ClassLoader.findLoadedClass (was: ServiceFactory)

[Sascha Brawer <brawer@dandelis.ch>]

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David Holmes <dholmes@dltech.com.au> wrote on Mon, 22 Mar 2004 09:22:43 +1000:

From what I've read, the specification of findLoadedClass and definition of
>the class cache in terms of an initiating classloader, are intended to
>prevent a malicious classloader from breaking the lookup process. If each
>classloader delegates correctly to its parent then there is, as you say, no
>harm. However, if the parent does not play nicely then different class
>instances could be returned.
>
>This seems like a bug in the JDK implementation of findLoadedClass.

Please find attached a testcase for Mauve (put the two files into gnu/
testlet/java/lang/ClassLoader).

My understanding of the API spec [1] is that on line 51 of the testlet,
the result of calling findLoadedClass should be 'klass' because 'loader'
is an initiating loader for "gnu.testlet.java.lang.ClassLoader.TestClass". 

[1] http://java.sun.com/j2se/1.5.0/docs/api/java/lang/
ClassLoader.html#findLoadedClass(java.lang.String)

On JDK 1.4.1_01, the testlet fails because the result returns null. Same
for JamVM, which is based on Classpath.

If people agree that both the JDK and the Classpath-based VMs are buggy,
I'd commit the test case into Mauve and file bug reports with Classpath
and Sun.

-- Sascha

Sascha Brawer, brawer@dandelis.ch, http://www.dandelis.ch/people/brawer/ 

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// Tags: not-a-test

// Copyright (C) 2004 Sascha Brawer <brawer@dandelis.ch>

// This file is part of Mauve.

// Mauve is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.

// Mauve is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Mauve; see the file COPYING.  If not, write to
// the Free Software Foundation, 59 Temple Place - Suite 330,
// Boston, MA 02111-1307, USA.

package gnu.testlet.java.lang.ClassLoader;

/**
 * Used by gnu.testlet.java.lang.ClassLoader.findLoadedClass.
 */
public class TestClass
{
}

[-- Attachment #2.2: findLoadedClass.java --]
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// Tags: JDK1.2
// Uses: TestClass

// Copyright (C) 2004 Sascha Brawer <brawer@dandelis.ch>

// This file is part of Mauve.

// Mauve is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.

// Mauve is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License
// along with Mauve; see the file COPYING.  If not, write to
// the Free Software Foundation, 59 Temple Place - Suite 330,
// Boston, MA 02111-1307, USA.

package gnu.testlet.java.lang.ClassLoader;

import gnu.testlet.Testlet;
import gnu.testlet.TestHarness;


/**
 * @author <a href="mailto:brawer@dandelis.ch">Sascha Brawer</a>
 */
public class findLoadedClass
  implements Testlet
{
  public void test(TestHarness h)
  {
    CustomClassLoader loader;
    String name;
    Class klass;

    // Check #1: Ask a ClassLoader to load a class, then check
    // whether its findLoadedClass method returns it.
    //
    // Fails with JDK 1.4.1_01 (for GNU/Linux on IA-32) because
    // its ClassLoader.findLoadedClass returns null here.
    loader = new CustomClassLoader();
    name = "gnu.testlet.java.lang.ClassLoader.TestClass";
    try
      {
        klass = loader.loadClass(name);
        h.check(loader.callFindLoadedClass(name), klass);
      }
    catch (ClassNotFoundException cnfex)
      {
        h.check(false);
        h.debug(cnfex);
      }
  }

  
  private static class CustomClassLoader
    extends ClassLoader
  {
    /**
     * Returns the result of calling the protected method {@link
     * ClassLoader#findLoadedClass}.
     */
    public Class callFindLoadedClass(String name)
    {
      return findLoadedClass(name);
    }
  }
}