Transient / network class loader

i hope to understand exactly what "transient" means in the context of remote class loading.
i am serializing an object on a local machine.
send it over a socket to remote machine.
remote machine de-serializes.
it needs the classes to de-serialize.
calls back to the local machine.
gets the classes.
ok.
issue:
i am looking at the classes that the { java.io.ObjectInputStream "resolveClass(ObjectStreamClass desc);" }
is requesting for loading during the de-serialization process.
and see that the classes for the objects that i marked as "transient" are still being requested.
i did not expect this.
my marking objects as "transient" means those objects are not a part of an object's persistent "state".
yet, the classes for the transient objects are still requested.
do i not understand transient?

i hope to understand exactly what "transient" means in the context of remote class loading.The context is irrelevant. 'transient' has the same meaning in all contexts. It means the field(s) so marked is/are ignored by Java Serialization.
and see that the classes for the objects that i marked as "transient" are still being requested.By the class loader. The class loader doesn't care about 'transient'. The receiver will still need those classes if it uses that field. The class loader can't assume that it won't do that. So it loads the classes of the transient objects. Just like it loads the superclasses, and the classes of all the other fields, member and static.

Similar Messages

Dynamic class loading over a network

hi,
Im tryin to run a simple little "Hello World" type app using RMI. What i want to know is what permissions i need to grant inorder to dynamically load (client side) the stubs and skeletons from my server. Currently i get an UnmarshalException with a nested ClassNotFoundException and the helpful message "access denied to class loader". Any help is appreciated.
Thanks in advance,
Alex

It is hard to tell what the problem is with out a stack trace from the exception. Perhaps in the future you would be kind enough to supply one.

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 failed, why?

Hi there!
We are using WebLogic 5.1 togehter with Apache1.3.22/Tomcat4.01. It all worked
fine for about 2 month. All of a sudden, dynamic class loading refuses to work.
From one day to the other I got the excpetion: javax.naming.CommunicationException.
Root exception is weblogic.rmi.UnmarshalException: Unmarshalling return
- with nested exception:
[java.lang.ClassNotFoundException: class com.dsh.egb.aks.betrieb.ejbs.AnmeldenEJBHomeImpl_ServiceStub
previously not found]
Why does this happen? I can not remember having touched any properties.
Please help,
Heiner

If you were relying on client network classloading stubs from WebLogic, you
can test if it still works by pointing your browser to
htpp://yourweblogic:7001/classes/com/dsh/egb/aks/betrieb/ejbs/AnmeldenEJBHomeImpl_ServiceStub.class
Heiner Amthauer <[email protected]> wrote:
Hi there!
We are using WebLogic 5.1 togehter with Apache1.3.22/Tomcat4.01. It all worked
fine for about 2 month. All of a sudden, dynamic class loading refuses to work.
From one day to the other I got the excpetion: javax.naming.CommunicationException.
Root exception is weblogic.rmi.UnmarshalException: Unmarshalling return
- with nested exception:
[java.lang.ClassNotFoundException: class com.dsh.egb.aks.betrieb.ejbs.AnmeldenEJBHomeImpl_ServiceStub
previously not found]
Why does this happen? I can not remember having touched any properties.
Please help,
Heiner--
Dimitri

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??

RMI Dynamic Class Loading

Hello,
I have a standalone Java Client which is connecting to an RMI based svr component on WLS 6.0sp1. However, before connecting to the RMI Svr, I am trying to boot strap couple of other CLASS files from the App Svr. using the RMIClassLoader. Now here's the problem...
I have placed my classes( one which I want to download and instantiate before I start making conventional calls to RMI Svr remote methods) in the folder WL_HOME/config/examples/rmi/*.class
which is the code_base url I use. However, the error I get when trying to download the classs using RMIClass loader is:
No Security Manager: RMI Class Loader disabled"...
due to which I can not even get connected to my remote object after that. Can somebody please tell me how can I set whatever option it is so that I can get this thing working.
I tried using the "Grant all" security policy too on the client side & server side in vain.
Any help is truly appreciated. Thanks a lot!
cl I am trying to

