Class A has a child list specifying an association to another class B.

Table A Table B
Id Id

Table C(Association Table with 3 columns)
AId(Id of Table A)
BId(Id of Table B)
SeqNo


When I was trying to rearrange the child list, obviously an index will be changing.

For example, the list I have orignally was

Original java and persisted list :
A1 B1 0
A1 B2 1
A1 B3 2

After rearranging the java list contains :
A1 B2 0
A1 B1 1
A2 B3 2

But when this list is getting persisted, hibernate is trying to do an update by seq no

update tablec set table Bid = B2 where Aid = A1 and SeqNo = 0

it is failing because we had set an unique index on BId which does not let hibernate to persist the same Bid if it is already persisted.

That means hibernate was trying to persist like this, that caused the failures.
A1 B2 0
A1 B2 1
A1 B3 2

Here is my hibernate mapping in classA mapping file.
<list name="assocList"
lazy="true"
access="field"
cascade="save-update"
outer-join="false"
table="tablec">
<key column="aid" not-null="true" unique="false"/>
<list-index column="seqno"/>
<composite-element class="ClassC">
<many-to-one name="ClassB" column="bid" lazy="proxy"/>
</composite-element>
</list>

Any ideas on how to resolve the issue?

Thanks for the help.

In this case it is not possible to do the change with only UPDATE sql statements, since you will always get a duplicate for the first update. Instead you have to force Hibernate to first DELETE all links and then INSERT the new elements. This can be done by de-referencing the original list. Eg. The A.getAssocList() should return a different list object than Hibernate passed to the A.setAssocList(). See http://www.hibernate.org/hib_docs/v3/re ... shotdelete

The de-referencing should only be done when you actually need it, otherwise Hibernate will delete an re-insert the elements in the list every time A is used in a transaction.

thanks for the reply. appreciate it.

There is no way that hibernate could update the seqno(index) for the given aid and bid?

Thanks a lot.

That would also generate a similar problem where Aid and SeqNo are duplicated and I guess those two columns make up the primary key (at least if you have used Hibernate's schema generation tool to create the tables).