Re: Serialization of datacontext

[bob]

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