I'll try having a crack at this, see inline comments
Chirag Shah wrote:
Hello,
I have a standalone Java Client which is connecting to an RMI based svr component on WLS 6.0sp1. However, before connecting to the RMI Svr, I am trying to boot strap couple of other CLASS files from the App Svr. using the RMIClassLoader. Now here's the problem...
I have placed my classes( one which I want to download and instantiate before I start making conventional calls to RMI Svr remote methods) in the folder WL_HOME/config/examples/rmi/*.class
which is the code_base url I use. However, the error I get when trying to download the classs using RMIClass loader is:I'll assume that you're using a proper URL (file://) to instanciate your ClassLoader.
>
No Security Manager: RMI Class Loader disabled"...
Does your client explicitly set a SecurityManager using the following command?
if (System.getSecurityManager() == null) {
System.setSecurityManager(new java.rmi.RMISecurityManager());
Also,I believe that it should only be your client changing its policy file (for the network classload).
>
due to which I can not even get connected to my remote object after that. Can somebody please tell me how can I set whatever option it is so that I can get this thing working.
I tried using the "Grant all" security policy too on the client side & server side in vain.
Any help is truly appreciated. Thanks a lot!
cl I am trying toHope it helps,
Stephane Vaucher
CIRANO
Research Professional

Dynamic Class Loading (RMI)

Hi,
i have my rmi server, implementing objects,stubs and skeleton classes deployed in my Tomcat server and they are stored under the tomcat root folder.
In anoather jvm iam trying to load the classes thru the below code.
java -Djava.rmi.server.codebase=http://ssd8/tomcat-3.2.4/install_dir/webapps/ROOT/WEB-INF/rmicode stockMarketClient
ssd8 is the hostname(machine) which contains all my rmi server files.
and stockmarketclient is my rmi client.
Iam getting the java.lang.noclassdeffound error.
what may be the problem???
Should i have the security policy file in the client machine.

Please Do tell me if any of the following worked I'll be greatly obliged
1) Try this
java -Djava.rmi.server.codebase=http://servername/dir1/dir2/ RMIServer
This / thing at the end of the URL is very important
2) This is how I did it just Today
Dynamic Class Loading Using RMI
     Server Side
1) Main Interface
2) Implementing Class
3) Stub & Skel                    (RMI Server & Web Server)
4) All Other Classes used by the Server
     Web Server Side
1) Main Interface
2) Stub & Skel                    (RMI Server & Web Server)
3) All Other Classes (not Main Client Class)
     Client Side
1) Main Interface
2) Main Client Class
3) Stubs
4) Security Manager
     RUNNING
SERVER
     java DataServerImpl
CLIENT
     java DataClient xyz
Note
Make Calls as follows
System.setSecurityManager(new LaxSecurityManager());
DataServer server = (DataServer) Naming.lookup("rmi://localhost:1099/DataServer");
Runnable r = (Runnable)server.getNewClass();
r.run();
DON'T make Calls as follows
System.setSecurityManager(new LaxSecurityManager());
DataServer server = (DataServer) Naming.lookup("rmi://localhost:1099/DataServer");
NewClass obj = server.getNewClass();
obj.run();
if done as above provide the Class NewClass to the Client as well ( whole purpose defeated)
Code
     // SecurityManager
import java.rmi.*;
import java.security.*;
public class LaxSecurityManager extends RMISecurityManager
     // All Checks are routed through this method
     public void checkPermission(Permission p)
          // do nothing
     // Main Interface
import java.rmi.*;
public interface DataServer extends Remote
     public boolean login(String usr_name,char[] pass_wrd) throws RemoteException;
     public Object getNewClass() throws RemoteException;
     // Main Server
import java.rmi.*;
import java.rmi.server.*;
import java.rmi.registry.*;
public class DataServerImpl /*extends UnicastRemoteObject*/ implements DataServer
     static
          try
               LocateRegistry.createRegistry(1099);
          catch(Exception e)
               System.err.println("Static " + e);
     public boolean login(String usr_name,char[] pass_wd) throws RemoteException
          System.out.println("Welcome " + usr_name);
          if( pass_wd == null || pass_wd.length == 0 || pass_wd.length > 10 )
               return false;
          return true;
     public Object getNewClass() throws RemoteException
          System.out.println("Returning New Class");
          return new NewClass();
     public DataServerImpl() throws RemoteException
          try
               System.setProperty("java.rmi.server.codebase","http://localhost:8080/");
               UnicastRemoteObject.exportObject(this);
               Naming.rebind("DataServer",this);
          catch(java.net.MalformedURLException e)
               System.err.println("DataServerImpl " + e);
               return;
          System.out.println("Server Registered");
     public static void main(String[] args) throws Exception
          new DataServerImpl();
     // Class Moving Around the Network
public class NewClass implements java.io.Serializable,Runnable
     int num;
     public void run()
          System.out.println("Start the Server with Number = " + num);
     public NewClass()
          num = (int)(Math.random()*1000);
     public String toString()
          return num + "";
     // Client
import java.rmi.*;
public class DataClient
     public static void main(String[] args) throws Exception
          System.setSecurityManager(new LaxSecurityManager());
          String pass = new String();
          if(args.length == 0)
               System.err.println("usage: java DataClient PassWord");
               System.exit(1);
          else
               pass = args[0];
          DataServer server = (DataServer) Naming.lookup("rmi://localhost:1099/DataServer");
          Runnable r = (Runnable)server.getNewClass();
          r.run();
All the Best

