Feat: spring data jpa - InheritanceType.JOINED

spring-data-jpa/README.md

@@ -16,15 +16,46 @@
 - 사용되는 어노테이션
     - `@PrimaryKeyJoinColumn, @DiscriminatorColumn, @DiscriminatorValue`
 
+```java
+// Item.java
+@Entity
+@Inheritance(strategy = InheritanceType.JOINED)
+@DiscriminatorColumn(name = "DTYPE")
+public abstract class Item {
+
+  @Id @GeneratedValue
+  private long id;
+
+  private String name;
+  private int price;
+}
+
+// Album.java
+@Entity
+@DiscriminatorValue("A")
+public class Album extends Item {
+
+  private String artist;
+}
+
+// Book.java
+@Entity
+@DiscriminatorValue("B")
+public class Book extends Item {
+
+  private String author;
+}
+```
+
 ### 2. 단일테이블 전략 (`InheritanceType.SINGLE_TABLE`)
 - 이름 그래도 테이블을 하나만 사용하는 방식이다
 - 또한 `조인전략`과 마찬가지로 구분칼럼(`DTYPE`)을 이용해서 어떤 자식데이터가 저장되었는지 구분한다
 - 장점
-    - 조회할 때 조인을 사용하지 않으므로 일반적으로 가장 빠르다
+    - 조회할 때 조인을 사용하지 않으므로 가장 빠르다
     - 조회 쿼리가 단순하다
 - 단점
     - 자식 엔티티가 매핑한 컬럼은 모두 null 허용해야한다
-    - 한 테이블에 모두 저장하므로 테이블이 의도치않게 커질 수 있다. 즉 변경과 확장에 취약해지게 된다.
+    - 한 테이블에 모두 저장하므로 테이블이 의도치않게 커질 수 있다. 변경과 확장에 취약해지게 된다.
 
 ```java
 // Item.java

spring-data-jpa/src/main/java/com/example/demo/controller/CreateAlbumDto.java

@@ -1,5 +1,6 @@
 package com.example.demo.controller;
 
+import com.example.demo.domain.joined.JoinedAlbum;
 import com.example.demo.domain.singletable.SingleTableAlbum;
 import com.example.demo.domain.tableperclass.TablePerClassAlbum;
 import lombok.AllArgsConstructor;
@@ -22,4 +23,8 @@ public SingleTableAlbum toSingleTableEntity() {
     public TablePerClassAlbum toTablePerClassEntity() {
         return new TablePerClassAlbum(name, price, artist);
     }
+
+    public JoinedAlbum toJoinedEntity() {
+        return new JoinedAlbum(name, price, artist);
+    }
 }

spring-data-jpa/src/main/java/com/example/demo/controller/TestController.java

@@ -1,10 +1,13 @@
 package com.example.demo.controller;
 
+import com.example.demo.controller.dto.joined.GetJoinedAlbumDto;
 import com.example.demo.controller.dto.singletable.GetSingleTableAlbumDto;
 import com.example.demo.controller.dto.tableperclass.GetTablePerClassAlbumDto;
+import com.example.demo.domain.joined.JoinedAlbum;
 import com.example.demo.domain.singletable.SingleTableAlbum;
 import com.example.demo.domain.singletable.SingleTableItem;
 import com.example.demo.domain.tableperclass.TablePerClassAlbum;
+import com.example.demo.repository.joined.JoinedAlbumRepository;
 import com.example.demo.repository.singletable.SingleTableAlbumRepository;
 import com.example.demo.repository.tableperclass.TablePerClassAlbumRepository;
 import lombok.RequiredArgsConstructor;
@@ -16,6 +19,7 @@ public class TestController {
 
     private final SingleTableAlbumRepository singleTableAlbumRepository;
     private final TablePerClassAlbumRepository tablePerClassAlbumRepository;
+    private final JoinedAlbumRepository joinedAlbumRepository;
 
     @PostMapping("/single/album")
     public long createSingleTableAlbum(@RequestBody CreateAlbumDto body) {
@@ -29,6 +33,12 @@ public long createTablePerClassAlbum(@RequestBody CreateAlbumDto body) {
         return entity.getId();
     }
 
+    @PostMapping("/joined/album")
+    public long createJoinedAlbum(@RequestBody CreateAlbumDto body) {
+        JoinedAlbum entity = joinedAlbumRepository.save(body.toJoinedEntity());
+        return entity.getId();
+    }
+
     @GetMapping("/single/album")
     public GetSingleTableAlbumDto getSingleTableAlbum(@RequestParam long id) {
