Rmi and EJB

Hi guys,
i feel ejb is internally using rmi.Am i right?what are the differences between rmi and ejb and also what r the similarities?
Thanks
Regards
Vivek.S

RMI is just an API that allows Java classes to be invoked remotely. It uses Java Remote Method Protocol. But it also can use IIOP in which case this whole thing is called RMI-IIOP.
RMI doesnt provide any component model like EJB, that has several types of components with well defined behavior and purpose.
Since EJB's can be called remotely they may use JRMP but it's not mandatory.
EJB's have to use IIOP as a connection protocol to ensure interoperability among EJB servers and CORBA ORB's. So EJB' s use RMI as an API, but they have to support IIOP and optionally some other protocols like JRMP. For example, WebLogic supports some interesting protocol called T3.
best regards,
Maris Orbidans
SCJP SCWCD SCBCD

Similar Messages

Difference between RMI and Java Beans

Hello
I have to develop a program that allow the users to have access to the Patient information . The program will also organize appointment between the users and the patients. + extra thing like agenda .....
I will have about 10 to 20 user that will have access at the same time to the same info .
My question is :what is the best solution for such kind of programes
RMI :after searching in google (it is light weight )
java beans:more powerful than RMI
or maybe thread ???
any one can explain the difference please ?
Thank you

A little [url http://www.google.ca/search?hl=en&q=rmi+ejb&btnG=Google+Search&meta=]google with keywords: rmi ejb would give all the answers you need.
Specifically you could read [url http://www.devx.com/Java/Article/20843/0/page/1]the article from the first result: EJB and RMI: A Practical Introduction.
Also there are many threads from these forums that already answered your question in the past.
Here is one: [url http://forum.java.sun.com/thread.jspa?threadID=539544&messageID=2613399]Rmi and EJB.
Happy reading!
Regards

Java.rmi.RemoteException: EJB Exception: while calling an EJB method,

Hi
I am getting below error while calling a stateless EJB method. There is some validation checks while performing ejb's modify() method and a RuntimeException is thrown in case of validation failure.The modify() method internally calls other stateless ejb as well.
The problem I'm facing is, instead of getting the expected RuntimeException in the Servlet, i am getting RemoteException. I am using WLS 9 MP1, all participating ejbs are stateless and i am using default transaction attributes(Supports) for these ejbs.
The interesting part is, at the ejb layer RuntimeException is thrown as expected, but this exception changed to RemoteException at the servlet's end where i am catching the ejb call exceptions.
I am new to WLS, please suggest/help me out of this exception.
Any help is truly appreciated.
java.rmi.RemoteException: EJB Exception: ; nested exception is: java.lang.RuntimeException:
     at weblogic.ejb.container.internal.EJBRuntimeUtils.throwRemoteException(EJBRuntimeUtils.java:95)
     at weblogic.ejb.container.internal.BaseEJBObject.handleSystemException(BaseEJBObject.java:713)
     at weblogic.ejb.container.internal.BaseEJBObject.handleSystemException(BaseEJBObject.java:681)
     at weblogic.ejb.container.internal.BaseEJBObject.postInvoke1(BaseEJBObject.java:447)
     at weblogic.ejb.container.internal.StatelessEJBObject.postInvoke1(StatelessEJBObject.java:72)
     at weblogic.ejb.container.internal.BaseEJBObject.postInvokeTxRetry(BaseEJBObject.java:374)
     at com.mycomp.base.BaseController_8x2e52_EOImpl.modify(BaseController_8x2e52_EOImpl.java:149)
     at com.mycomp.webgui.servlet.FrontComponent.service(FrontComponent.java:207)
     at javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
     at weblogic.servlet.internal.StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:223)
     at weblogic.servlet.internal.StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125)
     at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:283)
     at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:175)
     at weblogic.servlet.internal.WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3245)
     at weblogic.security.acl.internal.AuthenticatedSubject.doAs(AuthenticatedSubject.java:321)
     at weblogic.security.service.SecurityManager.runAs(SecurityManager.java:121)
     at weblogic.servlet.internal.WebAppServletContext.securedExecute(WebAppServletContext.java:2003)
     at weblogic.servlet.internal.WebAppServletContext.execute(WebAppServletContext.java:1909)
     at weblogic.servlet.internal.ServletRequestImpl.run(ServletRequestImpl.java:1359)
     at weblogic.work.ExecuteThread.execute(ExecuteThread.java:209)
     at weblogic.work.ExecuteThread.run(ExecuteThread.java:181)
Thanks!
Edited by: user10721298 on Feb 23, 2009 4:16 AM

