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Posted to user@cayenne.apache.org by bob <sa...@gmail.com> on 2007/06/04 10:46:14 UTC
Re: Serialization of datacontext
Hi
I debugged this a bit and notice the following:
on DataContext serialization the following code is executed in
writeObject(ObjectOutputStream)
...
// Serialize local snapshots cache
if (!isUsingSharedSnapshotCache()) {
out.writeObject(objectStore.getDataRowCache());
}
...
So if useSharedCache is false, the ObjectStore's DataRowStore is also
serialized.
DataRowStore's reference to EventManager is transient and not
serialized. So upon deserialization, when DataRowStore is read back
in, the EventManager is null and this caused the exception below.
What is the best way to fix this? EventManager should not be
transient? Or a new EventManager should be created in
DataRowStore.readObject(ObjectInputStream)?
regards
bob
bob wrote:
> Hi all
>
> Using cayenne 1.2.3 and jdk 1.5 on Windows XP.
>
> Sometimes while developing with Tomcat I get the following exception.
> Seems to happen on serialization of DataContext along with the session.
> Below the exception is a little test class to reproduce this. Note that
> if useSharedCache = true, then there is no exception. Should I open a
> JIRA issue or is this expected behavior?
>
>
> Exception in thread "main"
> org.objectstyle.cayenne.CayenneRuntimeException: [v.1.2.3 May 6 2007]
> Commit Exception
> org.objectstyle.cayenne.access.DataContext.flushToParent(DataContext.java:1290)
>
> org.objectstyle.cayenne.access.DataContext.commitChanges(DataContext.java:1166)
>
> test.SerializeDCTest.main(SerializeDCTest.java:29)
>
> Caused by: java.lang.NullPointerException
> org.objectstyle.cayenne.access.DataRowStore.sendUpdateNotification(DataRowStore.java:709)
>
> org.objectstyle.cayenne.access.DataRowStore.processSnapshotChanges(DataRowStore.java:574)
>
> org.objectstyle.cayenne.access.DataDomainFlushAction.postprocess(DataDomainFlushAction.java:278)
>
> org.objectstyle.cayenne.access.DataDomainFlushAction.flush(DataDomainFlushAction.java:178)
>
> org.objectstyle.cayenne.access.DataDomain.onSyncFlush(DataDomain.java:846)
> org.objectstyle.cayenne.access.DataDomain$2.transform(DataDomain.java:817)
> org.objectstyle.cayenne.access.DataDomain.runInTransaction(DataDomain.java:872)
>
> org.objectstyle.cayenne.access.DataDomain.onSync(DataDomain.java:814)
> org.objectstyle.cayenne.access.DataContext.flushToParent(DataContext.java:1262)
>
>
>
> package test;
>
> public class SerializeDCTest {
>
> public SerializeDCTest() {
> }
>
> public static void main(String[] args) {
> //boolean useSharedCache = true; //works
> boolean useSharedCache = false;
> DataContext context =
> DataContext.createDataContext(useSharedCache);
> context = serializeDC(context);
> Employee emp = (Employee) DataObjectUtils.objectForPK(context,
> Employee.class, 740);
> emp.setFirstname("test" + Math.random());
> context.commitChanges();
> }
>
> public static DataContext serializeDC(DataContext dc) {
> try {
> ByteArrayOutputStream bos = new ByteArrayOutputStream();
> ObjectOutputStream oos = new ObjectOutputStream(bos);
> oos.writeObject(dc);
>
> ByteArrayInputStream is = new
> ByteArrayInputStream(bos.toByteArray());
> ObjectInputStream ois = new ObjectInputStream(is);
> DataContext result = (DataContext) ois.readObject();
> return result;
>
> } catch (Exception ex) {
> throw new RuntimeException("DataContext serialization
> failed", ex);
> }
> }
> }
>
>
> kind regards
>
> bob
>
>
Re: Serialization of datacontext
Posted by Andrus Adamchik <an...@objectstyle.org>.
Could you please open a bug report? We'll need to do some testing to
settle on the best strategy (I am leaning towards not serializing the
local DataRowStore at all, and rebuilding it on deserialization
instead).
