BshClassLoader.java

/**
 *
 * This file is a part of ZOOLA - an extensible BeanShell implementation.
 * Zoola is based on original BeanShell code created by Pat Niemeyer.
 *
 * Original BeanShell code is Copyright (C) 2000 Pat Niemeyer <pat@pat.net>.
 *
 * New portions are Copyright 2012 Rafal Lewczuk <rafal.lewczuk@jitlogic.com>
 *
 * This is free software. You can redistribute it and/or modify it under the
 * terms of the GNU Lesser General Public License as published by the Free Software
 * Foundation, either version 3 of the License, or (at your option) any later
 * version.
 *
 * This software 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 Lesser General Public License for more
 * details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with ZOOLA. If not, see <http://www.gnu.org/licenses/>.
 *
 */

package bsh.classpath;

import java.net.*;
import java.util.*;
import java.io.*;
import bsh.BshClassManager;

/**
	One of the things BshClassLoader does is to address a deficiency in
	URLClassLoader that prevents us from specifying individual classes
	via URLs.
*/
public class BshClassLoader extends URLClassLoader 
{
	BshClassManager classManager;

	/**
		@param bases URLs JARClassLoader seems to require absolute paths 
	*/
	public BshClassLoader( BshClassManager classManager, URL [] bases ) {
		super( bases );
		this.classManager = classManager;
	}

	/**
		@param bases URLs JARClassLoader seems to require absolute paths 
	*/
	public BshClassLoader( BshClassManager classManager, BshClassPath bcp ) {
		this( classManager, bcp.getPathComponents() );
	}

	/**
		For use by children
		@param bases URLs JARClassLoader seems to require absolute paths 
	*/
	protected BshClassLoader( BshClassManager classManager ) { 
		this( classManager, new URL [] { } );
	}

	// public version of addURL
	public void addURL( URL url ) {
		super.addURL( url );
	}

	/**
		This modification allows us to reload classes which are in the 
		Java VM user classpath.  We search first rather than delegate to
		the parent classloader (or bootstrap path) first.

		An exception is for BeanShell core classes which are always loaded from
		the same classloader as the interpreter.
	*/
	// todo pejobo70 this could be one of the root causes for issue#34
	public Class loadClass(String name, boolean resolve)
        throws ClassNotFoundException
    {
		if (name.startsWith("java.")) {
			return super.loadClass(name, resolve); // prevent SecurityException
		}

		/*
			Check first for classes loaded through this loader.
			The VM will not allow a class to be loaded twice.
		*/
		Class c = findLoadedClass(name);
		if ( c != null ) {
			return c;
		}

		// This is copied from ClassManagerImpl
		// We should refactor this somehow if it sticks around
		if ( name.startsWith( ClassManagerImpl.BSH_PACKAGE ) ) {
			try {
				return bsh.Interpreter.class.getClassLoader().loadClass( name );
			} catch ( ClassNotFoundException e ) {
				// ignore
			}
		}

		/*
			Try to find the class using our classloading mechanism.
		*/
		c = findClass( name );

		if ( resolve ) {
			resolveClass( c );
		}

		return c;
	}

	/**
		Find the correct source for the class...

		Try designated loader if any
		Try our URLClassLoader paths if any
		Try base loader if any
		Try system ???
	*/
	// add some caching for not found classes?
	protected Class findClass( String name ) 
		throws ClassNotFoundException 
	{
		// Deal with this cast somehow... maybe have this class use 
		// ClassManagerImpl type directly.
		// Don't add the method to BshClassManager... it's really an impl thing
		ClassManagerImpl bcm = (ClassManagerImpl)getClassManager();

		// Should we try to load the class ourselves or delegate?
		// look for overlay loader

		// Deal with this cast somehow... maybe have this class use 
		// ClassManagerImpl type directly.
		// Don't add the method to BshClassManager... it's really an impl thing
		ClassLoader cl = bcm.getLoaderForClass( name );

		Class c;

		// If there is a designated loader and it's not us delegate to it
		if ( cl != null && cl != this )
			try {
				return cl.loadClass( name );
			} catch ( ClassNotFoundException e ) {
				throw new ClassNotFoundException(
					"Designated loader could not find class: "+e );
			}

		// Let URLClassLoader try any paths it may have
		if ( getURLs().length > 0 )
			try {
				return super.findClass(name);
			} catch ( ClassNotFoundException e ) { 
				//System.out.println(
				//	"base loader here caught class not found: "+name );
			}


		// If there is a baseLoader and it's not us delegate to it
		cl = bcm.getBaseLoader();

		if ( cl != null && cl != this )
			try {
				return cl.loadClass( name );
			} catch ( ClassNotFoundException e ) { }

		// Try system loader
		return bcm.plainClassForName( name );
	}

	/*
		The superclass does something like this

        c = findLoadedClass(name);
        if null
            try
                if parent not null
                    c = parent.loadClass(name, false);
                else
                    c = findBootstrapClass(name);
            catch ClassNotFoundException 
                c = findClass(name);
	*/

	BshClassManager getClassManager() { return classManager; }

}