Class Loading order/exception in JRockit 31

Hi all,
We recently migrated to Weblogic 10.3.6 and JRockit 31 1.6 (64 bit). I tried to analyze JVM performance using flight recording. I noticed several (around 200K withing 5 minutes!) ClassNotFoundExceptions in the flight recording, but no big issue in the application. This got me curious and I decided to run with Java run-time options verbose:class=trace. This gave more details in the log. I found that for loading every Weblogic class the JRockit first tried 4-5 times and then successfully loaded the class from the Jar file. So for each class I got this exception trace below. I am attaching the example for how the JVM loaded the weblogic.management.scripting.WLST class. My question is:
1. Is this the expected behavior?
2. Is there a better way to load classes in JRockit?
3. Am I just seeing these exceptions because I am setting the Flight recording at a very verbose level?
Please advise. Thanks in advance.
- Shankar.
+[class ][Fri Sep 21 23:15:37 2012][00514] initiate 621 weblogic/management/scripting/WLST+
+[class ][Fri Sep 21 23:15:37 2012][00514] 621 weblogic/management/scripting/WLST fail (0.00 ms)+
+[excepti][Fri Sep 21 23:15:37 2012][00514][00004] java/lang/ClassNotFoundException: weblogic.management.scripting.WLST+
at jrockit/vm/Classes.forName(Classes.java:130)
at java/lang/ClassLoader.findBootstrapClass(Ljava/lang/String;)Ljava/lang/Class;(Native Method)
at java/lang/ClassLoader.findBootstrapClassOrNull(ClassLoader.java:926)
at java/lang/ClassLoader.loadClass(ClassLoader.java:297)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at sun/misc/Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at java/lang/ClassLoader.loadClass(ClassLoader.java:247)
at weblogic/WLST.main(WLST.java:27)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
--- End of stack trace
+[excepti][Fri Sep 21 23:15:37 2012][00514][00004] java/lang/ClassNotFoundException: weblogic.management.scripting.WLST+
at java/net/URLClassLoader$1.run(URLClassLoader.java:202)
at jrockit/vm/AccessController.doPrivileged(AccessController.java:254)
at java/net/URLClassLoader.findClass(URLClassLoader.java:190)
at sun/misc/Launcher$ExtClassLoader.findClass(Launcher.java:234)
at java/lang/ClassLoader.loadClass(ClassLoader.java:306)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at sun/misc/Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at java/lang/ClassLoader.loadClass(ClassLoader.java:247)
at weblogic/WLST.main(WLST.java:27)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
--- End of stack trace
+[excepti][Fri Sep 21 23:15:37 2012][00514][00004] java/security/PrivilegedActionException:+
at jrockit/vm/AccessController.doPrivileged(AccessController.java:258)
at java/net/URLClassLoader.findClass(URLClassLoader.java:190)
at sun/misc/Launcher$ExtClassLoader.findClass(Launcher.java:234)
at java/lang/ClassLoader.loadClass(ClassLoader.java:306)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at sun/misc/Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at java/lang/ClassLoader.loadClass(ClassLoader.java:247)
at weblogic/WLST.main(WLST.java:27)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
--- End of stack trace
+[excepti][Fri Sep 21 23:15:37 2012][00514][00004] java/security/PrivilegedActionException:+
at jrockit/vm/AccessController.doPrivileged(AccessController.java:258)
at java/net/URLClassLoader.findClass(URLClassLoader.java:190)
at sun/misc/Launcher$ExtClassLoader.findClass(Launcher.java:234)
at java/lang/ClassLoader.loadClass(ClassLoader.java:306)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at sun/misc/Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at java/lang/ClassLoader.loadClass(ClassLoader.java:247)
at weblogic/WLST.main(WLST.java:27)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
--- End of stack trace
+[excepti][Fri Sep 21 23:15:37 2012][00514][00004] java/lang/ClassNotFoundException: weblogic.management.scripting.WLST+
at java/net/URLClassLoader$1.run(URLClassLoader.java:202)
at jrockit/vm/AccessController.doPrivileged(AccessController.java:254)
at java/net/URLClassLoader.findClass(URLClassLoader.java:190)
at sun/misc/Launcher$ExtClassLoader.findClass(Launcher.java:234)
at java/lang/ClassLoader.loadClass(ClassLoader.java:306)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at sun/misc/Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at java/lang/ClassLoader.loadClass(ClassLoader.java:247)
at weblogic/WLST.main(WLST.java:27)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
--- End of stack trace
+[excepti][Fri Sep 21 23:15:37 2012][00514][00004] java/lang/ClassNotFoundException: weblogic.management.scripting.WLST+
at java/net/URLClassLoader$1.run(URLClassLoader.java:202)
at jrockit/vm/AccessController.doPrivileged(AccessController.java:254)
at java/net/URLClassLoader.findClass(URLClassLoader.java:190)
at sun/misc/Launcher$ExtClassLoader.findClass(Launcher.java:234)
at java/lang/ClassLoader.loadClass(ClassLoader.java:306)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at sun/misc/Launcher$AppClassLoader.loadClass(Launcher.java:308)
at java/lang/ClassLoader.loadClass(ClassLoader.java:295)
at java/lang/ClassLoader.loadClass(ClassLoader.java:247)
at weblogic/WLST.main(WLST.java:27)
at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method)
--- End of stack trace
+[load ][Fri Sep 21 23:15:37 2012][00514] define #556 weblogic/management/scripting/WLST, src=file:/opt/apps/weblogic11g/wlserver_10.3/server/lib/weblogic.jar+