Thanks
Andrus
On Jun 4, 2007, at 11:46 AM, bob wrote:
> Hi
>
> I debugged this a bit and notice the following:
>
> on DataContext serialization the following code is executed in
> writeObject(ObjectOutputStream)
>
> ...
> // Serialize local snapshots cache
> if (!isUsingSharedSnapshotCache()) {
> out.writeObject(objectStore.getDataRowCache());
> }
> ...
>
> So if useSharedCache is false, the ObjectStore's DataRowStore is
> also serialized.
>
> DataRowStore's reference to EventManager is transient and not
> serialized. So upon deserialization, when DataRowStore is read back
> in, the EventManager is null and this caused the exception below.
>
> What is the best way to fix this? EventManager should not be
> transient? Or a new EventManager should be created in
> DataRowStore.readObject(ObjectInputStream)?
>
> regards
>
> bob
>
> bob wrote:
>> Hi all
>> Using cayenne 1.2.3 and jdk 1.5 on Windows XP.
>> Sometimes while developing with Tomcat I get the following
>> exception. Seems to happen on serialization of DataContext along
>> with the session. Below the exception is a little test class to
>> reproduce this. Note that if useSharedCache = true, then there is
>> no exception. Should I open a JIRA issue or is this expected
>> behavior?
>> Exception in thread "main"
>> org.objectstyle.cayenne.CayenneRuntimeException: [v.1.2.3 May 6
>> 2007] Commit Exception
>> org.objectstyle.cayenne.access.DataContext.flushToParent
>> (DataContext.java:1290)
>> org.objectstyle.cayenne.access.DataContext.commitChanges
>> (DataContext.java:1166) test.SerializeDCTest.main
>> (SerializeDCTest.java:29)
>> Caused by: java.lang.NullPointerException
>> org.objectstyle.cayenne.access.DataRowStore.sendUpdateNotification
>> (DataRowStore.java:709)
>> org.objectstyle.cayenne.access.DataRowStore.processSnapshotChanges
>> (DataRowStore.java:574)
>> org.objectstyle.cayenne.access.DataDomainFlushAction.postprocess
>> (DataDomainFlushAction.java:278)
>> org.objectstyle.cayenne.access.DataDomainFlushAction.flush
>> (DataDomainFlushAction.java:178)
>> org.objectstyle.cayenne.access.DataDomain.onSyncFlush
>> (DataDomain.java:846)
>> org.objectstyle.cayenne.access.DataDomain$2.transform
>> (DataDomain.java:817)
>> org.objectstyle.cayenne.access.DataDomain.runInTransaction
>> (DataDomain.java:872)
>> org.objectstyle.cayenne.access.DataDomain.onSync(DataDomain.java:814)
>> org.objectstyle.cayenne.access.DataContext.flushToParent
>> (DataContext.java:1262) package test;
>> public class SerializeDCTest {
>> public SerializeDCTest() {
>> }
>> public static void main(String[] args) {
>> //boolean useSharedCache = true; //works
>> boolean useSharedCache = false;
>> DataContext context = DataContext.createDataContext
>> (useSharedCache);
>> context = serializeDC(context);
>> Employee emp = (Employee) DataObjectUtils.objectForPK
>> (context, Employee.class, 740);
>> emp.setFirstname("test" + Math.random());
>> context.commitChanges();
>> }
>> public static DataContext serializeDC(DataContext dc) {
>> try {
>> ByteArrayOutputStream bos = new ByteArrayOutputStream();
>> ObjectOutputStream oos = new ObjectOutputStream(bos);
>> oos.writeObject(dc);
>> ByteArrayInputStream is = new ByteArrayInputStream
>> (bos.toByteArray());
>> ObjectInputStream ois = new ObjectInputStream(is);
>> DataContext result = (DataContext) ois.readObject();
>> return result;
>> } catch (Exception ex) {
>> throw new RuntimeException("DataContext serialization
>> failed", ex);
>> }
>> }
>> }
>> kind regards
>> bob
>
>