adds jedis docs

Author: nimonian

src/javalin/redis.md

@@ -0,0 +1,151 @@
+# Redis
+
+## Install Redis
+
+There are a few ways of
+[installing Redis itself](https://redis.io/docs/latest/operate/oss_and_stack/install/).
+
+::: tip
+
+Note that Redis is a lightweight version, whereas Redis Stack contains more
+features.
+
+:::
+
+If you are using Docker, you should be able to access Redis without explicitly
+running it. If you have installed natively, you may need to run it:
+
+::: code-group
+
+```bash
+redis-server
+```
+
+```bash
+# if using redis stack
+redis-stack-server
+```
+
+:::
+
+## Install Redis Client
+
+There is a client library for Java called Jedis which makes developing against a
+Redis database much easier.
+
+To install it, add the following dependency to your `pom.xml`:
+
+```xml
+<dependency>
+    <groupId>redis.clients</groupId>
+    <artifactId>jedis</artifactId>
+    <version>5.2.0</version>
+</dependency>
+```
+
+## Basic operations
+
+```java
+package org.example;
+import redis.clients.jedis.UnifiedJedis;
+
+public class Main {
+    public static void main(String[] args) {
+        // Connect to Redis
+        UnifiedJedis jedis = new UnifiedJedis("redis://localhost:6379");
+
+        // Set a key/value pair
+        String res1 = jedis.set("bike:1", "Deimos");
+        System.out.println(res1); // OK
+
+        // Get a value for a specific key
+        String res2 = jedis.get("bike:1");
+        System.out.println(res2); // Deimos
+
+        // Close the connection
+        jedis.close();
+    }
+}
+```
+
+## Working with JSON
+
+Redis can store JSON data without stringifying it. Effectively, this makes Redis
+a document store.
+
+First, we create a JSON `object`:
+
+```java
+import org.json.JSONObject;
+
+JSONObject userJSON = new JSONObject()
+  .put("name", "Jane Doe")
+  .put("email", "[email protected]")
+  .put("age", 25)
+```
+
+Then, we add the user's json to the database:
+
+```java
+import redis.clients.jedis.json.Path2;
+
+String res1 = jedis.jsonSet("user:1", new Path2("$"), userJSON); // OK
+
+String res2 = jedis.jsonGet("user:1")
+// {"name": "Jane Doe", "email": "[email protected]", "age": 25}
+```
+
+Note that using `$` as the path means that this JSON is set at the root of the
+key `user:1`. However, the keys can be manipulated individually.
+
+```java
+String res1 = jedis.jsonSet("user:1", new Path2("$.age"), 26); // OK
+
+String res2 = jedis.jsonGet("user:1")
+// {"name": "Jane Doe", "email": "[email protected]", "age": 26}
+```
+
+## Search index
+
+We can create a search index which allows us to implement full-text search:
+
+```java
+import redis.clients.jedis.search.*;
+import redis.clients.jedis.search.aggr.*;
+import redis.clients.jedis.search.schemafields.*;
+
+SchemaField[] schema = {
+  TextField.of("$.name").as("name"),
+  NumericField.of("$.age").as("age")
+};
+
+String createResult = jedis.ftCreate("idx:users",
+  FTCreateParams.createParams()
+    .on(IndexDataType.JSON)
+    .addPrefix("user:"),
+    schema
+);
+
+System.out.println(createResult); // >>> OK
+```
+
+Note that `addPrefix("user:")` restricts the index to include only documents
+whose key begins with `user:`, which makes it more efficient.
+
+Now, we can use the search index. For example, here is how to get all users aged
+from 20 to 30:
+
+```java
+import java.util.List;
+
+SearchResult searchResult = jedis.ftSearch("idx:users", "@age:[20 30]");
+
+for (Document doc: searchResult.getdocuments()) {
+    System.out.println(doc.getId());
+}
+
+// users:1
+```
+
+To construct more complex queries, check out the
+[redis query engine](https://redis.io/docs/latest/develop/interact/search-and-query/).