From 9a67a37647806eef1fc92f50d929e0f12bbc7b94 Mon Sep 17 00:00:00 2001
From: yueunfive <122276414+yueunfive@users.noreply.github.com>
Date: Thu, 27 Nov 2025 21:18:58 +0900
Subject: [PATCH 1/2] piki-logan

---
 .idea/gradle.xml                              |  2 +-
 .idea/misc.xml                                |  2 +-
 .../yourssu/entitymanager/EntityManager.java  |  6 ++
 .../entitymanager/EntityManagerImpl.java      | 65 +++++++++++++++++++
 .../java/com/yourssu/entitymanager/Main.java  | 34 ++++++++++
 .../java/com/yourssu/entitymanager/User.java  | 19 ++++++
 .../entitymanager/UserRespository.java        | 19 ++++++
 .../entitymanager/UserRespositoryTest.java    |  8 +++
 8 files changed, 153 insertions(+), 2 deletions(-)
 create mode 100644 src/main/java/com/yourssu/entitymanager/EntityManager.java
 create mode 100644 src/main/java/com/yourssu/entitymanager/EntityManagerImpl.java
 create mode 100644 src/main/java/com/yourssu/entitymanager/Main.java
 create mode 100644 src/main/java/com/yourssu/entitymanager/User.java
 create mode 100644 src/main/java/com/yourssu/entitymanager/UserRespository.java
 create mode 100644 src/test/java/com/yourssu/entitymanager/UserRespositoryTest.java