Hi Shankar,
I seen several BUGs based on this issue better open a ticket with WLS support.
Regards,
Kal

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Hello everyone
I have run in to very strange behavior of JVM
I have created a class loader which allows my to load classes from
jar file, regardless that URLClassLoader supplies this functionality.
I am using this class loader to load some classes and call their virtual functions. The class diagram looks like that:
public interface I {
   public void init();
public class AAA implements
   public void init(){
public class BBB extends AAA{
   public void init(){
      //here comes implementation
}Interface I and class AAA are loaded with System Class loader and Class BBB is loaded using my class loader from jar file.
ByteStreamClassLoader classLoader = new ByteStreamClassLoader ();
Class cl = classLoader. loadClass(�com.product.BBB�,true);
I myInterface = cl.newInstance();
myInterface.init();The problem is that from some unknown reason java class AAA.init() instead of BBB.init().
Can somebody help me what am I doing wrong?
Class Loader code attached below
public class ByteStreamClassLoader   extends ClassLoader {
    protected HashMap m_cache = new HashMap();
    public void clearCashe() {
      m_cache = new HashMap();
    private String definePackage(String className) {
      StringBuilder strB = new StringBuilder();
      //Class name must be removed from the URI in order to define a package
      String[] packageArray = className.split("\\.");
      for (int i = 0; i < packageArray.length - 1; i++) {
        strB.append(packageArray).append(".");
String packageName = strB.toString();
packageName = packageName.substring(0, packageName.length() - 1);
if (getPackage(packageName) == null) {
m_logger.log(Level.FINEST, "Defining package '" + packageName + "'");
definePackage(packageName, null, null, null, null, null, null, null);
return packageName;
public synchronized Class loadClass(String name, boolean resolve) throws
ClassNotFoundException {
name = name.replaceAll("/", ".").replaceAll(".class", "");
//Try to locate the Class in cashe
Class c = (Class) m_cache.get(name);
//Try to locate the Class in the System Class Loader
if (c == null) {
try {
c = ClassLoader.getSystemClassLoader().loadClass(name);
catch (Exception ex) {}
else {
m_logger.log(Level.FINEST, "Class '" + name + "' found in cache");
//Load the class from byte array
if (c == null) {
String resourceName = name;
if (!resourceName.endsWith(".class")) {
resourceName = resourceName.concat(".class");
//Retrieve class byte representation
if (resourceName.indexOf(".") != -1) {
resourceName =
resourceName.replaceAll("\\.", "/").replaceAll("/class", ".class");
//Use the ByteStreamClassLoader to load the class from byte array
byte[] classByteArray = null;
try {
classByteArray = getResourceBytes(resourceName);
catch (IOException ex1) {
throw new ClassNotFoundException(
"Could not load class data." + ex1.getMessage());
m_logger.log(
Level.FINEST, "Loading class '" +
name + "' Byte Length: " + classByteArray.length);
String p = definePackage(name);
c = defineClass(
name,
classByteArray,
0,
classByteArray.length,
ByteStreamClassLoader.class.getProtectionDomain());
m_cache.put(name, c);
if (resolve) {
resolveClass(c);
return c;

