如何在Hibernate中级联删除集合？

Question

Let's say I have two entities, a Post and a Comment (in ColdFusion):

component persistent="true" table="post"
{
    property name="Id" fieldtype="id";
    property name="Comments" fieldtype="one-to-many" cfc="Comment" fkcolumn="post_id" cascade="all";
}

component persistent="true" table="comment"
{
    property name="Id" fieldtype="id";
    property name="Post" fieldtype="many-to-one" cfc="Post" column="post_id";
}

Post has a collection of Comments . Now I'd like to delete a Post , and have the Comments automatically deleted as well. I've tried the straightforward method:

var post = EntityLoadByPK("Post", 13);
EntityDelete(post);

But I'm getting a Hibernate error that says that post_id cannot be set to null. What am I doing wrong, and how can I fix this issue?

Answer 1

You need to adjust your mappings. Try making the Post property of comment not null and marking the Comments property of post as inverse.

component persistent="true" table="post"
{
  property name="Id" fieldtype="id";
  property name="Comments" fieldtype="one-to-many" cfc="Comment" fkcolumn="post_id" cascade="all" inverse="true";
}

component persistent="true" table="comment"
{
  property name="Id" fieldtype="id";
  property name="Post" fieldtype="many-to-one" cfc="Post" column="post_id" notnull="true";
}

Answer 2

You'll have to make post_id in Comment table nullable in your DB. That's how hibernate does cascade delete. It'll set all Comments with post_id = 13 as null, then delete all comments where post_id IS NULL