[jboss-user] [EJB 3.0] - EJB 3.0 Persistence with Parent/Child and composite keys

I have a fairly common scenario which I am having trouble getting to work as I expect. I have searched through the documentation and forums, but have not yet found any information which helped be with my issue. I have two tables, lets call them PARENT and CHILD in a MySQL database. | ------------------ | | PARENT | | ------------------ | | PARENT_ID (PK) | | | <attributes> | | ------------------ | | ------------------ | | CHILD | | ------------------ | | PARENT_ID (PK) | | | CHILD_ID (PK) | | | <attributes> | | ------------------ | I also have entity classes for these two tables - | @Entity | @Table(name="parent") | public class Parent implements Serializable { | @Id | @GeneratedValue | @Column(name="parent_id") | private int parentId; | | @OneToMany(cascade={CascadeType.ALL}) | @JoinColumn(name="parent_id") | private List<Child> children; | | //getters,setters,etc. | } | | @Entity | @Table(name="child") | public class Child implements Serializable { | @EmbeddedId | private ChildId childId; | | //getters, setters, hashCode, equals, etc | } | | @Embeddable | public class ChildId implements Serializable { | @Column(name="parent_id") | private int parentId; | | @Column(name="child_id") | private int childId; | | //getters, setters, hashCode, equals, etc. | } | So far, this seems pretty straight forward, and I believe gives me what I want. If I create a new Parent object, add child objects and merge, it appears to save, although in a strange fashion. (Note: I am using merge, as in the general case, these may or may not be new objects). The (paraphrased) SQL which is generated using hibernate is - | insert on PARENT. | insert on CHILD set PARENT_ID = 0 and CHILD_ID = <correct child_id>. | update on CHILD set PARENT_ID = <correct parent_id> and CHILD_ID = <correct child_id> where PARENT_ID = 0 and CHILD_ID = <correct child_id> | This does appear to get the job done, but I run into a major problem when I try to insert two parent_ids where child_id has the same value. For example, if I have a Parent1 with a Child1 and a Child2 and a Parent2 with a Child2 (different object, same CHILD_ID) and a Child3 I get the following statements (paraphrased)- | insert on PARENT. | insert on PARENT. | insert on CHILD set PARENT_ID = 0 and CHILD_ID = 1 | insert on CHILD set PARENT_ID = 0 and CHILD_ID = 2 | insert on CHILD set PARENT_ID = 0 and CHILD_ID = 2 (not sure why this doesn't fail... i believe its done via a batch insert?) | insert on CHILD set PARENT_ID = 0 and CHILD_ID = 3 | update on CHILD set PARENT_ID = 1 where PARENT_ID = 0 and CHILD_ID = 1 | update on CHILD set PARENT_ID = 1 where PARENT_ID = 0 and CHILD_ID = 2 | update on CHILD set PARENT_ID = 2 where PARENT_ID = 0 and CHILD_ID = 2 | update on CHILD set PARENT_ID = 2 where PARENT_ID = 0 and CHILD_ID = 3 | It then throws an exception because the update expected to change one row, and it changed none (the third update statement has no effect). I am using JBoss 4.2 and SEAM 2.0 out of the box. I am not clear what I am doing wrong. I assume that the insert with parent_id is 0 is because there is no parent_id set on the child object. I would also assume that the persistence manager would be responsible for setting this after the parent objects are inserted. I would prefer not to have a backwards reference from the child object back to the parent object, as this seems redundant, and will never be used in this context. Am I missing an annotation, or annotation parameter somewhere which will get me the expected behavior? (I would expect to see only 2 parent and 4 child inserts, with no updates at all). Am I forced to flush the persistence manager between each merge(parent) call? Thanks for your help, Jason View the original post : http://www.jboss.com/index.html?module=bb&op=viewtopic&p=4116880#... Reply to the post : http://www.jboss.com/index.html?module=bb&op=posting&mode=reply&a...