Hibernate in Weblogic10 : class not found exception

Hi All,
I am using JPA/Hibernate in Weblogic 10. While running the application, I am getting the following exception. Can someone help on this.
Exception caught is : java.lang.IllegalArgumentException : org.hibernate.QueryException : ClassNotFoundException : org.hibernate.hql.ast.HqlToken [select p from ParentProfileEntity p where p.email=?1]
I am using JBoss's seam framework . Copy of the persistence.xml is given below.
     <persistence-unit name="userDatabase" transaction-type="JTA">
     <provider>org.hibernate.ejb.HibernatePersistence</provider>
     <jta-data-source>PNDataSource</jta-data-source>
     <properties>
     <property name="hibernate.archive.autodetection" value="class, hbm"/>
          <property name="hibernate.show_sql" value="true"/>
          <property name="hibernate.format_sql" value="true"/>
          <property name="use_sql_comments" value="true"/>
          <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
          <property name="hibernate.transaction.manager_lookup_class" value="org.hibernate.transaction.WeblogicTransactionManagerLookup"/>
     </properties>
     </persistence-unit>
     </persistence>

Hi,
It's a problem with the antlr lib that also exist in weblogic.
You can configure the class loader search order:
Add a file META-INF/weblogic-application.xml in your EAR:
<?xml version="1.0" encoding="ISO-8859-1"?>

<weblogic-application>
     <prefer-application-packages>
           <package-name>antlr.*</package-name>
     </prefer-application-packages>
</weblogic-application>You must provide the antlr lib within the EAR.
Should be ok after that....
Olivier

Dynamic Class Loading in an EJB Container

Hello,
We have a need to load classes from a nonstandard place with in an ejb container, ie a database or secure store. In order to do so we have created a custom class loader. Two issues have come up we have not been able to solve, and perhaps some one knows the answer to.
Issue 1.
Given the following code:
public static void main(String args[])
MyClassLoader loader = new MyClassLoader("lic.dat");
System.out.println("Loading class ..." + "TestObject");
Object o = Class.forName("TestObject",true,loader).newInstance();
System.out.println("Object:" + o.toString());
TestObject tstObj = (TestObject) o;
tstObj.doIt();
What happens when executed is as follows. Class.forName calls our loader and does load the class as we hoped, it returns it as well, and the o.toString() properly executes just fine. The cast of the object to the actual TestObject fails with a class not found exception. We know why this happens but don't know what to do about it. It happens because the class that contains main was loaded by the system class loader (the primordial class loader as its sometimes called), That class loader does not know about TestObject, so when we cast even though the class is "loaded" in memory the class we are in has no knowledge of it, and uses its class loader to attempt to find it, which fails.
> So the question is how do you let the main class know to use our class loader instead of
the system class loader dispite the fact is was loaded by the system class loader.
Issue 2:
To make matters worse we want to do this with in an EJB container. So it now begs the question how do you inform an EJB container to use a specific class loader for some classes?
Mike...