Hi,
If i don't misunderstand, you are using the RuntimeException as an application exception, right?
Have you annotated it or denoted it in deployment descriptor?
Thanks,
Amy

OC4J EJBQL and EJB 2.0 features

Hello Debu Panda and All
I've got all howtos and I mangaged to get some parts of OC4J [Oracle9iAS (9.0.3.0.0) Containers for J2EE (build 020323.1689)] working.
There are still some issues that are stalling our development. Could you please comment on them, maybe providing an estimate of when they will be solved/implemented?
First of all, a little background. Our application uses many Java Swing application clients that connect to the EAR application in the container.
The ear application has the following structure:
All database access (Oracle 8i, located in its own server) is done exclusively by means of CMP entity beans. A entity bean may access other entity beans. There are workflow session beans (stateful and stateless) that access the entity beans. All clients see only the workflow session beans (session beans fagade).
Our applicatoin is complex, having more than 80 session beans and more than 25 entity beans (not counting entity beans that exist only to represent relationships among entity beans).
There goes the questions:
1) It seems that entity beans cannot currently be referenced by remote interfaces. We couldn't deploy our application using it. Since we could use only local interfaces fot entity beans, thats what is been done now.
2) There is no CMR supported. Is this true?
3) EJBQL seems to be very limited. In the howto examples there are EJBQL statements that compare two numbers. However, when we tried to use String comparisons, it didn't work. Here is the statement:
"SELECT DISTINCT OBJECT(p) FROM Person p WHERE p.name = ?1"
If I compile, package and deploy the ear applicatin with the above EJBQL statement, OC4J generates an exception when executing the finder method. The exception is:
"java.rmi.NoSuchObjectException: Session has timed out
at com.evermind.server.ejb.StatefulSessionEJBObject.throwPassivisat
ception(StatefulSessionEJBObject.java:188)
at Cad023Remote_StatefulSessionBeanWrapper0.obterPessoasPorParteNom
023Remote_StatefulSessionBeanWrapper0.java:754)
at java.lang.reflect.Method.invoke(Native Method)
at com.evermind.server.rmi.RMICallHandler.run(RMICallHandler.java:8
at com.evermind.util.ThreadPoolThread.run(ThreadPoolThread.java:64)"
If I remove the where clause, the expection is gone. However, I get all records. ;-)
4) It seems that all EJBQL clauses must be capitalized. Is this true?
FINALY)
Is there a newer OC4J build that could use to get the development going? Do you know where there will be one? Is there any way of contacting the OC4J development team to report bugs?
If you would like, we could discuss it in private e-mail (please use my private mail [email protected]).
Thanks for your attention,
Luis Fernando Soeiro
Hi !! OC4J 9.0.3 developer's preview has most features of EJB 2.0. We are working on updating on our docs and samples for EJB 2.0
Please look at the following URL that has some How Tos on EJB 2.0 features such Local Interfacea, EJB QL, etc : http://otn.oracle.com/tech/java/oc4j/htdocs/oc4j-how-to.html#ejb
regards
Debu Panda
Oracle --------------------------
Luis Soeiro <mailto:[email protected]> <mailto:[email protected]>Type : Question Date : Apr 11, 2002 15:15 PT Hello
Some colleagues and I are trying to port a large project from JBOSS to OC4J. We used JBOSS 3.0 (beta) in order to evaluate EJB2.0 features and see if we could use it. We already have OC4J in production, but only as a JSP/Servlet container. The next step would be to deploy our EJB application to OC4J.
We have read the material and it is written that OC4J (developers preview) is EJB 2.0 compliant. However, the specific documentation and the examples don't show how to specify OC4J specifc XML files. We absolutely need CMR and Local Interfaces, because we don't have the time required to downgrade our JBoss EJB2.0 application to the EJB 1.1 specification. We have over 80 Session Beans and over 20 Entity Beans.
Is there anybody there that can confirm that OC4J developer's preview is really EJB2.0 compliant? If so, could you send me some pointers to information about OC4J container specifc deployment descriptors? The docs listed at the web site don't have EJB2.0 features listed, nor does the Oracle samples.
Thanks for your attention,
desperately,
Luis Fernando Soeiro

HI,
I worked out CMR and EJB-QL with single bean.
Using CMR, it is possible to get one bean reference through other bean, but
When I tried EJB-QL with bean to bean navigation then I run into problem.

