Help Please.

I’m currently having problems working with dynamic class loading in so far as I consistently get a ClassNotFoundException on attempting to load a class.

I’ve included below the code sample I’ve been using that I extracted from an article Understanding Class.forName (white Paper) that I downloaded from this site at-.

http://www.theserverside.net/developmentor/thread.tss?thread_id=25023

Using the example below I attempt to load a simple class named TmZome that I’ve placed in both the current directory and in my CLASSPATH but still receive the following exception on running the ClassLoader.

java.lang.ClassNotFoundException: TmZone.class
at java.net.URLClassLoader$1.run(URLClassLoader.java:199)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.java:187)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:274)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at spectraejb.ClassLoaderHelper$1.loadClass(ClassLoaderHelper.java:22)
at spectraejb.ClassLoaderHelper.loadClass(ClassLoaderHelper.java:28)
at spectraejb.ClassLoaderHelper.main(ClassLoaderHelper.java:54)
Exception in thread "main"

I’m assuming this is something quite simple that I’m missing on, but any pointers would be greatly appreciated.

Ultimately I intend to implement the class loader in an application running on Oracle 10gAs should that imposes any further considerations.

Regards

Gary.


interface VMClassLoader {
  public Class loadClass(String cls) throws ClassNotFoundException;
}

public class ClassLoaderHelper {
  private static VMClassLoader vmClassLoader;
  static {
    vmClassLoader = new VMClassLoader() {
      public Class loadClass(String cls) throws ClassNotFoundException {
        Thread t = Thread.currentThread();
        ClassLoader cl = t.getContextClassLoader();
        return cl.loadClass(cls);
      }
    };
  }

  public static Class loadClass(String cls) throws ClassNotFoundException {
    return vmClassLoader.loadClass(cls);
  }

  public static java.lang.reflect.Method getMethod(Class clazz, String name) throws
        Exception {
      java.lang.reflect.Method[] methods = clazz.getMethods();
      for (int i = 0; i < methods.length; i++) {
        if (methods[i].getName().equals(name)) {
          return methods[i];
        }
      }
      return null;
    }


  public static void main(String[] args) throws Exception {

  Class clazz =
        ClassLoaderHelper.loadClass(args[0]);

      // java.lang.reflect.Method method =
     // getMethod(clazz, "main");


  // method.invoke(null, new Object[] {newArgs});

  }

Hi Gary,
Please note that Oracle Application Server does not use CLASSPATH environment variable. You have to put your in j2ee/home/lib directory to be picked up by the Server or package in the application.

Please look at the Classloading Whitepaper at http://otn.oracle.com/tech/java/oc4j/pdf/ClassLoadingInOC4J_WP.pdf

Hope that helps !

regards
Debu Panda

http://radio.weblogs.com/0135826/

Thanks Debu,

This appears to be a very useful document

Regards

Gary.