Caching & thread in ejb

Hi,
In order to gain better performance in our current application
we need to cache some data in both web and ejb tier. Data that
we need to store is not client specific (global data) and rarely
changes. In web tier we cache this kind of data in
ServletContext. We are trying to find a way to store data in ejb
tier. In our design we use only Stateless Session Beans in which
we have JDBC calls to access DB. In particular case we need to
get some data from DB that is specific to current date. So,
ideally we would like to fetch that data when ejb server starts,
store it and refresh it at midnight. So, if this was not an ejb
application we would probably use Singleton to store this data
and have some thread that will wake up at 0:00 to refresh
state of the singleton object.
I would really appreciate any suggestion.
Regards,
Ilija

Making it ReadOnly will ensure that ejbLoad is not called. Also,
if you use 6.1, generated home implements weblogic.ejb.Caching[Local]Home,
which makes invalidations (local and in cluster) easier.
Ilija <[email protected]> wrote:
Thanks. I have few more questions regarding caching. I am not
sure if what I am doing is completely correct.I have entity ejb
with bean managed persistence that caches data. Data is
retrieved from multiple tables and there is no real bean dentity
in DB.
ejbFindByPrimaryKey does not go to DB, it simply returns passes String value(primary
key).
ejbLoad() loads everything from DB and initialize instance of
the bean.
ejbRemove() does not do anything.
ejbStore() does not do anything.
ejbActivate() does not do anything
ejbPasivate does not do anything
invalidate() throws RemoteException
baean is deployed with NotSupported transaction attribute.
Everything seems to be working OK. I am wandering if there is any
benefits of making this bean as a read only since ejbStore does
not do anything in my case.
Dimitri Rakitine <[email protected]> wrote:
That's what I did - I wrote my own implementation of JMX timer.
Anyway, this deprecation of time services is a little confusing. I saw
2 replacement recommendations in WebLogic docs (both unacceptable) -
use
java.util.Timer, or purchase Flux.
On the other hand, time services work just fine in 6.1.
Ilija <[email protected]> wrote:
Thanks Dimitri. I see that weblogic deprecated api for trigger andI am curios
if it would be correct to have my own scheduler in web tier that willinvalidate
this ejb.
Dimitri Rakitine <[email protected]> wrote:
Schedule a trigger which will invalidate RO bean(s) at midnight ?
Ilija <[email protected]> wrote:
Thank you for your suggestions Rob. I guess read only entity beansare very close
to what we need. The only issue I can see is the fact that we haveto update state
of this bean at midnight. Since we are not supposed to create threadin ejb container
what do you suggest as a way to do that?
Regards,
Ilija
Rob Woollen <[email protected]> wrote:
Ilija wrote:
Hi,
In order to gain better performance in our current application
we need to cache some data in both web and ejb tier. Data that
we need to store is not client specific (global data) and rarely
changes. In web tier we cache this kind of data in
ServletContext.I would suggest that you use the JSP Cache tags and Cache filters
in
WLS for caching in the web tier. They will allow you to cache pages
or
page fragments.
We are trying to find a way to store data in ejb
tier. In our design we use only Stateless Session Beans in which
we have JDBC calls to access DB. In particular case we need to
get some data from DB that is specific to current date. So,
ideally we would like to fetch that data when ejb server starts,
store it and refresh it at midnight. So, if this was not an ejb
application we would probably use Singleton to store this data
and have some thread that will wake up at 0:00 to refresh
state of the singleton object.
Take a look at Read-Only entity beans.
-- Rob
I would really appreciate any suggestion.
Regards,
Ilija
Dimitri--
Dimitri
Dimitri

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I also crossposted to EJB forum -> http://forum.java.sun.com/thread.jsp?forum=13&thread=538526&tstart=0&trange=15

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Edited by: punkouterz on Oct 15, 2007 5:08 PM
Moved to a more appropriate forum : http://forum.java.sun.com/thread.jspa?threadID=5226379