Load-balancing and fail-over between web containers and EJB containers

When web components and EJB components are run in different OC4J instances, can we achieve load-balancing and fail-over between web containers and EJB containers?
null

It looks like there is clustering, but not loadbalancing available for rmi
from the rmi.xml configuration. The application will treat any ejbs on the
cluster as one-to-one look-ups. Orion will go out and get the first ejb
available on the cluster. See the docs on configuring rmi.xml (and also the
note below).
That is a kind-of failover, because if machine A goes down, and the
myotherAejbs.jar are on machine B too, orion will go out and get the bean
from machine B when it can't find machine A. But it doesn't go machine A
then machine B for each remote instance of the bean. You could also specify
the maximum number of instances of a bean, and as one machine gets "loaded",
orion would go to the next available machine...but that's not really
loadbalancing.
That is, you can set up your web-apps with ejbs, but let all of the ejbs be
remote="true" in the orion-application.xml file:
<?xml version="1.0"?>
<!DOCTYPE orion-application PUBLIC "-//Evermind//DTD J2EE Application
runtime 1.2//EN" "http://www.orionserver.com/dtds/orion-application.dtd">
<orion-application deployment-version="1.5.2">
<ejb-module remote="true" path="myotherAejbs.jar" />
<ejb-module remote="true" path="myotherBejbs.jar" />
<ejb-module remote="true" path="myotherCejbs.jar" />
&ltweb-module id="mysite" path="mysite.war" />
... other stuff ...
</orion-application>In the rmi.xml you would define your clustering:
<cluster host="230.0.0.1" id="123" password="123abc" port="9127"
username="cluster-user" />
Tag that is defined if the application is to be clustered. Used to set up
a local multicast cluster. A username and password used for the servers to
intercommunicate also needs to be specified.
host - The multicast host/ip to transmit and receive cluster data on. The
default is 230.0.0.1.
id - The id (number) of this cluster node to identify itself with in the
cluster. The default is based on local machine IP.
password - The password configured for cluster access. Needs to match that
of the other nodes in the cluster.
port - The port to transmit and receive cluster data on. The default is
9127.
username - The username configured for cluster access. Needs to match that
of the other nodes in the cluster.

Servlet jndi lookup to remote EJB, servlet and EJB not in the same application

Hi,
I think that the subject explain my problem.
I have Oracle IAS9i 9.0.2.0.0, and JDeveloper 9.0.2.829
I have deployed and EJB in IAS9i and i want to use from the developer machines, which have JDeveloper.
how can i to do remote calls from JDeveloper?.
I have modifed the orion-application.xml, and added remote=true.
I have modifed the rmi.xml and added the hosts where the Jdeveloper placed.
Any ideas?
Thanks and cheers
P.D The app server and jdeveloper are in the same net.
if it is posible replys me to [email protected] too.

Steps to access a remote EJB from within OC4J
++++++++++++++++++++++++++++++++++++++++++++++
1) Deploy EJB application (ApplicationRemote) to remote container (REMOTE)
"java -jar admin.jar -deploy ormi://REMOTE.hostname:REMOTE.port REMOTE.username REMOTE.password -deploy -file ApplicationRemote.ear
-deploymentName ApplicationRemote"
2) Ensure that local application (ApplicationLocal) has ejb-ref tags for remote EJBs accessed (in web.xml or ejb-jar.xml)
3) Deploy to local container (LOCAL) an empty application (ApplicationEmpty) with the same name as the remote application (ApplicationRemote)
"java -jar admin.jar -deploy ormi://LOCAL.hostname:LOCAL.port LOCAL.username LOCAL.password -deploy -file ApplicationEmpty.ear -deploymentName
ApplicationRemote"
5) Deploy local application (ApplicationLocal) to local container (LOCAL)
"java -jar admin.jar -deploy ormi://LOCAL.hostname:LOCAL.port LOCAL.username LOCAL.password -deploy -file ApplicationLocal.ear -deploymentName
ApplicationLocal"
4)Restart local container
ApplicationEmpty should consist of just an application.xml file - no modules. The same file can be deployed with different application names for all the remote
applications that must be accessed.
ApplicationLocal should access the remote EJB by using the following JNDI properties
java.naming.factory.initial = "com.evermind.server.rmi.RMIInitialContextFactory"
java.naming.provider.url = "ormi://REMOTE.hostname:REMOTE.port/ApplicationRemote"
java.naming.security.principal = "REMOTE.username"
java.naming.security.credentials = "REMOTE.password"
regards
Debu Panda