Holy crap! We are in a similar situation. In creating a plugin engine that dynamically loads classes we use a new class loader for each plugin. The purpose is so that we can easily unload and/or reload a class at runtime. This is a feature supposedly done by J2EE app servers for hot-deploy.
So our plugins are packaged as JAR files. If you put any class in the CLASSPATH, the JVM class loader (or the class loader of the class that is loading the plugin(s)), will load the class. The JavaDoc API states that the parent classloader is first used to see if it can find the class. Even if you create a new URLClassLoader with NULL for parent, it will always use the JVM class loader as its parent. So, ideally, in our couse, plugins will be at web sites, network drives, or outside of the classpath of the application and JVM.
This feature has two benefits. First, at runtime, new updates of plugins can be loaded without having to restart the app. We are even handling versions and dependencies. Second, during development, especially of large apps that have a long startup time, being able to reload only one plugin as opposed to the annoying startup time of Java apps is great! Speeds up development greatly.
So, our problem sounds just like yours. Apparently, the Client, which creates an instance of the plugin engine, tries to access a plugin (after the engine loades it via a new classloader instance for each plugin). Apparently, it says NoDefClassFound, because as you say, the client classloader has no idea about the plugin class loaded by another classloader.
My co-developer came up with one solution, which I really dont like, but seems to be the only way. The client MUST have the class (java .class file) in its classpath in order to work with the class loaded by another class loader. Much like how in an EJB container, the web server calling to EJB MUST contain the Home and Remote interface .class files in its classpath, the same thing needs to be done here. For us, this means if a plugin depends on 5 others, it must contain ALL of the .class files of those plugins it depends on, so that the classloader instance that loads the plugin, can also see those classes and work with them.
Have you got any other ideas? I really dislike that this has to be done in this manner. It seems to me that the JVM should be able to allow various class loaders to work with one another in such a way that if a client loaded by one classloader has an import statement in it to use a class, the JVM should be able to fetch the .class out of the other classloader and share it, or something!
This seems to me that there really is no way to actually properly unload and then reload a class so that the JVM will discard and free up the previous class completely, while using the new class.
I would be interested in discussing this topic further. Maybe some others will join in and help out on this topic. I am surprised there isn't a top-level forum topic about things like class loaders, JVM, etc. I wish there was a way to add one!

Dynamic class loading when CODEBASE is unreachable. A bug?

