BASE_NAME=%~n0
+set APP_HOME=%DIRNAME%
+
+@rem Resolve any "." and ".." in APP_HOME to make it shorter.
+for %%i in ("%APP_HOME%") do set APP_HOME=%%~fi
+
+@rem Add default JVM options here. You can also use JAVA_OPTS and GRADLE_OPTS to pass JVM options to this script.
+set DEFAULT_JVM_OPTS="-Xmx64m" "-Xms64m"
+
+@rem Find java.exe
+if defined JAVA_HOME goto findJavaFromJavaHome
+
+set JAVA_EXE=java.exe
+%JAVA_EXE% -version >NUL 2>&1
+if %ERRORLEVEL% equ 0 goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is not set and no 'java' command could be found in your PATH. 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:findJavaFromJavaHome
+set JAVA_HOME=%JAVA_HOME:"=%
+set JAVA_EXE=%JAVA_HOME%/bin/java.exe
+
+if exist "%JAVA_EXE%" goto execute
+
+echo. 1>&2
+echo ERROR: JAVA_HOME is set to an invalid directory: %JAVA_HOME% 1>&2
+echo. 1>&2
+echo Please set the JAVA_HOME variable in your environment to match the 1>&2
+echo location of your Java installation. 1>&2
+
+goto fail
+
+:execute
+@rem Setup the command line
+
+set CLASSPATH=%APP_HOME%\gradle\wrapper\gradle-wrapper.jar
+
+
+@rem Execute Gradle
+"%JAVA_EXE%" %DEFAULT_JVM_OPTS% %JAVA_OPTS% %GRADLE_OPTS% "-Dorg.gradle.appname=%APP_BASE_NAME%" -classpath "%CLASSPATH%" org.gradle.wrapper.GradleWrapperMain %*
+
+:end
+@rem End local scope for the variables with windows NT shell
+if %ERRORLEVEL% equ 0 goto mainEnd
+
+:fail
+rem Set variable GRADLE_EXIT_CONSOLE if you need the _script_ return code instead of
+rem the _cmd.exe /c_ return code!
+set EXIT_CODE=%ERRORLEVEL%
+if %EXIT_CODE% equ 0 set EXIT_CODE=1
+if not ""=="%GRADLE_EXIT_CONSOLE%" exit %EXIT_CODE%
+exit /b %EXIT_CODE%
+
+:mainEnd
+if "%OS%"=="Windows_NT" endlocal
+
+:omega
diff --git a/lesson_25/db/settings.gradle.kts b/lesson_25/db/settings.gradle.kts
new file mode 100644
index 000000000..68449d331
--- /dev/null
+++ b/lesson_25/db/settings.gradle.kts
@@ -0,0 +1,13 @@
+/*
+ * This file was generated by the Gradle 'init' task.
+ *
+ * The settings file is used to specify which projects to include in your build.
+ *
+ * Detailed information about configuring a multi-project build in Gradle can be found
+ * in the user manual at https://docs.gradle.org/8.0.2/userguide/multi_project_builds.html
+ */
+
+includeBuild("../../lib/java/codedifferently-instructional")
+
+rootProject.name = "lesson_25"
+include("db_app")