I have two objects, A and B with a link table A_B. In the hbm.xml, I have the mapping as:

<class name="A" table="A">
<id name="AID" type="string" unsaved-value="null">
<column name=AID" sql-type="varchar(100)" not-null="true"/>
<generator class="uuid.hex"/>
</id>
<set name="bs" table="A_B" cascade="save-update">
<key column="AID"/>
<many-to-many column="BID" class="B"/>
</set>
</class>

<class name="B" table="B">
<id name="BID" type="string" unsaved-value="null">
<column name=BID" sql-type="varchar(100)" not-null="true"/>
<generator class="uuid.hex"/>
</id>
<set name="as" table="A_B" cascade="save-update">
<key column="BID"/>
<many-to-many column="AID" class="A"/>
</set>
</class>

My code gets an A by doing an id search and retrieves the correct A as evidenced by a printout of its ID, but the size of the bs collection in object A is 0, even though a query of the database:

Select B.BID from A_B, B where A_B.AID='1' and A_B.BID=B.BID

produces 3 results. I would expect that Hibernate would do a similar query to get the BID's, then load the B's into the Set per the mapping, but it looks like I'm missing something. I've gotten other many-to-many's to work in the past, but I can't see the difference. Any ideas on what would cause an empty collection? There are no errors. I'm not looking for anyone to debug my code here, just some thoughts on what might cause an empty collection would help me continue my debugging.

One side must be inverse="true"
check your pojo and the setter/getter correctness
check equals hashcode implementation

Inverse='true' should only affect updates, not queries, correct? I do a query in the db, and there are entries in the link table for the A='1' case, so this shouldn't be an update issue. The entries are still there after I run my code as well, so its not like Hibernate is wiping out the entries either.

Since these are just string values, I haven't touched the hashcode implementation.

I'll take a look at the setter/getter, although I am seeing this behavior on other many-many's as well, so I was assuming I had a Hibernate property messed up.

Thanks for the suggestions!