Java.rmi.RemoteException: EJB Exception: ; nested exception is:

Hi All,
Please some out help me out,
i have a written a stateless session bean, which is compiled with out errors, and i deployed it in wblogic server.
when i run my client program, i get this exceptions. please some one help me how to tackle this,
Thanks in advance,
java.rmi.RemoteException: EJB Exception: ; nested exception is:
java.lang.NoClassDefFoundError: secure/SDK/SAPIAgent
Start server side stack trace:
java.rmi.RemoteException: EJB Exception: ; nested exception is:
java.lang.NoClassDefFoundError: SDK/SAPIAgent
java.lang.NoClassDefFoundError: SDK/SAPIAgent
at SAPI.SAPIBean.<init>(SAPIBean.java:18)
at SAPI.SAPIBean_163r2w_Impl.<init>(SAPIBean_163r2w_Impl.java:31)
at java.lang.Class.newInstance0(Native Method)
at java.lang.Class.newInstance(Class.java:232)
at weblogic.ejb20.manager.BaseEJBManager.allocateBean(BaseEJBManager.java:129)
at weblogic.ejb20.manager.StatelessManager.createBean(StatelessManager.java:266)
at weblogic.ejb20.pool.StatelessSessionPool.createBean(StatelessSessionPool.java:148)
at weblogic.ejb20.pool.StatelessSessionPool.getBean(StatelessSessionPool.java:101)
at weblogic.ejb20.manager.StatelessManager.preInvoke(StatelessManager.java:142)
at weblogic.ejb20.internal.BaseEJBObject.preInvoke(BaseEJBObject.java:138)
at weblogic.ejb20.internal.StatelessEJBObject.preInvoke(StatelessEJBObject.java:70)
at valyd.SAPI.SAPIBean_163r2w_EOImpl.getSession(SAPIBean_163r2w_EOImpl.java:234)
at valyd.SAPI.SAPIBean_163r2w_EOImpl_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:455)
at weblogic.rmi.cluster.ReplicaAwareServerRef.invoke(ReplicaAwareServerRef.java:114)
at weblogic.rmi.internal.BasicServerRef$1.run(BasicServerRef.java:396)
at weblogic.security.service.SecurityServiceManager.runAs(SecurityServiceManager.java:731)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:391)
at weblogic.rmi.internal.BasicExecuteRequest.execute(BasicExecuteRequest.java:30)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:261)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:223)
End server side stack trace
; nested exception is: java.lang.NoClassDefFoundError: SDK/SAPIAgent
Murali

Hi All,
Please some out help me out,
i have a written a stateless session bean, which is compiled with out errors, and i deployed it in wblogic server.
when i run my client program, i get this exceptions. please some one help me how to tackle this,
Thanks in advance,
java.rmi.RemoteException: EJB Exception: ; nested exception is:
java.lang.NoClassDefFoundError: secure/SDK/SAPIAgent
Start server side stack trace:
java.rmi.RemoteException: EJB Exception: ; nested exception is:
java.lang.NoClassDefFoundError: SDK/SAPIAgent
java.lang.NoClassDefFoundError: SDK/SAPIAgent
at SAPI.SAPIBean.<init>(SAPIBean.java:18)
at SAPI.SAPIBean_163r2w_Impl.<init>(SAPIBean_163r2w_Impl.java:31)
at java.lang.Class.newInstance0(Native Method)
at java.lang.Class.newInstance(Class.java:232)
at weblogic.ejb20.manager.BaseEJBManager.allocateBean(BaseEJBManager.java:129)
at weblogic.ejb20.manager.StatelessManager.createBean(StatelessManager.java:266)
at weblogic.ejb20.pool.StatelessSessionPool.createBean(StatelessSessionPool.java:148)
at weblogic.ejb20.pool.StatelessSessionPool.getBean(StatelessSessionPool.java:101)
at weblogic.ejb20.manager.StatelessManager.preInvoke(StatelessManager.java:142)
at weblogic.ejb20.internal.BaseEJBObject.preInvoke(BaseEJBObject.java:138)
at weblogic.ejb20.internal.StatelessEJBObject.preInvoke(StatelessEJBObject.java:70)
at valyd.SAPI.SAPIBean_163r2w_EOImpl.getSession(SAPIBean_163r2w_EOImpl.java:234)
at valyd.SAPI.SAPIBean_163r2w_EOImpl_WLSkel.invoke(Unknown Source)
at weblogic.rmi.internal.BasicServerRef.invoke(BasicServerRef.java:455)
at weblogic.rmi.cluster.ReplicaAwareServerRef.invoke(ReplicaAwareServerRef.java:114)
at weblogic.rmi.internal.BasicServerRef$1.run(BasicServerRef.java:396)
at weblogic.security.service.SecurityServiceManager.runAs(SecurityServiceManager.java:731)
at weblogic.rmi.internal.BasicServerRef.handleRequest(BasicServerRef.java:391)
at weblogic.rmi.internal.BasicExecuteRequest.execute(BasicExecuteRequest.java:30)
at weblogic.kernel.ExecuteThread.execute(ExecuteThread.java:261)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:223)
End server side stack trace
; nested exception is: java.lang.NoClassDefFoundError: SDK/SAPIAgent
Murali

