a cup of java

I don’t know whether I should call it an issue. But for me it was an issue. Recently I switched to JBoss 5.1.0 GA. But when I tried to run it, it was throwing the following exception:

[ClassLoaderManager] Unexpected error during load of:org.jboss.resource.metadata.repository.DefaultJCAMetaDataRepository
java.lang.UnsupportedClassVersionError: Bad version number in .class file
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
        at org.jboss.classloader.spi.base.BaseClassLoader.access$200(BaseClassLoader.java:63)
        at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:572)
        at org.jboss.classloader.spi.base.BaseClassLoader$2.run(BaseClassLoader.java:532)
        at java.security.AccessController.doPrivileged(Native Method)

You will have this problem if you are working with JDK 1.5.x. You can switch to JDK 1.6.x and you can get it working fine. But my entire work setup required me to run my Eclipse Ganymede on 1.5 but JBoss on 1.6. So I wrote a batch file which look like this:

@echo off
echo Overriding the Jboss home and Java home ...
set JBOSS_HOME=D:\jboss-5.1.0.GA
set JAVA_HOME=C:\Program Files\Java\jdk1.6.0
echo Jboss home: %JBOSS_HOME%
echo Java home: %JAVA_HOME%
call %JBOSS_HOME%\bin\run.bat -b 192.168.x.y

So I can have my Eclipse running on 1.5 with JBOSS_HOME set to JDK 1.5 and JBoss on 1.6. Hope this will be helpful for you in some way.

I found this small but very good article in phpied.com by Stoyan Stefanov – Twitter page. The article tells about handling broken images in a web page, especially when we dont have control over what we load in our page.

I know, you don’t have broken images on your site, it’s unprofessional and ugly. But sometimes you may be loading images that you don’t control and you never know what’s going on on the other server you’re expecting to serve, but it may not feel up to the task.

One nice and simple strategy to deal with this uncertainty is to hide the images that fail to load. Browsers sent an “error” event when the worst happens and an image fails for whatever reason. Subscribe to this event using your favorite event-listener-attaching approach or library and hide the image.

The solution is very simple.

<img src="broken.png"
  onerror="this.style.display='none'"
/>

Read the article here

Me and my colleague Venu were working on some Jboss 5 stuff  (infact migrating from Jboss 4 to 5) when we got the following exception.

Exception:

ERROR [my.package.name] doSomething() Ex: javax.naming.CommunicationException [Root exception is java.io.InvalidClassException: org.jboss.ejb3.remoting.IsLocalInterceptor; local class incompatible: stream classdesc serialVersionUID = -3758782076801249473, local class serialVersionUID = 337700910587744646]

javax.naming.CommunicationException [Root exception is java.io.InvalidClassException: org.jboss.ejb3.remoting.IsLocalInterceptor; local class incompatible: stream classdesc serialVersionUID = -3758782076801249473, local class serialVersionUID = 337700910587744646]

at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:725)
at org.jnp.interfaces.NamingContext.lookup(NamingContext.java:590)
at javax.naming.InitialContext.lookup(InitialContext.java:351)

.. .. ..

Caused by: java.io.InvalidClassException: org.jboss.ejb3.remoting.IsLocalInterceptor; local class incompatible: stream classdesc serialVersionUID = -3758782076801249473, local class serialVersionUID = 337700910587744646

at java.io.ObjectStreamClass.initNonProxy(ObjectStreamClass.java:546)
at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1552)
at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1466)
at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1699)
at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1305)

We are trying to connect to another server which is running on Jboss 4 and trying to access a remote EJB (session bean). Till now I’ve no clear idea about this whole issue. If any of you can put some light to this issue, please.

I will update this place once we tackle the issue.

Update 1:
I found some useful information here: https://jira.jboss.org/jira/browse/EJBTHREE-749

The problem seems to be mismatching SerialVersionUID in org.jboss.ejb3.remoting.IsLocalInterceptor of  jboss-ejb3-client.jar.

Update 2: 28-Jan-2009
This issue has been fixed from Jboss-4.2.2 GA onwards. So all those who are using versions lesser than 4.2.2 are more likely to get this issue.

Find the JIRA post by Venu here: https://jira.jboss.org/jira/browse/EJBTHREE-1696