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From "Alberto Romei" <a.ro...@centrosistemi.it>
Subject Custom ClassLoader
Date Fri, 11 Apr 2003 11:23:15 GMT
Hi, all !

I need to tell tomcat to use a custom implementation of ClassLoader for a
specific context.

The documentation explains the use of  <Loader loaderClass="pkg.ClassName">
inside the <Context> element, but I saw that the "loaderClass" attribute is
ignored (bug #12501).
The only way I found is to create a subclass of WebappLoader and specify it
in <Loader className="prova.MyLoader">, tweaking the getClassLoader()
method.
Here is the code of my experiment :

= = = = = = = = = =
package prova;

import java.io.*;
import java.net.*;
import org.apache.catalina.loader.WebappLoader;
import org.apache.catalina.loader.WebappClassLoader;

public class MyLoader extends WebappLoader
{
  static
  {
    System.out.println("*****************Here I am*******************");
  }

  ClassLoader cl;
  public MyLoader()
  {
    super();
  }

  public MyLoader(java.lang.ClassLoader parent)
  {
    super(parent);
  }


  public ClassLoader getClassLoader()
  {
    if (cl==null)
    {
      URLClassLoader push = (URLClassLoader)super.getClassLoader();
      cl = new URLClassLoader(push.getURLs(), push)
      {
         public String toString()
         {
           String rv = "***** Prova *****\r\n";
           URL arr[] = ((WebappClassLoader)this.getParent()).getURLs();
           for (int i=0; i<arr.length; i++)
             rv += arr[i]+"\r\n";
           rv += "***** Prova *****\r\n";
           rv += super.toString();
           return rv;
         }
      };
    }
    return cl;
  }
}
= = = = = = = = = =


I placed the class under tomcat/common/classes and it is loaded normally (i
see "*****************Here I am*******************" in the output), but
tomcat cannot compile JSPs any more. When I make a request to a jsp, I get
errors like:
  Class javax.servlet.http.HttpServlet not found...
  Package javax.servlet not found in import...

It seems like the classloader has lost all the paths, even if I set the
parent of my ClassLoader to the default WebappClassLoader.

Any suggestion is appreciated...

Thanks
Alberto








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