Does ATS load testing support Java RMI and T3 protocol?

Hi Experts,
Does ATS load testing support Java RMI and T3 protocol or EJB(J2EE)?
Thanks!

Joseph,
Oracle Application Testing Suite is mainly used for testing of applications from a end user perspective and offers an intuitive capture/replay for web, Siebel, EBS, JDE, Fusion apps or SOA based application through WebServices WSDL imports.
The scripting environment (Oracle OpenScript) does not support script creation by recording JAVA RBI or T3 protocol as we lack a recorder for it, but the scrips are created as pure JAVA code so you could use the JAVA language to write a small RMI cor T3 client for your testing.
We have customers that have used Application Testing Suite to test non-UI based testing, like: JMS, FTP, Tuxedo and others, but it require a bit of coding.
Please let me know if you would like to know more or discuss your options
regards
Mikael Fries
Principal Product Manager / Oracle

Servlet and EJB on different machine: Security propagation

Hi all,
I have an application, where my servlets and EJBS are deployed on the same machine.So
when in my servlet a user need to authenticate himself, security credentials are
propagated to the EJB automatically.I'd like to know in the case where the components
are on different machine if I need to put the credential in my InitialContext
when my servlet calls my EJB or if it is also done automatically.
Cheers
romain

Say your stub is in a jar called stub.jar.
You need to put that stub somewhere that it can be reached through a protocol for which Java has a URL type - so you can put it on a shared file system and use a file URL or behind an http server and use an http URL.
Let's use http - put stub.jar at the docroot of a web server.
Then, when you start your SERVER code, include this VM parameter:
-Djava.rmi.server.codebase="http://<serveraddress>stub.jar"
Now your client will be able to use http to load the stub file out of stub.jar through http.
If you do use a file URL, make sure the shared directory you put your jar in is not on the client's classpath.

Spring and EJB ClassNotFound Errors

Hi,
We are migrating our application from Oracle AS 10.1.3.3 to Weblogic Server 11g. I was unable to run business layer neither via JDeveloper nor by direct deployment to server (EJB 2.1+Spring 2.5+Hibernate3) .
Spring fails to load classes although jars are there. I can use any class outside Spring but Spring just can't find any. I tried putting jars in META-INF/lib, domain/lib, even put jars in startup script of weblogic.
I am working on it for days and really need help on this. Thanks in advance.
Burak
Here is the error I get.
java.rmi.RemoteException: EJB Exception: ; nested exception is:
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'baseManager' defined in class path resource [applicationContext.xml]: Cannot create inner bean 'com.arcelik.absi.bl.base.BaseManager#c3d2e5' of type [com.arcelik.absi.bl.base.BaseManager] while setting bean property 'target'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'com.arcelik.absi.bl.base.BaseManager#c3d2e5' defined in class path resource [applicationContext.xml]: Cannot resolve reference to bean 'methodCache' while setting bean property 'cache'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'methodCache' defined in class path resource [cacheRules.xml]: Instantiation of bean failed; nested exception is org.springframework.beans.BeanInstantiationException: Could not instantiate bean class [org.springframework.cache.ehcache.EhCacheFactoryBean]: Constructor threw exception; nested exception is java.lang.NoClassDefFoundError: net/sf/ehcache/store/MemoryStoreEvictionPolicy
java.lang.NoClassDefFoundError: net/sf/ehcache/store/MemoryStoreEvictionPolicy

Hi,
Actually it is bundled in EAR file. But I already tried putting it in servers lib folder. Also added ehcache.jar in web logic as a shared library. Any other place that I can try?