diff --git a/.idea/gradle.xml b/.idea/gradle.xml
index 2a65317..f722030 100644
--- a/.idea/gradle.xml
+++ b/.idea/gradle.xml
@@ -5,7 +5,7 @@
     <option name="linkedExternalProjectsSettings">
       <GradleProjectSettings>
         <option name="externalProjectPath" value="$PROJECT_DIR$" />
-        <option name="gradleHome" value="" />
+        <option name="gradleJvm" value="openjdk-20" />
         <option name="modules">
           <set>
             <option value="$PROJECT_DIR$" />
diff --git a/.idea/misc.xml b/.idea/misc.xml
index 32cf4db..4397734 100644
--- a/.idea/misc.xml
+++ b/.idea/misc.xml
@@ -4,7 +4,7 @@
   <component name="FrameworkDetectionExcludesConfiguration">
     <file type="web" url="file://$PROJECT_DIR$" />
   </component>
-  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" default="true" project-jdk-name="corretto-21" project-jdk-type="JavaSDK">
+  <component name="ProjectRootManager" version="2" languageLevel="JDK_21" project-jdk-name="openjdk-20" project-jdk-type="JavaSDK">
     <output url="file://$PROJECT_DIR$/out" />
   </component>
 </project>
\ No newline at end of file
diff --git a/src/main/java/com/yourssu/entitymanager/EntityManager.java b/src/main/java/com/yourssu/entitymanager/EntityManager.java
new file mode 100644
index 0000000..f785697
--- /dev/null
+++ b/src/main/java/com/yourssu/entitymanager/EntityManager.java
@@ -0,0 +1,6 @@
+package com.yourssu.entitymanager;
+
+public interface EntityManager {
+    public void persist(Object entity);
+    public <T> T merge(T entity);
+}
diff --git a/src/main/java/com/yourssu/entitymanager/EntityManagerImpl.java b/src/main/java/com/yourssu/entitymanager/EntityManagerImpl.java
new file mode 100644
index 0000000..2d93b64
--- /dev/null
+++ b/src/main/java/com/yourssu/entitymanager/EntityManagerImpl.java
@@ -0,0 +1,65 @@
+package com.yourssu.entitymanager;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class EntityManagerImpl implements EntityManager {
+
+    private final Map<Long, User> persistenceContext = new HashMap<>();
+    private long sequence = 1L;
+
+    // id가 null일 때 호출 (비영속 → 영속)
+    @Override
+    public void persist(Object entity) {
+        if (!(entity instanceof User)) {
+            throw new IllegalArgumentException("일단은 User 엔티티만 지원합니다.");
+        }
+
+        User user = (User) entity;
+
+        if (user.getId() != null) {
+            throw new IllegalStateException("이미 ID가 존재하는 엔티티입니다. persist 불가.");
+        }
+
+        user.setId(sequence++);
+
+        persistenceContext.put(user.getId(), user);
+
+        System.out.println("[persist] 저장됨: " + user.getId() + ", " + user.getName());
+    }
+
+    // 이미 ID가 있는 객체일 때 (준영속 → 영속)
+    @Override
+    public <T> T merge(T entity) {
+        if (!(entity instanceof User)) {
+            throw new IllegalArgumentException("일단은 User 엔티티만 지원합니다.");
+        }
+
+        User detached = (User) entity;
+
+        if (detached.getId() == null) {
+            throw new IllegalStateException("ID가 없는 엔티티는 merge할 수 없습니다.");
+        }
+
+        User managed = persistenceContext.get(detached.getId());
+
+        if (managed == null) {
+            managed = new User();
+            managed.setId(detached.getId());
+            persistenceContext.put(managed.getId(), managed);
+        }
+        managed.setName(detached.getName());
+
+        System.out.println("[merge] 병합됨: " + managed.getId() + ", " + managed.getName());
+
+        return (T) managed;
+    }
+
+    public void printStore() {
+        System.out.println("== 현재 영속성 컨텍스트 상태 ==");
+        for (Map.Entry<Long, User> entry : persistenceContext.entrySet()) {
+            User u = entry.getValue();
+            System.out.println("id=" + u.getId() + ", name=" + u.getName());
+        }
+    }
+}
diff --git a/src/main/java/com/yourssu/entitymanager/Main.java b/src/main/java/com/yourssu/entitymanager/Main.java
new file mode 100644
index 0000000..1f42249
--- /dev/null
+++ b/src/main/java/com/yourssu/entitymanager/Main.java
@@ -0,0 +1,34 @@
+package com.yourssu.entitymanager;
+
+public class Main {
+    public static void main(String[] args) {
+
+        // EntityManager 구현체 생성
+        EntityManager em = new EntityManagerImpl();
+
+        // Repository 생성
+        UserRespository userRepository = new UserRespository(em);
+
+        // 1. 새로운 유저 (비영속 상태)
+        User user1 = new User();
+        user1.setName("김민수");
+
+        System.out.println("\n=== 1. persist 테스트 (신규 저장) ===");
+        userRepository.save(user1);  // persist 호출
+
+        // 2. 준영속 객체 시뮬레이션 (새 객체이지만 ID는 있음)
+        System.out.println("\n=== 2. merge 테스트 (준영속 -> 영속) ===");
+        User detachedUser = new User(user1.getId(), "이름 수정됨");
+        userRepository.save(detachedUser);  // merge 호출
+
+        // 3. 새로운 유저 추가
+        System.out.println("\n=== 3. 또 다른 유저 persist ===");
+        User user2 = new User();
+        user2.setName("박지성");
+        userRepository.save(user2);
+
+        // 4. 영속성 컨텍스트 내용 출력
+        System.out.println("\n=== 4. 영속성 컨텍스트 전체 출력 ===");
+        ((EntityManagerImpl) em).printStore();
+    }
+}
diff --git a/src/main/java/com/yourssu/entitymanager/User.java b/src/main/java/com/yourssu/entitymanager/User.java
new file mode 100644
index 0000000..649f7be
--- /dev/null
+++ b/src/main/java/com/yourssu/entitymanager/User.java
@@ -0,0 +1,19 @@
+package com.yourssu.entitymanager;
+
+public class User {
+    private Long id;
+    private String name;
+
+    public User() {}
+
+    public User(Long id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public Long getId() { return id; }
+    public void setId(Long id) { this.id = id; }
+
+    public String getName() { return name; }
+    public void setName(String name) { this.name = name; }
+}
diff --git a/src/main/java/com/yourssu/entitymanager/UserRespository.java b/src/main/java/com/yourssu/entitymanager/UserRespository.java
new file mode 100644
index 0000000..a89e1dc
--- /dev/null
+++ b/src/main/java/com/yourssu/entitymanager/UserRespository.java
@@ -0,0 +1,19 @@
+package com.yourssu.entitymanager;
+
+public class UserRespository {
+
+    private final EntityManager entityManager;
+
+    public UserRespository(EntityManager entityManager) {
+        this.entityManager = entityManager;
+    }
+
+    public void save(User user) {
+        if (user.getId() == null) {
+            entityManager.persist(user);
+        } else {
+            entityManager.merge(user);
+        }
+    }
+
+}
diff --git a/src/test/java/com/yourssu/entitymanager/UserRespositoryTest.java b/src/test/java/com/yourssu/entitymanager/UserRespositoryTest.java
new file mode 100644
index 0000000..78aed17
--- /dev/null
+++ b/src/test/java/com/yourssu/entitymanager/UserRespositoryTest.java
@@ -0,0 +1,8 @@
+package com.yourssu.entitymanager;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class UserRespositoryTest {
+
+
+}

