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http://jira.jboss.com/jira/browse/JBPM-1008?page=comments#action_12376044 ]
Adrian Dimulescu commented on JBPM-1008:
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I have tried to find an easy fix to this one and failed. Getting Hibernate out of an
object tree is difficult. I think that the problem is inherent to a remote facade that
exposes a rich domain model which is the case of the CommandServiceBean bean.
When querying this service, you get rich domain object trees, with Hibernate lazy-loading
behaviour as a plus. This is ok for local ejb interfaces; I think this is not ok for
remote serialized facades. A remote facade should offer non-rich, plained-down information
like, for example, long[] getNonFinishedTaskIds() and the like. Even if cleaning
Hibernate-specific structures were possible, returning rich object trees would mean either
initializing lazy links and returning half the database or returning semantically wrong
null-values.
So I basically think the remote interface and the local interface should not be the same.
I my case I offer as much functionality as possible using a web interface which uses the
local ejb interface; for remote access, I offer a different remote facade that is
independent jBPM and which uses the jBPM ejb in order to do its stuff. For direct access
to the remote jBPM ejb, I stick to the constraints of including Hibernate among client
dependencies and never dereferencing the lazy references.
ejb deployment : avoid ClassNotFoundException on client side after
unmarshalling
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Key: JBPM-1008
URL:
http://jira.jboss.com/jira/browse/JBPM-1008
Project: JBoss jBPM
Issue Type: Bug
Affects Versions: jBPM jPDL 3.2.1
Environment: enterprise jBPM
Reporter: Adrian Dimulescu
Assigned To: Tom Baeyens
Fix For: jBPM jPDL 3.2.3
Two aspects in this jira : 1: hide hibernate-specific exceptions; 2: hide
hibernate-specific datatypes.
1. The EJB client only depends on the jBPM jar (for the various Command implementations)
and on the JBoss client jar. If a Hibernate exception occurs, it is wrapped by a
JBPMException and rethrown. When deserialiezed on the client side (which does not have a
Hibernate dependency), a ClassNotFoundException occurs.
I think the CommandServiceBean should not wrap internal implementation-specific
exceptions; it should instead simply copy the stack trace and throw a new
implementation-independent exception which contains the exception trace without containing
the causes themselves. That typically avoids ClassNotFoundExceptions without losing
exception history.
2. The second problem is that hibernate-specific collections get serialized over the
wire, here is the description of the problem :
I use the GetProcessInstancesCommand in order to experiment with querying the remote ejb.
This command returns a list with ProcessInstances. A ProcessInstance is read by Hibernate
from the database. As Hibernate uses specific lazy-loading-aware implementations for
collections -- the ProcessInstance.instances attribute, which is declared of type
java.util.Map, is actually implemented by org.hibernate.collections.PersistentMap.
Which generates class loading exception while deserializing to hibernate-unaware ejb
clients.
The solution would then be for the Command implementations to return clean JDK
collections, by replacing Hibernate collection with JDK standard ones. Note that IIUC only
the collections must be replaced, not the collection contents too, so the
"cleaning" operation should not be that expensive. Cleaning should be only done
in the SLSB remote call use case -- because in-JVM callers may want to benefit
lazy-loading.
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