NullPointerException in ContextCommit with locking due to no retained snapshot on unset to-one relationship

From: Mike Kienenberger (mkienen..mail.com)
Date: Thu Mar 27 2008 - 15:32:52 EDT

  • Next message: Mike Kienenberger: "Re: NullPointerException in ContextCommit with locking due to no retained snapshot on unset to-one relationship"

    Here's an interesting situation I'm debugging now for Cayenne 1.1.
    It seems to be related to CAY-213 "NullPointerException in
    ContextCommit with locking". I suspect that it's true of 1.2 and
    could very well be true for 3.0 as well, although I don't have that
    handy to test with.

    http://issues.apache.org/cayenne/browse/CAY-213

    My testing seems to reveal that the same problem occurs when you set a
    to-one relationship to null. Line 291 in removeToManyTarget() sets
    the state of the previous to-one relationship object to MODIFIED, but
    doesn't retain a snapshot for that object.

    Here's some simple test code that shows the problem. And switching
    the scalar setter with the relationship setter works around the
    problem.

    It seems to me that the the fix is to add

                dataContext.getObjectStore().retainSnapshot(this);

    as was done for writeProperty().

        public void run() throws Exception
        {
            initCayenne("cayenne.xml");

            // Set up database
            createSchemaForObjEntityName(Configuration.getSharedConfiguration(),
    "PotentialCustomer");
            DataContext dc = DataContext.createDataContext();

            // Set up test data
            PotentialCustomer pc =
    (PotentialCustomer)dc.createAndRegisterNewObject(PotentialCustomer.class);
            Premise premise = (Premise)dc.createAndRegisterNewObject(Premise.class);
            pc.setToOneTarget("premise", premise, true);
            dc.commitChanges();

            // Force failure:
            pc.setToOneTarget("premise", null, true);
            premise.writeProperty("altitude", new Integer(0));

    // On commitChanges(), no snapshot available for building locking
    // java.lang.NullPointerException
    // at org.objectstyle.cayenne.access.ContextCommit.appendOptimisticLockingAttributes(ContextCommit.java:564)

            dc.commitChanges();
        }

    java.lang.NullPointerException
            at org.objectstyle.cayenne.access.ContextCommit.appendOptimisticLockingAttributes(ContextCommit.java:564)
            at org.objectstyle.cayenne.access.ContextCommit.prepareUpdateQueries(ContextCommit.java:426)
            at org.objectstyle.cayenne.access.ContextCommit.commit(ContextCommit.java:156)
            at org.objectstyle.cayenne.access.DataContext.commitChanges(DataContext.java:1266)
            at org.objectstyle.cayenne.access.DataContext.commitChanges(DataContext.java:1236)
            at com.gvea.cayenne.TestOptimisticLockingFailureOnSingleTargetNull.run(TestOptimisticLockingFailureOnSingleTargetNull.java:110)
            at com.gvea.cayenne.TestOptimisticLockingFailureOnSingleTargetNull.main(TestOptimisticLockingFailureOnSingleTargetNull.java:24)

    Note that some of these line numbers may vary as my version of Cayenne
    1.1 has local mods.

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