Let us suppose that we have a large-scale distributed application with ca. 1000 participants communicating via RMI and utilizing dynamic class loading. As we all know, a HTTP code server must be available for this purpose in order to provide dynamically downloaded code, usually the communication proxy code of remote objects. In a real-world scenario, the HTTP server will never be 100% available, so that we will have cases that a Java process will not be able to download the necessary Java classes, causing the RMI communication to fail with a ClassNotFoundException or similar exception. In such a case, a robust application would perform some recovery activities and retry the remote call. Eventually, the HTTP server becomes available again and the distributed system recovers automatically. This seems to work fine with J2SE 1.4.2_10, but not with 1.4.2_11 and newer versions. Considering Java 5, the Update 9 exhibits the same problem.
For tracking down the problem, I've written a simple distributed test application, consisting of a client and a server. A server listens on a port, and sends a MarshalledObject to the client. The code of the MarshalledObject is annotated with the value of the "java.rmi.server.codebase" system property. The annotation contains an URL of the JAR file containing the code of the original object. The client connects to the server, reads data form the socket and unmarshalls the original object. This is basically the same procedure as when objects are accross the wire as arguments/return values/exceptions by the RMI/JRMP engine. This procedure is repeated forever in the loop. Due to the fact that the client's CLASSPATH doesn't contain the code of the original object, this code should dynamically be loaded from the HTTP server using the appropriate annotation provided by the server.
If we start the client while the HTTP server is down, the client will keep generating the ClassNotFoundException over and over again, as expected. So far, so good. If we now start the HTTP server while the client is still running, we will observe different behaviors, depending on the version of the client's JVM:
1. In J2SE 1.4.2_10, the client will download the code from the HTTP server and successfully unmarshal the original object sent by the server. ClassNotFoundExceptions will not be generated again.
2. In J2SE 1.4.2_11, 1.4.2_12 and 1.4.2_13 as well as in J2SE 5.0 Update 9, the client will continue generating ClassNotFoundExceptions. Analysis of the HTTP server's access log shows that there were no attempts to download the JAR file required for unmarshaling the object sent by the server.
It seems that in the newer JVM versions the RMI engine remembers URLs which have failed and does not attempt to access them anymore. Althogh this may have some advantages considering the overall network load, the dynamical class loading becomes practically useless in productive large distributed systems. The very first attempt to load the codebase of the communication peer must succeed, otherwise the whole process must be restarted for the communication to work, which is a very expensive (and for most customers unacceptable) operation in terms of preformance and resources usage.
Should this be seen as a bug or a feature of the JVM? What do you think?
Regards,
Miran
Here is the code to reproduce:
Server code
package server;
import java.net.*;
import java.rmi.*;
import java.io.*;
public class Server implements Serializable {
private int value = 42;
public Server() {
public String toString() {
    return "The Answer is " + value;
public static void main( String[] args ) {
    if( args.length!=1 ) {
      System.out.println( "Usage: server.Server <port>" );
      System.exit( 1 );
    try {
      MarshalledObject data = new MarshalledObject( new Server() );
      int port = Integer.parseInt( args[0] );
      ServerSocket serverSocket = new ServerSocket( port );
      System.out.println( "Accepting connections..." );
      while( true ) {
        Socket s = serverSocket.accept();
        new Thread( new SocketHandler( s, data ) ).start();
    } catch( Exception ex ) {
      ex.printStackTrace();
    System.exit( 0 );
public static class SocketHandler implements Runnable {
    private Socket s;
    private Serializable data;
    public SocketHandler( Socket s, Serializable data ) {
      this.s = s;
      this.data = data;
    public void run() {
      try {
        OutputStream os = s.getOutputStream();
        ObjectOutputStream oos = new ObjectOutputStream( os );
        oos.writeObject( data );
        oos.close();
        os.close();
        s.close();
        System.out.println( "Serving socket succeeded" );
      } catch( Exception ex ) {
        System.out.println( "Serving socket failed" );
        ex.printStackTrace();
Client code
package client;
import java.rmi.*;
import java.net.*;
import java.io.*;
public class Client {
public static void main( String[] args ) {
    if( args.length!=1 ) {
      System.out.println( "Usage: client.Client <port>" );
      System.exit( 1 );
    try {
      if( System.getSecurityManager()==null ) {
        System.setSecurityManager( new RMISecurityManager() );
      int port = Integer.parseInt( args[0] );
      for( int i = 1; true; ++i ) {
        try {
          Socket s = new Socket( "localhost", port );
          InputStream is = s.getInputStream();
          ObjectInputStream ois = new ObjectInputStream( is );
          Object o = ois.readObject();
          ois.close();
          is.close();
          s.close();
          Object umo = ((MarshalledObject) o).get();
          System.out.println( i + ". Retreiving MarshalledObject succeeded: "
                              + umo );
        } catch( Exception ex ) {
          System.out.println( i + ". Retreiving MarshalledObject failed" );
          ex.printStackTrace();
        System.out.println( i + ". Waiting for 10 sec" );
        Thread.sleep( 10000 );
    } catch( Exception ex ) {
      ex.printStackTrace();
    System.exit( 0 );
Start command for the server
java -cp server.jar -Djava.rmi.server.codebase="http://localhost/playground/server.jar" server.Server 33933
Start command for the client
java -cp client.jar -Djava.security.policy=all.policy client.Client 33933
The policy.all file should look as follows
// All permissions
grant {
   permission java.security.AllPermission;
};The server.jar file should only contain the classes from the server package. This file should also be made accessible via HTTP (e.g. by using the Apache HTTP server).
The client.jar file should only contain the classes from the client package.

no body know about this??

Class Loading order/exception in JRockit 31

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