JPA OneToMany and ManyToOne throw Repeated column in mapping for entity column should be mapped with insert false update false

Question

I have three classes one of the names is User and this user has other classes instances  Like this  public class User       OneToMany fetch FetchType LAZY  cascade   CascadeType ALL      public List lt APost gt  aPosts        OneToMany fetch FetchType LAZY  cascade   CascadeType ALL      public List lt BPost gt  bPosts           public class BPost extends Post             ManyToOne fetch FetchType LAZY          public User user              public class APost extends Post              ManyToOne fetch FetchType LAZY        public User user      it s working like this but generates empty tables in DB  Which have to contain foreign keys  When I tried to use mappedBy and JoinColumn annotations I got failed  How can I resolve this  Extra information  When I changed with    ManyToOne fetch FetchType LAZY    JoinColumn name  quot id quot    public User user   and   OneToMany fetch FetchType LAZY  cascade   CascadeType ALL  mappedBy  quot id quot    public List lt APost gt  aPosts   I m getting A JPA error occurred  Unable to build EntityManagerFactory   Repeated column in mapping for entity  models post APost column  id  should be mapped with insert  quot false quot  update  quot false quot   Final Edit  Finally  I was totally wrong about JPA annotations     When I change  OneToMany fetch FetchType LAZY  cascade   CascadeType ALL  mappedBy  quot id quot    to  OneToMany fetch FetchType LAZY  cascade   CascadeType ALL  mappedBy  quot user quot    and  ManyToOne fetch FetchType LAZY   JoinColumn name  quot user id quot    everything works ok

User · Answer

I am not really sure about your question (the meaning of "empty table" etc, or how mappedBy and JoinColumn were not working).

I think you were trying to do a bi-directional relationships.

First, you need to decide which side "owns" the relationship. Hibernate is going to setup the relationship base on that side. For example, assume I make the Post side own the relationship (I am simplifying your example, just to keep things in point), the mapping will look like:

(Wish the syntax is correct. I am writing them just by memory. However the idea should be fine)

public class User{
    @OneToMany(fetch=FetchType.LAZY, cascade = CascadeType.ALL, mappedBy="user")
    private List<Post> posts;
}


public class Post {
    @ManyToOne(fetch=FetchType.LAZY)
    @JoinColumn(name="user_id")
    private User user;
}

By doing so, the table for Post will have a column user_id which store the relationship. Hibernate is getting the relationship by the user in Post (Instead of posts in User. You will notice the difference if you have Post's user but missing User's posts).

You have mentioned mappedBy and JoinColumn is not working. However, I believe this is in fact the correct way. Please tell if this approach is not working for you, and give us a bit more info on the problem. I believe the problem is due to something else.

Edit:

Just a bit extra information on the use of mappedBy as it is usually confusing at first. In mappedBy, we put the "property name" in the opposite side of the bidirectional relationship, not table column name.

User · Answer

You should never use the unidirectional  OneToMany annotation because   It generates inefficient SQL statements It creates an extra table which increases the memory footprint of your DB indexes  Now  in your first example  both sides are owning the association  and this is bad  While the  JoinColumn would let the  OneToMany side in charge of the association  it s definitely not the best choice  Therefore  always use the mappedBy attribute on the  OneToMany side  public class User       OneToMany fetch FetchType LAZY  cascade   CascadeType ALL  mappedBy  quot user quot       public List lt APost gt  aPosts        OneToMany fetch FetchType LAZY  cascade   CascadeType ALL  mappedBy  quot user quot       public List lt BPost gt  bPosts     public class BPost extends Post         ManyToOne fetch FetchType LAZY          public User user     public class APost extends Post          ManyToOne fetch FetchType LAZY        public User user

[java] JPA OneToMany and ManyToOne throw: Repeated column in mapping for entity column (should be mapped with insert="false" update="false")

Examples related to java

Examples related to hibernate

Examples related to jpa

Examples related to one-to-many

Examples related to many-to-one