I'm pretty new with EJB and I'm trying to architect a simple application using it. I'm using an Application Server that potentially may span into multiple servers with clustering. I'm building my business layer using EJB so that the AS can handle server clustering automatically. The EJB objects actually only serves as a facade to my DAL using TDG and DTO objects. I can get this setup to work, however it come across to my mind that I might have a problem with multiple clustering servers when I'm building my own caching scheme for my DTO objects. The problem is because in the scenario with multiple servers, the cache object may live (/span) to multiple servers also. Now, if I use POJO to build the cache, (I'm only assuming here) then theres a possibility that my cache will be used on multiple instances on multiple servers. If I store a DTO object on one of my cache on a specific server then when a client request that object and the request accidentally routed through another server, then the caching system wont recognize the DTO object cached in another server and would try to retrieve the object from DB and put it in the cache specific to that server. That would cause my caching system fails and, worse, I'd have multiple copies of the same object which, of course, will be disastrous.
I havent really figured out how to overcome this problem, maybe building my cache object using EJB also could save the problem so that every request would have to be handled via JNDI, but I still couldn't figure out how will I be able to resolve if an object already instanced in another server and what about the penalty from doing such a thing. Can anyone give me guidances or suggestions or point me where I should look for informations?
Edited by: punkouterz on Oct 15, 2007 5:08 PM
Moved to a more appropriate forum : http://forum.java.sun.com/thread.jspa?threadID=5226379

ClassNotFoundException in EJB's and Threads (Classloader issue)

A very interesting bug has cropped up in WebLogic 6.1. When a J2EE
application packaged appropriately, a client application running in a
user-created Thread will always throw a ClassNotFoundException when
attempting to get back a user-created object from an EJB living on
another cluster. This error does not happen when the call is being made
from outside a Thread.
Sounds strange, I know, so I'll try to give everyone as much detail as
possible so they can avoid this bug, and so that the folks at BEA can
fix it.
* A java class running inside a clustered WL6.1 server is attempting to
reference an EJB on another clustered WL 6.1 server. Accessing the bean
is not a problem, the client class is able to obtain a remote reference
to the bean and make method calls on it. Calling a method causes the
following stack trace:
2002-01-11 10:36:57,331 [Thread-4] ERROR
wpni.app.mywp.display.DisplayJobs$JobsMonitor -
wpni.app.mywp.display.DisplayJobs$JobsMonitor.run: Error checking Jobs
status.
java.rmi.UnmarshalException: failed to unmarshal class
wpni.app.jobs.JobsData; nested exception is:
java.lang.ClassNotFoundException: wpni.app.jobs.JobsData: This
error could indicate that a component was deployed on a cluster member
but not other members of that cluster. Make sure that any component
deployed on a server that is part of a cluster is also deployed on all
other members of that cluster
java.lang.ClassNotFoundException: wpni.app.jobs.JobsData: This error
could indicate that a component was deployed on a cluster member but
not other members of that cluster. Make sure that any component deployed
on a server that is part of a cluster is also deployed on all other
members of that cluster
at
weblogic.j2ee.ApplicationManager.loadClass(ApplicationManager.java:146)
at
weblogic.rjvm.MsgAbbrevInputStream.readClassDescriptor(MsgAbbrevInputStream.java:211)
at
weblogic.common.internal.ChunkedObjectInputStream$NestedObjectInputStream.readClassDescriptor(ChunkedObjectInputStream.java:290)
at
java.io.ObjectInputStream.inputClassDescriptor(ObjectInputStream.java:906)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:366)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:236)
at
java.io.ObjectInputStream.inputObject(ObjectInputStream.java:1186)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:386)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:236)
at
weblogic.common.internal.ChunkedObjectInputStream.readObject(ChunkedObjectInputStream.java:107)
at
weblogic.common.internal.ChunkedObjectInputStream.readObject(ChunkedObjectInputStream.java:115)
at weblogic.rmi.internal.ObjectIO.readObject(ObjectIO.java:56)
at
weblogic.rmi.internal.BasicRemoteRef.unmarshalReturn(BasicRemoteRef.java:230)
at
weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:254)
at
weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:220)
at weblogic.rmi.internal.ProxyStub.invoke(ProxyStub.java:35)
at $Proxy140.getJobsData(Unknown Source)
at
wpni.app.mywp.display.DisplayJobs$JobsMonitor.run(DisplayJobs.java:48)
at java.lang.Thread.run(Thread.java:484)
* The class that is not found (JobsData) is definitely in the EAR file
on both the client cluster and the server cluster, and in the
appropriate location.
* When we attempted to run the code outside of a Thread, everything
worked perfectly, so it was definitely the Thread that was causing the
problem.
* Deploying the EJB on the client cluster did not do anything to solve
the problem.
* Adding the JobsData to the System CLASSPATH at the startup of the
WebLogic server DID solve the problem. But of course that defeats the
purpose of packaging everything in the EAR file.
So, the conclusion seems to be that when DisplayJobs$JobsMonitor kicked
off the Thread, the Thread should have been created in either the WAR's
classloader or the JAR's classloader (wouldn't matter, since the
JobsData class is in the JAR's classloader, which is a parent of the
WAR's classloader). But instead, the Thread is being created in the
System classloader, which can't find the JobsData class!
We believe that any Thread created by a class living within an EAR's
classloader should remain within that same classloader, and not migrate
to any other classloader, in order to avoid situations like this. We're
opening a case with BEA to attempt to get this resolved. In the
meantime, we recommend to developers that if they have to make
cross-cluster RMI calls from inside user-created Threads, that they only
attempt to receive primitive types or standard JDK objects. Otherwise,
you'll have to add the classes to the System CLASSPATH at startup of the
WebLogic instance.
Thanks,
Erin
* "[White House spokeperson Ari] Fleischer
* warned Democrats this morning against
* investigations into the Bush administration's
* dealings with Enron. 'The American people
* are tired of partisan witch hunts and endless
* investigations,' he said." [Ed.: Uh... ]
* www.washingtonpost.com/wp-dyn/articles/A25159-2002Jan10.html
* Erin Reid Myers, Chief Architect
* WashingtonPost.Newsweek Interactive
* [email protected]
* Work: (703) 469-3154
* Cell: (703) 725-3050
[att1.html]