Applets and EJBs

Hi:
we have a jDK 1.1.8 version Applet that needs direct access to a EJB 1.1 version ( Direct access i mean: No servlet in Between applet and EJB). The tool we are using to deploy the EJB to the Applicaton Server 3.6 ( Sybase) is PowerJ 3.6.1.
The Problem is the applet can access the EJB whenever we run the applet through Appletviewer BUT we get an Intial Context Failure error and subsequently everything related with the Bean functionality fails, when applet is run through a browser ( IE version 5.0 / 5.5 / 6.0)
Note: The applet's webserver and the Application server are on the same machine.
Can anyone help on this case.
Thank you.
Satish

Hi paul:
Thanks for your reply.
For ur question about using Applest.getCodeBase to construct the URL that you are using for your context provider,
We use the PowerJ tool to add the intial context and home interface of the EJB to the Applet application.
I am in a way restricted with this tool. The applet has been developed through this tool and the tool doesnot allow any manual changes to the Intial Context code and the Codebase that it generates.
I was going through many other forums , some say that Microsoft's ( IE / JVM ) doesnot support rmi stuff.
Do u think i should make sure that the applet has the rmi files in its classpath because when i look at the stacktrace of the applet , it gives
root execption: java.rmi.naming.* not found and subsequently Initial context fails.

Diff b/w bc4j model and ejb model in adf11g

hi all,
iam murali iam new for adf 11g i have some dout's in adf11g ,can u please solve my probleam
what is the difference b/w bc4j componet and ejb componet,how to develop ejb application in adf11g.

,how to develop ejb application in adf11gTake a look at this tutorial for starters:
http://st-curriculum.oracle.com/obe/jdev/obe11jdev/ps1/ejb/ejb.html

What is the difference between RMI and JAX-RPC?

Dear All
First of all my understanding of RMI and JAX-RPC:
RMI is JAVA only version of RPC. It can't talk to any other language.
JAX-RPC is a part of JWSDP and if you implement your client and server with JAX-RPC, client written in any language can talk with JAX-RPC implementation.
What else makes them different and am I right with my understanding?
Finally, I would like to develop clients which will have a java class, say httpserver.java, which will act like a http server, listens to a http port. Now, Two such client will run in two different PC and I want to call a module from one client to another which should be accessible via my httpserver.java. For that which should be my choice RMI or JAX-RPC? Can I achive it with http get-post method, as I am expecting to read some value of variables from one client to the another.
Say class A has variable a, aa, aaa and clas B has variable b, bb, bbb. Now I want to read the value of b, bb, bbb from class A. How do I do that when class B is listening to a http port with my httpserver.java class.
Lastly, say B is listening to a http port and I want to send a file to B from A. How can I do that? Remember, B didn�t ask for that. How can A send a file to B when B is listening to a http port with my httpserver.java.
With regards
Mohammed Jubaer Arif
Mobile: +61-0411215302
Personal Web: http://www.geocities.com/jubairarifctg/
Org. Web.: http://www.geocities.com/halimschamber/

simply put, RMI allows you to (semi) transparently treat remote objects as if they were local, and your distributed application can be written (more or less) like a "normal" java app. Sockets just give you a "raw" connection to work with, and you get to build up your application from that.
I hope that helped
Lee

