JPA Exception saving parent/children

Question

I am using JPA and have the following:

ProductEntity 

@Basic
@Column(name = "PRODUCT_ID", nullable = false, length = 128)
private String productId;

@ManyToOne
@JoinColumn(name = "PARENT_ID")
private ProductEntity parent;

As you can see the product table can have a parent. Effectively a parent child relationship.

I have a product saved in the database, then I add some child products, each having the same parent.

• The parent Product has ProductEntity parent = null;

• The child Products have ProductEntity parent = the parent Product;

  ProductEntity parentProductEntity = ...
  ProductEntity childProductEntity1 = ...
  ProductEntity childProductEntity2 = ...
  
  em.persist(parentProductEntity);
  childProductEntity1.setParent(parentProductEntity);
  childProductEntity2.setParent(parentProductEntity);
  em.merge(childProductEntity1);
  

Data (it never inserts the last two child rows)

    ID        PRODUCT_ID     PARENT_ID
     1           1              null
     2           2                1
     3           3                1

Problem

I then try save each child Product. But I get an error indicating that there is a duplicate key (productId). When saving the child, it is trying to save a duplicate entry of the parent too.

Caused by: org.postgresql.util.PSQLException: ERROR: duplicate key value violates unique constraint "t_osm_product_product_id_uindex"

Question

How must I change what I am doing to successfully save each child Product?

Thanks

Answer 1

your entity should look like this

@Id
Long ID;

@Column(name = "PRODUCT_ID", nullable = false, length = 128)
private String productId;

@ManyToOne
@JoinColumn(name = "PARENT_ID")
private ProductEntity parent;

everything else seems fine in your code.

Data will look like this in the database

 ID        PRODUCT_ID     PARENT_ID
 1           abc              null
 2           def                1
 3           xyz                1