Things can go seriously wrong if your application uses user threads (violating
EJB spec programming restrictions and BEA recommendations).
I'm curious, does it work if you enable network classloading on the server
which invokes remote EJB (in config.xml -
<Server NetworkClassLoadingEnabled="true" ...
</Server>
Erin Reid Myers <[email protected]> wrote:
A very interesting bug has cropped up in WebLogic 6.1. When a J2EE
application packaged appropriately, a client application running in a
user-created Thread will always throw a ClassNotFoundException when
attempting to get back a user-created object from an EJB living on
another cluster. This error does not happen when the call is being made
from outside a Thread.
Sounds strange, I know, so I'll try to give everyone as much detail as
possible so they can avoid this bug, and so that the folks at BEA can
fix it.
* A java class running inside a clustered WL6.1 server is attempting to
reference an EJB on another clustered WL 6.1 server. Accessing the bean
is not a problem, the client class is able to obtain a remote reference
to the bean and make method calls on it. Calling a method causes the
following stack trace:
2002-01-11 10:36:57,331 [Thread-4] ERROR
wpni.app.mywp.display.DisplayJobs$JobsMonitor -
wpni.app.mywp.display.DisplayJobs$JobsMonitor.run: Error checking Jobs
status.
java.rmi.UnmarshalException: failed to unmarshal class
wpni.app.jobs.JobsData; nested exception is:
java.lang.ClassNotFoundException: wpni.app.jobs.JobsData: This
error could indicate that a component was deployed on a cluster member
but not other members of that cluster. Make sure that any component
deployed on a server that is part of a cluster is also deployed on all
other members of that cluster
java.lang.ClassNotFoundException: wpni.app.jobs.JobsData: This error
could indicate that a component was deployed on a cluster member but
not other members of that cluster. Make sure that any component deployed
on a server that is part of a cluster is also deployed on all other
members of that cluster
at
weblogic.j2ee.ApplicationManager.loadClass(ApplicationManager.java:146)
at
weblogic.rjvm.MsgAbbrevInputStream.readClassDescriptor(MsgAbbrevInputStream.java:211)
at
weblogic.common.internal.ChunkedObjectInputStream$NestedObjectInputStream.readClassDescriptor(ChunkedObjectInputStream.java:290)
at
java.io.ObjectInputStream.inputClassDescriptor(ObjectInputStream.java:906)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:366)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:236)
at
java.io.ObjectInputStream.inputObject(ObjectInputStream.java:1186)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:386)
at
java.io.ObjectInputStream.readObject(ObjectInputStream.java:236)
at
weblogic.common.internal.ChunkedObjectInputStream.readObject(ChunkedObjectInputStream.java:107)
at
weblogic.common.internal.ChunkedObjectInputStream.readObject(ChunkedObjectInputStream.java:115)
at weblogic.rmi.internal.ObjectIO.readObject(ObjectIO.java:56)
at
weblogic.rmi.internal.BasicRemoteRef.unmarshalReturn(BasicRemoteRef.java:230)
at
weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:254)
at
weblogic.rmi.cluster.ReplicaAwareRemoteRef.invoke(ReplicaAwareRemoteRef.java:220)
at weblogic.rmi.internal.ProxyStub.invoke(ProxyStub.java:35)
at $Proxy140.getJobsData(Unknown Source)
at
wpni.app.mywp.display.DisplayJobs$JobsMonitor.run(DisplayJobs.java:48)
at java.lang.Thread.run(Thread.java:484)