Please help: RMI and Swing/AWT issue

Hi guys, I've been having a lot of trouble trying to get a GUI application to work with RMI. I'd appreciate any help. Here's the story:
I wrote a Java application and its GUI using Netbeans. In a nutshell, the application is about performing searches. I am now at the point where I need exterior programs to use my application's search capabilities, thus needing RMI. Such exterior programs are to call methods currently implemented in my application.
I implemented RMI, and got the client --> server communication working. However, the GUI just breaks. It starts outputting exceptions, gets delayed, doesn't update properly, some parts of it stop working.... basically hysterical behavior.
Now take a look at this line within my server class:
Naming.rebind("SearchProgram", mySearchProgram);
If I take it out, RMI obviously does not work... but the application and its GUI work flawlessly. If I put it in, the RMI calls work, but the GUI's above symptoms occur again. Among the symptoms are null pointer exceptions which all look similar, are related to "AWT-EventQueue-0", and keep ocurring. Here's just snippet of the errors outputted:
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.metal.MetalScrollBarUI.getPreferredSize(MetalScrollBarUI.java:102)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1615)
at javax.swing.JScrollBar.getMinimumSize(JScrollBar.java:704)
at javax.swing.ScrollPaneLayout.minimumLayoutSize(ScrollPaneLayout.java:624)
at java.awt.Container.minimumSize(Container.java:1598)
at java.awt.Container.getMinimumSize(Container.java:1583)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1697)
at java.awt.BorderLayout.minimumLayoutSize(BorderLayout.java:634)
at java.awt.Container.minimumSize(Container.java:1598)
at java.awt.Container.getMinimumSize(Container.java:1583)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1697)
at java.awt.BorderLayout.minimumLayoutSize(BorderLayout.java:634)
at java.awt.Container.minimumSize(Container.java:1598)
at java.awt.Container.getMinimumSize(Container.java:1583)
at javax.swing.JComponent.getMinimumSize(JComponent.java:1697)
at javax.swing.BoxLayout.checkRequests(BoxLayout.java:433)
at javax.swing.BoxLayout.layoutContainer(BoxLayout.java:375)
at java.awt.Container.layout(Container.java:1401)
at java.awt.Container.doLayout(Container.java:1390)
at java.awt.Container.validateTree(Container.java:1473)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validateTree(Container.java:1480)
at java.awt.Container.validate(Container.java:1448)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:379)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:113)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
Exception in thread "AWT-EventQueue-0" java.lang.NullPointerException
at javax.swing.plaf.basic.BasicMenuItemUI.getPreferredMenuItemSize(BasicMenuItemUI.java:400)
at javax.swing.plaf.basic.BasicMenuItemUI.getPreferredSize(BasicMenuItemUI.java:310)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1615)
at javax.swing.BoxLayout.checkRequests(BoxLayout.java:434)
at javax.swing.BoxLayout.preferredLayoutSize(BoxLayout.java:251)
at javax.swing.plaf.basic.DefaultMenuLayout.preferredLayoutSize(DefaultMenuLayout.java:38)
at java.awt.Container.preferredSize(Container.java:1558)
at java.awt.Container.getPreferredSize(Container.java:1543)
at javax.swing.JComponent.getPreferredSize(JComponent.java:1617)
at javax.swing.JRootPane$RootLayout.layoutContainer(JRootPane.java:910)
at java.awt.Container.layout(Container.java:1401)
at java.awt.Container.doLayout(Container.java:1390)
at java.awt.Container.validateTree(Container.java:1473)
at java.awt.Container.validate(Container.java:1448)
at javax.swing.RepaintManager.validateInvalidComponents(RepaintManager.java:379)
at javax.swing.SystemEventQueueUtilities$ComponentWorkRequest.run(SystemEventQueueUtilities.java:113)
at java.awt.event.InvocationEvent.dispatch(InvocationEvent.java:209)
at java.awt.EventQueue.dispatchEvent(EventQueue.java:461)
at java.awt.EventDispatchThread.pumpOneEventForHierarchy(EventDispatchThread.java:242)
at java.awt.EventDispatchThread.pumpEventsForHierarchy(EventDispatchThread.java:163)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:157)
at java.awt.EventDispatchThread.pumpEvents(EventDispatchThread.java:149)
at java.awt.EventDispatchThread.run(EventDispatchThread.java:110)
There are no complaints about anything within my code, it's all GUI related whenever I make a bind() or rebind() call.
Again, any help here would be great... cause this one's just beating me.
Thanks!

Maybe you want to change that worker thread to
not do RMI but anything else (dummy data) to see if it really is RMI, I doubt it, I think you are updating some structures that have to do with swing GUI and hence you will hang.
Just check this out.

JDBC, JMS and EJB transactions - possible problem?

