I have an entity class Foo foo that contains Collection<Bar> bars. I've tried a variety of ways, but I'm unable to successfully update my collection.

One attempt:

foo = em.find(key);
foo.getBars().clear();
foo.setBars(bars);
em.flush;  \\ commit, etc.

This appends the new collection to the old one.

Another attempt:

foo = em.find(key);
bars = foo.getBars();
for (Bar bar : bars) {
    em.remove(bar);
}
em.flush;  

At this point, I thought I could add the new collection, but I find that the entity foo has been wiped out.

Here are some annotations. In Foo:

@OneToMany(cascade = { CascadeType.ALL }, mappedBy = "foo")
private List<Bar> bars;

In Bar:

@ManyToOne(optional = false, cascade = { CascadeType.ALL })
@JoinColumn(name = "FOO_ID")
private Foo foo;

Has anyone else had trouble with this? Any ideas?