New to dynamic class loading - could you help me?

Hi all!
Thanks so much for taking a minute to read my post.
I am a rookie at java and programming.
I have a program that needs to load a class (or java file) dynamically during runtime. (At least I think that is what it needs to do.)
I want the user of the program to be able to specify a .java or a .class file either somewhere on the local disk or network, but not necessarily in the same location as the program itself. Once that file is selected, I would like the program to be able to use that file as if it were a .class file created in the working directory when the program was compiled and created.
I have read a lot of the forums, and I think I need to write my own class loader. I tried creating a class loader, and the code is shown below. (I borrowed this code from some of the other forums I've read.)
Here is my problem.
1. Should I be trying to extend the ClassLoader class? Am I on the right track?
2. If I am on the right track, should I require the user of my program to select a previously compiled ".class" file? Or should I ask them to indicate a ".java" file, and try to compile the java file with the program?
3. I'm sure that if the above two questions are answered, the solution to this problem will become obvious. But for clarity, I should mention that with the current code (below), I keep getting a java.lang.NoClassDefFoundError inside the class FileClassLoader at the line:
c = defineClass (classname, buff, 0, buff.length); Obviously, I am not providing the right information to this FileClassLoader in order to create the class. Can you help me out?
Thank you in advance!
I really appreciate it!
Best Regards,
Julia
class SampleClass
public void sampleMethod()
   final JFileChooser fc = new JFileChooser();
   int returnVal = fc.showOpenDialog(optionPane);
   if (returnVal == JFileChooser.APPROVE_OPTION) {
     File file = fc.getSelectedFile();
     try
        FileClassLoader loader = new FileClassLoader(file);
           Class cl = loader.loadClass(file.getName(),false);
        }catch ( ClassNotFoundException e ) {
       System.out.println("ClassNotFoundException");
     }catch (IllegalAccessException e) {
       System.out.println("IllegalAccess");
     }catch( InstantiationException e) {
       System.out.println("Can't Instantiate That");
class FileClassLoader extends ClassLoader
     private File file;
     public FileClassLoader (File thisFile)
          this.file = thisFile;
     protected synchronized Class loadClass(String s, boolean bool) throws ClassNotFoundException
          Class c = null;
          try {
               int size = (int)file.length();
               byte buff[] = new byte[size];
               FileInputStream fis = new FileInputStream(file);
               DataInputStream dis = new DataInputStream (fis);
               dis.readFully (buff);
               dis.close();
               String classname = null;
               String filename = file.getName();
               int i = filename.lastIndexOf('.');
               if(i>0 && i<filename.length()-1)
                    classname = filename.substring(0,i);
               c = defineClass (classname, buff, 0, buff.length);
               resolveClass (c);
          } catch (java.io.IOException e) {
               e.printStackTrace();
          return c;
}

Hi!
If you really need to do that, you can give a look at my previous post at:
http://forum.java.sun.com/thread.jsp?forum=4&thread=285674
You can play with the code to suit your needs.
Hope this helps.

Problem - some networking classes not supported by my MIDP device???

