I am trying to create a simple CRUD application using Spring Boot with User, UserEntity, Post, Comment entities.
-> UserEntity is super class of Comment and Post.
-> Each comment has a ManyToOne relationship to a UserEntity (which can be a Post or another Comment)
UserEntity
???|
???@ManyToOne
???createdBy - refers to user table (id)
???|
--------------------
| ? ?????|
| ?????? |
Post ?? Comment
????????|
????????@ManytoOne
??????????UserEntity - refers to PK(entity_id) of user_entity table as comment can be on post or reply to another comment
On trying to save a comment on post from the CommentService class,
//Controller
@PostMapping(path = "api/v1/addComment")
public void addComment(@RequestBody Comment comment){ commentService.addCommentOnPost(comment); }
//Service
public void addCommentOnEntity(Comment comment){ commentRepos.save(comment); }
the foreign key in comment table (parent_entity_id) referring to entity_id in user_entity table is not getting updated. The value is blank.
On the other hand UserEntity has a manytoone relationship with User -- createdBy -- which is updating foriegn key user_id in user_entity table properly
Can someone guide me what could be wrong, I have been trying since yesterday night but no luck. Have checked some other answers but could not get an answer for this case.
User.java
@Entity
@Table(name="[user]")
public class User {
@Id
@SequenceGenerator(name="student_sequence",
sequenceName = "student_sequence",
allocationSize = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE,
generator = "student_sequence")
private long id;
private String name;
private String email;
private int age;
private LocalDate DOB;
//Setters and Getters and default constructor
}
UserEntity.java
@Entity
@Inheritance(strategy = InheritanceType.JOINED)
public abstract class UserEntity {
@Id
@SequenceGenerator(sequenceName = "entity_sequence", name="entity_sequence", allocationSize = 1)
@GeneratedValue(strategy = GenerationType.SEQUENCE, generator = "post_sequence")
private long entityId;
private char entityType;
private LocalDate createdOn;
private LocalDate modifiedOn;
@ManyToOne
@JoinColumn(name = "user_id", referencedColumnName = "id")
private User createdBy;
//Setters and Getters and default constructor
}
Post.java
@Entity
public class Post extends UserEntity{
private String postHeading;
private String postBody;
//Setters and Getters and default constructor
}
Comment.java
@Entity
public class Comment extends UserEntity{
private String comment;
@ManyToOne
@JoinColumn(name="parent_entity_id", referencedColumnName = "entityId")
private UserEntity parentEntity;
//Setters and Getters and default constructor
}
and their repositories
@NoRepositoryBean
public interface UserEntityBaseRepos<T extends UserEntity> extends JpaRepository<T, Long>{
Optional<List<T>> findByCreatedBy_Id(Long user_id);
Optional<List<T>> findByEntityId(Long entity_id);
}
@Repository
public interface UserRespository extends JpaRepository<User, Long> {
Optional<User> findUserByEmail(String email);
Optional<User> findUserByName(String name);
}
@Repository
public interface PostRepos extends UserEntityBaseRepos<Post>, JpaRepository<Post, Long> {
}
@Repository
public interface CommentRepos extends UserEntityBaseRepos<Comment>, JpaRepository<Comment, Long> {
}
Json for postComment service
{
"entityType" : "C",
"createdOn" : "2020-02-05",
"createdBy" : {
"id" : 1
},
"comment": "I am the comment",
"parentEntity" : {
"entityId" : 1
}
}
//User with id = 1 and UserEntity(Post) with entityId = 1 available in database.
Here createdBy.id (user id) is getting updated in the user_entity table, but userEntity.entityId is not getting updated in the comment table
question from:
https://stackoverflow.com/questions/66060767/issue-in-persisting-nested-comments-using-spring-hibernate 
