JPA Persist parent and child with one to many relationship

Question

I want to persist parent entity with 20 child entities, my code is below

Parent Class

@OneToMany(mappedBy = \"parentId\")
private Collection

        

Answer 1

Fix your Parent class:

@OneToMany(mappedBy = "parent")

mappedBy property should point to field on other side of relationship. As JavaDoc says:

The field that owns the relationship. Required unless the relationship is unidirectional.

Also you should explicitely persist Child entity in cycle:

for(Child tha : parent.getChildCollection()) { 
    ...
    getEntityManager().persist(tha);
    ...
}

As Alan Hay noticed in comment, you can use cascade facilities and let EntityManager automatically persist all your Child entities:

@OneToMany(mappedBy = "parent", cascade = CascadeType.PERSIST)

More details about cascades (and JPA itself) you can find in Vlad Mihalcea's blog.