I have a MIDlet I developed which uses java.io.* and javax.microediton.* packages. The MIDlet reads http data and displays it (pretty simple). In fact, it uses some of the sample code from this site.
Runs fine on the emulator, but when loading into the phone (Motorola) the java app loader blows up with this error:
"The selected application cannot be loaded because it contains networking classes or packages that are not allowed.".
Why am I getting this? Shouldn't all MIDP-compliant devices support the packages I'm using?
I checked the jar, there aren't any other files in there that shouldn't be.

It is the JAL - it only supports non-network app downloads. See my other post in this group for downloading network apps.

How to load a class dynamically in the current/system class loader

I need to dynamically load a new jdbc driver jar to the current/system class loader... Please note that creating a new classloader will not help since the DriverManager refers to the systemclassloader itself.
Restarting the application by appending the jar to its classpath will solve the problem but I want to avoid doing this.

Did you then create a ClassLoader to load the JDBC
driver and then install it into the system as
directed by the JDBC specification (ie
Class.forName(someClassName))?
And then try to use it from a class loaded fromsome
other ClassLoader (i.e. the system class loader)?
If you did not try this please explain why not.O.K. I just looked at the source to
java.sql.DriverManager. I did not know what I was
talking about, as what I suggested above will not
work.
This is my new Idea:
Create a URLClassLoader to load the JDBC driver also
in this ClassLoader you need to place a helper class
that does the following:
public class Helper {
public Driver getJDBCDriver(String driverClassName,
String url) {
try {
Class.forName(driverClassName);
Driver d = DriverManager.getDriver(url);
return d;
catch(Exception ex) {
ex.printStackTrace();
return null;
}Now create an instance of the Helper class in the new
ClassLoader, and call its getJDBCDriver method to get
an instance of the driver (you will probably have to
create an interface in the root class loader that the
Helper implements so that you can easily call it).
Now from the root classloader you can make calls
directly to the returned Driver and bypass the
DriverManager and its restrictions on cross
ClassLoader access.
The only catch here is that you would have to call to
the returned Driver directly and not use the Driver
Manager.This sounds like will work but I did not want to load DriverManager in a new classloader.. I did a hack
I unzip the jar dynamically in a previously known location (which I included in my classpath when launching the app). The classLoader finds the class now though it did not exist when the app was launched !
A hack of-course but works eh ..

Error building project using kXML2 - "Class loading error: Wrong name"

Hi,
I'm testing the XML-Parser KXML2 and downloaded the latest package, but the minimal version (kxml2-min.zip). I put this file into the directory "%j2mewtk%\apps\KxmlTest\lib" and wrote the lines
import org.kxml2.io.*;
import org.xmlpull.v1.*;
When I try to build the project with the Wireless Toolkit (v1.04) it spits out the following error:
Error preverifying class kxml2.io.KXmlParser
Class loading error: Wrong name
com.sun.kvem.ktools.ExecutionException: Preverifier returned 1
Build failed
I also tried the full package "kxml2.zip" but the same error occurs.
How can I get rid of this? Thanks in advance!

Okay, finally worked it out (hopefully). I unpacked the archive to a directory (say "%J2MEWTK%\apps\KxmlTest\tmpclasses") and then preverified them "manually":
%J2SDK%\bin\preverify.exe -classpath "%J2MEWTK%\apps\KxmlTest\tmpclasses";"%J2MEWTK%\lib\midpapi.zip" org.kxml2.io.KXmlParser
%J2SDK%\bin\preverify.exe -classpath "%J2MEWTK%\apps\KxmlTest\tmpclasses";"%J2MEWTK%\lib\midpapi.zip" org.xmlpull.v1.XmlPullParser
%J2SDK%\bin\preverify.exe -classpath "%J2MEWTK%\apps\KxmlTest\tmpclasses";"%J2MEWTK%\lib\midpapi.zip" org.xmlpull.v1.XmlPullParserException
Then I packed them again to a jar-file:
%J2SDK%\bin\jar.exe -cvf kxml2-min.jar %J2MEWTK%\apps\KxmlTest\tmpclasses\output\.
That was all!