         return new GetSingleTableAlbumDto(singleTableAlbumRepository.findById(id).orElseThrow());
@@ -38,4 +48,9 @@ public GetSingleTableAlbumDto getSingleTableAlbum(@RequestParam long id) {
     public GetTablePerClassAlbumDto getTablePerClassAlbum(@RequestParam long id) {
         return new GetTablePerClassAlbumDto(tablePerClassAlbumRepository.findById(id).orElseThrow());
     }
+
+    @GetMapping("/joined/album")
+    public GetJoinedAlbumDto getJoinedAlbum(@RequestParam long id) {
+        return new GetJoinedAlbumDto(joinedAlbumRepository.findById(id).orElseThrow());
+    }
 }

spring-data-jpa/src/main/java/com/example/demo/controller/dto/joined/GetJoinedAlbumDto.java

@@ -0,0 +1,21 @@
+package com.example.demo.controller.dto.joined;
+
+import com.example.demo.domain.joined.JoinedAlbum;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+
+@Getter
+@NoArgsConstructor
+public class GetJoinedAlbumDto {
+    private long id;
+    private String name;
+    private int price;
+    private String artist;
+
+    public GetJoinedAlbumDto(JoinedAlbum entity) {
+        this.id = entity.getId();
+        this.name = entity.getName();
+        this.price = entity.getPrice();
+        this.artist = entity.getArtist();
+    }
+}

spring-data-jpa/src/main/java/com/example/demo/domain/joined/JoinedAlbum.java

@@ -0,0 +1,22 @@
+package com.example.demo.domain.joined;
+
+import jakarta.persistence.DiscriminatorValue;
+import jakarta.persistence.Entity;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.ToString;
+
+@Entity
+@Getter
+@ToString
+@NoArgsConstructor
+@DiscriminatorValue("A")
+public class JoinedAlbum extends JoinedItem {
+
+    private String artist;
+
+    public JoinedAlbum(String name, int price, String artist) {
+        super(name, price);
+        this.artist = artist;
+    }
+}

spring-data-jpa/src/main/java/com/example/demo/domain/joined/JoinedBook.java

@@ -0,0 +1,11 @@
+package com.example.demo.domain.joined;
+
+import jakarta.persistence.DiscriminatorValue;
+import jakarta.persistence.Entity;
+
+@Entity
+@DiscriminatorValue("B")
+public class JoinedBook extends JoinedItem {
+
+    private String author;
+}

spring-data-jpa/src/main/java/com/example/demo/domain/joined/JoinedItem.java

@@ -0,0 +1,26 @@
+package com.example.demo.domain.joined;
+
+import jakarta.persistence.*;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.ToString;
+
+@Entity
+@Getter
+@ToString
+@NoArgsConstructor
+@Inheritance(strategy = InheritanceType.JOINED)
+@DiscriminatorColumn(name = "DTYPE")
+public abstract class JoinedItem {
+
+    @Id @GeneratedValue
+    private long id;
+
+    private String name;
+    private int price;
+
+    public JoinedItem(String name, int price) {
+        this.name = name;
+        this.price = price;
+    }
+}

spring-data-jpa/src/main/java/com/example/demo/domain/joined/JoinedMovie.java

@@ -0,0 +1,10 @@
+package com.example.demo.domain.joined;
+
+import jakarta.persistence.DiscriminatorValue;
+import jakarta.persistence.Entity;
+
+@Entity
+@DiscriminatorValue("M")
+public class JoinedMovie extends JoinedItem {
+    private String director;
+}

spring-data-jpa/src/main/java/com/example/demo/repository/joined/JoinedAlbumRepository.java

@@ -0,0 +1,7 @@
+package com.example.demo.repository.joined;
+
+import com.example.demo.domain.joined.JoinedAlbum;
+import org.springframework.data.jpa.repository.JpaRepository;
+
+public interface JoinedAlbumRepository extends JpaRepository<JoinedAlbum, Long> {
+}