Hello,
          I am using Oracle 9, Weblogic 8.1 SP 4, MyEclipse and
          XDoclet.
          In my current project I have the following piece of code
          in one of my message driven beans (code cited as pseudocode
          without unnecessary details):
          * @ejb.bean name="MyMessageProcessor"
          * display-name="Display name for a MyMessageProcessor"
          * jndi-name="ejb/MyMessageProcessor"
          * description="Bean MyMessageProcessor"
          * destination-type="javax.jms.Queue"
          * transaction-type="Container"
          * acknowledge-mode="Auto-acknowledge"
          * subscription-durability="Durable"
          * generate="false"
          * @ejb.transaction type="Required"
          public class MyMessageProcessor implements MessageDrivenBean, MessageListener {
          public void onMessage(Message msg) {
               try {
                    //obtaining connections to two different databases via JNDi
                    java.sql.Connection connOne =
                    ((DataSource)ctx.lookup("DataSourceOne")).getConnection();
                    java.sql.Connection connTwo =
                         ((DataSource)ctx.lookup("DataSourceTwo")).getConnection();
                    // performing some UPDATEs and INSERTs on connOne and connTwo
                    // calling some other methods of this bean
                    //creating the reply JMS message and sending it to another JMS queue
                    Message msgTwo = this.createReplyMessage(msg)
                    this.queueSender.send(msgTwo);
                    //commiting everything
                    this.queueSession.commit();
               } catch (Exception ex) {
               try {
                    if (this.queueSession!=null) this.queueSession.rollback();
               } catch (JMSException JMSEx) {};
               this.context.setRollbackOnly();
          Some days ago (before the final remarks from my client) there used to be only one DataSource configurated on the basis of the
          connection pool with non-XA jdbc driver. Everything worked fine
          including the transactions (if anything wrong happend not only wasn't the replymessage sent, but also no changes were written
          to database and the incomming message was thrown back to the my bean's
          queue).
          When I deployed the second DataSource I was informed by an error message, that only one non-transactional resource may
          participate in a global transaction. When I changed both datasources
          to depend on underlying datasources with transatcional (XA) jdbc drivers, everything stopped working. Even if
          EJB transaction was theoretically successfully rolledbacked, the changed were written to the database
          and the JMS message wasn't resent to the JMS queue.
          So here are my questions:
               1. How to configure connection pools to work in such situations? What JDBC drivers should I choose?
               Are there any global server configurations, which may influence this situation?
               2. Which jdbc drivers should I choose so that the container was able to rollback the database transactions
               (of course, if necessary)?
               3. Are there any JMS Queue settings, which would disable the container to send message back to the
               queue in case of setRollbackOnly()? How should be the Queue configurated?
          As I am new to the topic and the deadline for the project seems to be too close I would be grateful
          for any help.
          This message was sent to EJB list and JDBC list.
          Sincerely yours,
          Marcin Zakidalski

Hi,
          I found these information extremely useful and helpful.
          The seperate transaction for sending messages was, of course, unintentional. Thanks a lot.
          Anyway, I still have some problems. I have made some changes to the
          code cited in my previous mail. These changes included changing QueueSessions
          to non-transactional. I also set the "Honorate global transactions" to true.
          I am using XA JDBC driver. After setting "Enable local transactions" to false
          (I did it, because I assume that JDBC transactions should be part on the global
          EJB transaction) I got the following error:
          java.sql.SQLException: SQL operations are not allowed with no global transaction by default for XA drivers. If the XA
          driver supports performing SQL operations with no global transaction, explicitly allow it by setting
          "SupportsLocalTransaction" JDBC connection pool property to true. In this case, also remember to complete the local
          transaction before using the connection again for global transaction, else a XAER_OUTSIDE XAException may result. To
          complete a local transaction, you can either set auto commit to true or call Connection.commit() or Connection.rollback().
          I have also inspected the calls of methods of bean inside of onMessage() method just to check, whether
          the transactions are correctly initialized (using the weblogic.transaction.Transaction class).
          My questions are as follows:
          1. Any suggestions how to solve it? I have gone through the google answers on that problem and only
          thing I managed to realize that JDBC must start its own transaction. Is there any way to prohibit it
          from doing that? Can using setAutocommit(true/false) change the situation for better?
          2. How to encourage the JDBC driver to be a part of EJB transaction?
          3. As I have noticed each of ejb method has its own transactions (transactions have different
          Xid). Each method of the bean has "required" transaction attribute. Shouldn't it work in such
          way that if already started transaction exists it is used by the called method?
          4. The DataSources are obtained in my application via JNDI and in the destination environment I will have slight
          impact on the configuration of WebLogic. What is least problematic and most common WebLogic configuration which would
          enable JDBC driver to participate in the EJB transaction? Is it the WebLogic configuration problem or can it be
          solved programmically?
          Currently my module works quite fine when "enable local transactions" for DataSources is set to true, but this way
          I am loosing the ability to perform all actions in one transaction.
          Any suggestions / hints are more than welcomed. This message was posted to jdbc list and ejb list.
          Marcin

Rmi and EJB

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