Performance issues with class loader on Windows server

We are observing some performance issues in our application. We are Using weblogic 11g with Java6 on a windows 2003 server
The thread dumps indicate many threads are waiting in queue for the native file methods:
"[ACTIVE] ExecuteThread: '106' for queue: 'weblogic.kernel.Default (self-tuning)'" RUNNABLE
     java.io.WinNTFileSystem.getBooleanAttributes(Native Method)
     java.io.File.exists(Unknown Source)
     weblogic.utils.classloaders.ClasspathClassFinder.getFileSource(ClasspathClassFinder.java:398)
     weblogic.utils.classloaders.ClasspathClassFinder.getSourcesInternal(ClasspathClassFinder.java:347)
     weblogic.utils.classloaders.ClasspathClassFinder.getSource(ClasspathClassFinder.java:316)
     weblogic.application.io.ManifestFinder.getSource(ManifestFinder.java:75)
     weblogic.utils.classloaders.MultiClassFinder.getSource(MultiClassFinder.java:67)
     weblogic.application.utils.CompositeWebAppFinder.getSource(CompositeWebAppFinder.java:71)
     weblogic.utils.classloaders.MultiClassFinder.getSource(MultiClassFinder.java:67)
     weblogic.utils.classloaders.MultiClassFinder.getSource(MultiClassFinder.java:67)
     weblogic.utils.classloaders.CodeGenClassFinder.getSource(CodeGenClassFinder.java:33)
     weblogic.utils.classloaders.GenericClassLoader.findResource(GenericClassLoader.java:210)
     weblogic.utils.classloaders.GenericClassLoader.getResourceInternal(GenericClassLoader.java:160)
     weblogic.utils.classloaders.GenericClassLoader.getResource(GenericClassLoader.java:182)
     java.lang.ClassLoader.getResourceAsStream(Unknown Source)
     javax.xml.parsers.SecuritySupport$4.run(Unknown Source)
     java.security.AccessController.doPrivileged(Native Method)
     javax.xml.parsers.SecuritySupport.getResourceAsStream(Unknown Source)
     javax.xml.parsers.FactoryFinder.findJarServiceProvider(Unknown Source)
     javax.xml.parsers.FactoryFinder.find(Unknown Source)
     javax.xml.parsers.DocumentBuilderFactory.newInstance(Unknown Source)
     org.ajax4jsf.context.ResponseWriterContentHandler.<init>(ResponseWriterContentHandler.java:48)
     org.ajax4jsf.context.ViewResources$HeadResponseWriter.<init>(ViewResources.java:259)
     org.ajax4jsf.context.ViewResources.processHeadResources(ViewResources.java:445)
     org.ajax4jsf.application.AjaxViewHandler.renderView(AjaxViewHandler.java:193)
     org.apache.myfaces.lifecycle.RenderResponseExecutor.execute(RenderResponseExecutor.java:41)
     org.apache.myfaces.lifecycle.LifecycleImpl.render(LifecycleImpl.java:140)
On googling this seems to be an issue with java file handling on windows servers and I couldn't find a solution yet. Any recommendation or pointer is appreciated

Hi shubhu,
I just analyzed your partial Thread Dump data, the problem is that the ajax4jsf framework ResponseWriterContentHandler triggers internally a new instance of the DocumentBuilderFactory; every time; triggering heavy IO contention because of Class loader / JAR file search operations.
Too many of these IO operations under heavy load will create excessive contention and severe performance degradation; regardless of the OS you are running your JVM on.
Please review the link below and see if this is related to your problem.. This is a known issue in JBOSS JIRA when using RichFaces / ajaxJSF.
https://issues.jboss.org/browse/JBPAPP-6166
Regards,
P-H
http://javaeesupportpatterns.blogspot.com/

How can I make server use single class loader for several applications

I have several web/ejb applications. These applications use some common libraries and should share instances of classes from those libraries.
But applications are being deployed independently thus packaging all them to EAR is not acceptable.
I suppose the problem is that each application uses separate class loader.
How can I make AS use single class loader for a set of applications?
Different applications depend on different libraries so I need a way that will not share library for all applications on the domain but only for some exact applications.
When I placed common jar to *%domain%/lib* - all works. But that jar is shared between all applications on the domain.
When I tried to place common jar to *%domain%/lib/applibs* and specified --libraries* attribute on deploying I got exception
java.lang.ClassCastException: a.FirstDao cannot be cast to a.FirstDaoHere http://download.oracle.com/docs/cd/E19879-01/820-4336/6nfqd2b1t/index.html I read:
If multiple applications or modules refer to the same libraries, classes in those libraries are automatically shared.
This can reduce the memory footprint and allow sharing of static information.Does it mean that classes should be able to be casted ?