* The class that is not found (JobsData) is definitely in the EAR file
on both the client cluster and the server cluster, and in the
appropriate location.
* When we attempted to run the code outside of a Thread, everything
worked perfectly, so it was definitely the Thread that was causing the
problem.
* Deploying the EJB on the client cluster did not do anything to solve
the problem.
* Adding the JobsData to the System CLASSPATH at the startup of the
WebLogic server DID solve the problem. But of course that defeats the
purpose of packaging everything in the EAR file.
So, the conclusion seems to be that when DisplayJobs$JobsMonitor kicked
off the Thread, the Thread should have been created in either the WAR's
classloader or the JAR's classloader (wouldn't matter, since the
JobsData class is in the JAR's classloader, which is a parent of the
WAR's classloader). But instead, the Thread is being created in the
System classloader, which can't find the JobsData class!
We believe that any Thread created by a class living within an EAR's
classloader should remain within that same classloader, and not migrate
to any other classloader, in order to avoid situations like this. We're
opening a case with BEA to attempt to get this resolved. In the
meantime, we recommend to developers that if they have to make
cross-cluster RMI calls from inside user-created Threads, that they only
attempt to receive primitive types or standard JDK objects. Otherwise,
you'll have to add the classes to the System CLASSPATH at startup of the
WebLogic instance.
Thanks,
Erin
* "[White House spokeperson Ari] Fleischer
* warned Democrats this morning against
* investigations into the Bush administration's
* dealings with Enron. 'The American people
* are tired of partisan witch hunts and endless
* investigations,' he said." [Ed.: Uh... ]
* www.washingtonpost.com/wp-dyn/articles/A25159-2002Jan10.html
* Erin Reid Myers, Chief Architect
* WashingtonPost.Newsweek Interactive
* [email protected]
* Work: (703) 469-3154
* Cell: (703) 725-3050
Dimitri

EJB Cache

Hi!
I am having trouble figuring out how to do sessions in web services. For this porpouse I would like to use a cache in an EJB container...
How could I make this cache, so that there is only one instance per cluster???

Thanks swatdba,
But I am trying to keep my app portable.
I think I am going to do a singleton.
Better to have one cache per VM rather not have any at all.

Urgent - calling EJB methods from thread

Dear all
I am aware of EJB spec that does not permit developer managed threads within EJB components. However, I need to call EJB methods from my own thread. Hence, it there any way to to call EJB methods from developer managed thread ?? If yes, please advice me, thanks in advance and your help will be appriciated.
Hava a nice day

You can call EJB's from your threads. Your thread will act as the client and the call will to EJB will be same as any other client invoking EJB's. Hope I understand your question !.

Caching on ejb container using Oracle 9i Application server

Hi,
can we cache on the ejb container in Oracle application server ?
if so, whats the methodology ?
Regards,
Murali

Can you explain exactly what you want to cache? The complete container: no makes no sences. Objects in the container, makes sences but in case of CMP the entites are already cached.
Can you provide more information what you want to achieve?

Caching & thread in ejb

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