servletloader.java

来自「很棒的web服务器源代码」· Java 代码 · 共 116 行

// ServletLoader.java
// $Id: ServletLoader.java,v 1.10 2000/08/16 21:37:45 ylafon Exp $
// (c) COPYRIGHT MIT and INRIA, 1996.
// Please first read the full copyright statement in file COPYRIGHT.html

package org.w3c.jigsaw.servlet;

import java.io.ByteArrayOutputStream;
import java.io.InputStream;
import java.io.PrintStream;

import java.net.URL;
import java.net.URLConnection;

import java.util.Hashtable;

/**
 * @author Alexandre Rafalovitch <[e-mail]>
 * @author Anselm Baird-Smith <[e-mail]>
 */

public class ServletLoader extends ClassLoader {
    private static final boolean debug = false;
    private Hashtable classes = null;

    RemoteServletWrapper wrapper = null;

    private void trace(String msg) {
	System.out.println("["+wrapper.getURLPath()+"]: "+msg);
    }

    /**
     * Given the class name, return its URL.
     * @param name The class to be loaded.
     * @return The URL for the class.
     */

    protected URL locateClass(String name) {
	String base = wrapper.getServletBase();
	try {
	    String cname = name.replace('.', '/')+".class";
	    return new URL(new URL(base), cname);
	} catch (Exception ex) {
	}
	return null;
    }

    /**
     * Try to load class.
     * @param name The class name.
     * @param boolean The resolve flag
     * @return a Class instance
     * @exception ClassNotFoundException if the class file can't be found.
     */
    protected Class loadClass(String name, boolean resolve)
	throws ClassNotFoundException
    {
	//remove the .class
	if (name.endsWith(".class"))
	    name = name.substring(0,name.lastIndexOf('.'));
	Class c = null;
	if ( debug )
	    trace("loading "+name);
	// Look for a cached class first:
	if ((c = (Class) classes.get(name)) != null) 
	    return c;
	SecurityManager s = System.getSecurityManager();
	if ( s != null ) {
	    int i = name.lastIndexOf('.');
	    if ( i >= 0 )
		s.checkPackageAccess(name.substring(0, i));
	}
	// Then look for a system class:
	try {
	    if ((c = findSystemClass(name)) != null)
		return c;
	} catch (Exception ex) {
	}
	// Load the class bytes from the net:
	byte data[] = null;
	URL  url    = locateClass(name);
	if ( url == null )
	    throw new ClassNotFoundException("invalid servlet base");
	if ( debug )
	    trace(name+" located at "+url);
	try {
	    URLConnection         conn  = url.openConnection();
	    InputStream           in    = conn.getInputStream();
	    ByteArrayOutputStream out   = new ByteArrayOutputStream(512);
	    byte                  buf[] = new byte[512];
	    for (int got = 0 ; (got = in.read(buf)) > 0 ; )
		out.write(buf, 0, got);
	    data = out.toByteArray();
	    in.close();
	} catch (Exception ex) {
	    ex.printStackTrace();
	    throw new ClassNotFoundException(url.toExternalForm());
	}
	// Define and resolve the class:
	c = defineClass(data, 0, data.length);
	if ( resolve )
	    resolveClass(c);
	classes.put(name, c);
	if ( debug )
	    trace(name+": loading done.");
	return c;
    }

    protected ServletLoader(RemoteServletWrapper wrapper) {
	super();
	this.wrapper = wrapper;
	this.classes = new Hashtable(13);
    }

}