All-

I have this recent problem that I cannot seem to wrap my head around and - in six years of using hibernate haven't ever run into...

I have a bi-directional relationship between Union 1--∞ Chapter. When I create a Union object, instantiate the set (or list, even), create a new chapter and set that chapter on the set -- I get an exception where the UNION_ID on the Chapter object is null. I've been spinning my wheels for hours trying to determine what's going on. The relevant portion of the mapping is below...

... Union {
@OneToMany(mappedBy = "union", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
private Set<Chapter> chapters;
}

... Chapter {
@ManyToOne
@JoinColumn(name = "UNION_ID", nullable = false)
private Union union;
}

... and, of course, the relevant, public getters and setters

... execution code looks more or less like...

Union myUnion = new Union();
Chapter myChapter = new Chapter();
Set<Chapter> chapters = new HashSet<Chapter>();
chapters.add(myChapter);

unionService.persist(myUnion);

...

At this point, the transaction fails because "UNION_ID" is NULL for the chapter insert, violating the schema.

Any thoughts???

You are missing at least two lines of code:

Ack. Yeah, I forgot to add that line to the post. So I am setting the chapters on the Union object.

I've _never_ had to manually set the parent on the child. Simply adding the child to a parent's List or Set member annotated as a @OneToMany did the trick.

Union myUnion = new Union();

Set<Chapter> chapters = new HashSet<Chapter>();
Chapter myChapter = new Chapter();
chapters.add(myChapter);

---> FORGOT LINE ---> myUnion.setChapters(chapters);

unionService.persist(myUnion);

---

So when did it become a requirement that you have to manage both sides of the relationship?

As far as I know it has always been required that the owning side of the association is properly set. In this case it is the Chapter that owns the link, so myChapter.setUnion() must be called.

So... There are two things that are different about this project; (a) I'm using spring mvc 3.0 instead of struts 2.1.x and (b) I'm using JPA 2 instead of pure hibernate (I think the last project was 3.3). I'm starting to get the feeling that maybe Struts was setting the relationship for me? -- especially when the type is a list. In my form I'd have something like...



... which would automagically instantiate the concrete list on the Union, create ONE chapter object ... and set the union on the chapter? Then in the struts action you have a getter for "union", type Union, which would be the object all rolled up.