Jonathan Lalou's Blog

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By default, mvn archetype:generate offers ~50 template projects. How to offer more templates?

Actually, Maven bases itself on a archetype-catalog.xml file, in Maven’s local repository. Updating this file is possible, by mvn archetype:crawl (and/or archetype:update-local-catalog ?).
Anyway, Maven can base on a remote repository, using archetypeCatalog, such as:
[java]mvn archetype:generate -DarchetypeCatalog=http://download.java.net/maven/2[/java]

You can hint at the remote repository available in settings.xml file, for instance.

Case

On generating Locals and Remotes of EJBs (let’s say JonathanBean) to be deployed on JOnAS, the GenIC raises:
[java]GenIC.fatalError : GenIC fatal error: Cannot read the Deployment Descriptors from /foo/goo/jonathan-server.jar: Method foo of interface lalou.jonathan.JonathanLocal should NOT throw RemoteException[/java]

Within the EJB2, the method foo is declared to be Local and to throw RemoteException

Quickfix

The error is explicit.

A Local EJB cannot throw RemoteException.
Especially, the considered method can be declared with the right XDocLet tag, ie:

[java]* @ejb.interface-method view-type="remote"[/java]

but can with neither:
[java]* @ejb.interface-method view-type="both"[/java]

nor:
[java]* @ejb.interface-method view-type="local"[/java]

As a quickfix, I suggest to surround with a try/catch block a throw a RuntimeException if needed.

Case:

You have many files with the same names (log4.xml, applicationContext.xml, etc.), you need know which of them is loaded.

Tip:

On the debugger and/or in the logs, use an instruction similar to:

getClass().getClassLoader().getResource("log4j.xml")

On server side:

an EJB2 packaged in a JAR within an EAR, deployed on JOnAS 5.

On client side:

java.lang.ClassNotFoundException: org.ow2.jonas_gen.com.clam.indice.api.interfaces.JOnASHelloWorldService150707405Home_Stub (no security manager: RMI class loader disabled)]

Explanation:

This means there is some kind of issue with generated Stubs on client side. Should check whether the Stubs depended on are available in classpath.

Case

Trying to deploy an EAR on JOnAS, I got the following error:
[java]Problems when invoking main method from GenIC: java.lang.RuntimeException: error in fastrmic (null)[/java]

More detail:

[java]JOnASEJBService.__checkGenIC : Cannot apply GenIC on the file ‘C:\jonathan\jonathan_2012.05.11-13.47.29.ear\jonathan-server.jar’ with the args ‘[-classpath, C:\jonathan\jonathan_2012.05.11-13.47.29.ear\jonathan-server.jar, -protocols, jrmp, -invokecmd]’.
org.ow2.jonas.service.ServiceException : Problems when invoking main method from GenIC: java.lang.RuntimeException: error in fastrmic (null)
at org.ow2.jonas.generators.genic.wrapper.GenicServiceWrapper.callGenic(GenicServiceWrapper.java:79)
at org.ow2.jonas.ejb2.internal.JOnASEJBService.__callGenic(JOnASEJBService.java:2017)[/java]

Quickfix

Edit $JONAS_BASE/conf/jonas.properties.
The properties jonas.services and jonas.service.ejb2.auto-genic must be consistent.

Especially, if GenIC is enabled (jonas.service.ejb2.auto-genic true), then check ejb2 is among the services pointed at by jonas.services, eg:
jonas.services jtm,db,security,resource,ejb2,web,ear.

Case

The project on which I work is built on Eclipse and Ant. I am trying to migrate it to Maven 3.0. I thought to do this within IntelliJ IDEA.
Once the pom.xml was created, I wanted to revert to a configuration based on Eclipse’s .classpath file.
Then IntelliJ IDEA crashes. On starting up again, I get the following error

[java]Cannot load module file ‘jonathanModule’ Unsupported classpath format eclipse[/java]

Quick Fix

For a reason I ignore, Eclipse integration plugin was disabled. To restore Eclipse compatibility, simply do enable Eclipse integration in the plugin preference menu of IntelliJ IDEA.

JOnAS 4 (and older) and JProfiler 4 (and older) were used to working smoothly. JOnAS 5 makes a large use of OSGi libraries… which may “blind” JProfiler.

Here is a workaround, slightly different from former version, to bypass this issue, in order to make JProfiler 5 work with JOnAS 5:

• let’s assume you have installed JOnAS in a folder, let’s say JONAS_ROOT
• install JProfiler 5 with default options, set the JDK, licence key, etc., let’s say in a folder C:\win32app\jprofiler5\ also known as JPROFILER_HOME.
• edit %JONAS_ROOT%/bin/setEnv.bat:
  • set: JAVA_OPTS=-agentlib:jprofilerti=port=8849 "-Xbootclasspath/a:C:\win32app\jprofiler5\bin\agent.jar" %JAVA_OPTS%
• edit %JONAS_ROOT%/conf/osgi/default.properties
  • in the property bootdelegation-packages, add the JProfiler packages:

[java]
bootdelegation-packages com.sun.corba, \
com.sun.corba.*, \
(…)
com.jprofiler, \
com.jprofiler.*, \
com.jprofiler.agent, \
com.jprofiler.agent.*[/java]

• add JPROFILER_HOME\bin\windows to your environment variable PATH.
• startup JOnAS, you should see the following block in standard output:

[java]JProfiler> Protocol version 25
JProfiler> Using JVMTI
JProfiler> 32-bit library
JProfiler> Listening on port: 8849.
JProfiler> Native library initialized
JProfiler> Waiting for a connection from the JProfiler GUI …
JProfiler> Using dynamic instrumentation
JProfiler> Time measurement: elapsed time
JProfiler> CPU profiling enabled
JProfiler> Hotspot compiler enabled
JProfiler> Starting org/ow2/jonas/commands/admin/ClientAdmin …[/java]

• run JProfiler, follow the wizard, take caution to set JProfiler port at 8849 (or remain consistent with the port set in JOnAS config file)

This week I have started a new position as transverse architect at Amundi Asset Management in Paris (France).
I have to manage the project of Stabilization and Reliability of the platform (tens of JOnAS servers, EJB2 to migrate to EJB3, JVM tuning, etc.). I will have to face hard technical challenges.

I wish I’ll spend a nice time with my new team!

Today in interview I have also been asked the following question: in Java, what is the difference between the methods wait() and sleep()?

First of all, wait() is a method of Object, meanwhile sleep() is a static method of Thread.

More important: Thread.sleep() freezes the execution of the complete thread for a given time. wait(), on its side, gives a maximum time on which the application is suspended: the waiting period may be interrupted by a call to the method notify() on the same object.

Today, in recruting interview, I have been asked the following question: what is the difference between the Java reserved word synchronized used on a method and this very word in a block? Happily I have known the answer:

Indeed, synchronized uses an Object to lock on. When a methid is synchronized, this means the current object is the locker.
Eg: this piece of code:
[java] public synchronized void foo(){
System.out.println("hello world!!!");
}
[/java]
is equivalent to that:
[java] public void foo(){
synchronized (this) {
System.out.println("hello world!!!");
}
}
[/java]
Besides, when synchronized is used on a static method, the class itself is the locker.
Eg: this piece of code:
[java] public static synchronized void goo() {
System.out.println("Chuck Norris");
}
[/java]is equivalent to that:
[java] public static void goo() {
synchronized (MyClass.class) {
System.out.println("Chuck Norris");
}
}
[/java]