From ea04544c9edf4fd4f741b5d7fc167c9869204e49 Mon Sep 17 00:00:00 2001
From: yueunfive <122276414+yueunfive@users.noreply.github.com>
Date: Thu, 27 Nov 2025 21:28:07 +0900
Subject: [PATCH 2/2] =?UTF-8?q?main=20=EC=A0=95=EB=A6=AC?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 .../java/com/yourssu/entitymanager/Main.java  | 25 +++++++------------
 1 file changed, 9 insertions(+), 16 deletions(-)

diff --git a/src/main/java/com/yourssu/entitymanager/Main.java b/src/main/java/com/yourssu/entitymanager/Main.java
index 1f42249..2ad0bb1 100644
--- a/src/main/java/com/yourssu/entitymanager/Main.java
+++ b/src/main/java/com/yourssu/entitymanager/Main.java
@@ -3,32 +3,25 @@
 public class Main {
     public static void main(String[] args) {
 
-        // EntityManager 구현체 생성
         EntityManager em = new EntityManagerImpl();
-
-        // Repository 생성
         UserRespository userRepository = new UserRespository(em);
 
-        // 1. 새로운 유저 (비영속 상태)
         User user1 = new User();
-        user1.setName("김민수");
+        user1.setName("피키");
 
-        System.out.println("\n=== 1. persist 테스트 (신규 저장) ===");
-        userRepository.save(user1);  // persist 호출
+        System.out.println("persist test");
+        userRepository.save(user1);
 
-        // 2. 준영속 객체 시뮬레이션 (새 객체이지만 ID는 있음)
-        System.out.println("\n=== 2. merge 테스트 (준영속 -> 영속) ===");
-        User detachedUser = new User(user1.getId(), "이름 수정됨");
-        userRepository.save(detachedUser);  // merge 호출
+        System.out.println("merge test");
+        User detachedUser = new User(user1.getId(), "이름 수정");
+        userRepository.save(detachedUser);
 
-        // 3. 새로운 유저 추가
-        System.out.println("\n=== 3. 또 다른 유저 persist ===");
+        System.out.println("또 다른 유저 persist");
         User user2 = new User();
-        user2.setName("박지성");
+        user2.setName("로건");
         userRepository.save(user2);
 
-        // 4. 영속성 컨텍스트 내용 출력
-        System.out.println("\n=== 4. 영속성 컨텍스트 전체 출력 ===");
+        System.out.println("영속성 컨텍스트 전체 출력");
         ((EntityManagerImpl) em).printStore();
     }
 }