You didn't specify which version of the application server you are using, but the config is similar as long as you know what to look for. Basically, you need to change the classloader delegation. Here's how it is done in 8.2
http://download.oracle.com/docs/cd/E19830-01/819-4721/beagb/index.html

How can I get a dynamic list of Classes Loaded

I assume this may need to use some sort of reflection. Does
anyone have code or ideas where I can:
a) I can get a list of all Classes loaded and their
properties. This would probably be all instances of Class
b) A list of all
global instance variables. (This may not even be possible. I
know it can be done in other languages)
I assume this may need to use some sort of reflection.
Thank you

Adobe Newsbot hopes that the following resources helps you.
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its utility will be appreciated:
mx.controls.List (Flex 3):
If the data is incorrect, you can call the preventDefault()
method to stop Flex from passing the new data back to the list
control and from closing the
Link:
http://livedocs.adobe.com/flex/3/langref/mx/controls/List.html
Displaying icons in a Flex List control at Flex Examples:
http://blog.flexexamples.com/2007/08/17/displaying-icons-in-a-flex-list-control/
--> <mx:Application xmlns:mx="
http://www.adobe.com/2006/mxml"
Link:
http://blog.flexexamples.com/2007/08/17/displaying-icons-in-a-flex-list-control/
Populate the list -- Flex 2.01:
You populate a list-based form control with the
<mx:dataProvider> child tag. The <mx:dataProvider> tag
lets you specify list items in several ways.
Link:
http://livedocs.adobe.com/flex/201/html/tutorial_controls_019_4.html
Smooth Scroll for Horizontal List - Flex India Community |
Google:
I have created image gallery with Horizontal List[Flex 2.0].
Just as below ref site. My Problem is i need a smooth scroll for
Horizontal List. where images
Link:
http://groups.google.com/group/flex_india/browse_thread/thread/a12441143b98d32c?hide_quote s=no
Creating a List control -- Flex 2.01:
The following example code adds a handler for a change event
to the List control. Flex broadcasts a mx.ListEvent.CHANGE event
when the value of the control
Link:
http://livedocs.adobe.com/flex/201/html/dpcontrols_062_03.html
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How to write a class loader to solve the class confliction in rt.jar?

Hello guys:
The weblogic.jar has the javax.management.*, it is conflict with rt.jar's
I want to use JMX 1.0 to communicate with weblogic 8.1. The client should be run in the Java 1.5
It throw
java.io.InvalidClassException: javax.management.ObjectName; local class incompatible:
stream classdesc serialVersionUID = -5467795090068647408, local class serialVersionUID = 1081892073854801359
java.io.InvalidClassException: javax.management.ObjectName; local class incompatible:
stream classdesc serialVersionUID = -5467795090068647408, local class serialVersionUID = 1081892073854801359I know the reason is java 1.5 has JMX 1.2 in it.
So how can I program a class loader to load the weblogic.jar classes in? I have tried a lot of code, but failed.
Is there any sample here?
I want to use the JMX 1.0 in weblogic.jar at jdk1.5 run time
Thanks a lot,
Qiang

Hello guys:
The weblogic.jar has the javax.management.*, it is conflict with rt.jar's
I want to use JMX 1.0 to communicate with weblogic 8.1. The client should be run in the Java 1.5
It throw
java.io.InvalidClassException: javax.management.ObjectName; local class incompatible:
stream classdesc serialVersionUID = -5467795090068647408, local class serialVersionUID = 1081892073854801359
java.io.InvalidClassException: javax.management.ObjectName; local class incompatible:
stream classdesc serialVersionUID = -5467795090068647408, local class serialVersionUID = 1081892073854801359I know the reason is java 1.5 has JMX 1.2 in it.
So how can I program a class loader to load the weblogic.jar classes in? I have tried a lot of code, but failed.
Is there any sample here?
I want to use the JMX 1.0 in weblogic.jar at jdk1.5 run time
Thanks a lot,
Qiang

Transient / network class loader

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