CD Actual 25/CDROM25.iso/Share/prog/VJ11/VJTRIAL.EXE/IE30Java.exe/classd.exe/sun/applet/AppletClassLoader.java

Java Source | 1997-01-27 | 5.3 KB | 196 lines

/*
 * @(#)AppletClassLoader.java    1.25 96/03/25
 *
 * Copyright (c) 1994-1996 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Permission to use, copy, modify, and distribute this software
 * and its documentation for NON-COMMERCIAL purposes and without
 * fee is hereby granted provided that this copyright notice
 * appears in all copies. Please refer to the file "copyright.html"
 * for further important copyright and licensing information.
 *
 * SUN MAKES NO REPRESENTATIONS OR WARRANTIES ABOUT THE SUITABILITY OF
 * THE SOFTWARE, EITHER EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED
 * TO THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE, OR NON-INFRINGEMENT. SUN SHALL NOT BE LIABLE FOR
 * ANY DAMAGES SUFFERED BY LICENSEE AS A RESULT OF USING, MODIFYING OR
 * DISTRIBUTING THIS SOFTWARE OR ITS DERIVATIVES.
 */

package sun.applet;

import java.util.Hashtable;
import java.io.InputStream;
import java.io.IOException;
import java.io.FileNotFoundException;
import java.net.URL;
import java.net.URLConnection;
import java.net.MalformedURLException;
import sun.misc.MessageUtils;

/**
 * This class defines an applet class loader.
 *
 * @version     1.25, 03/25/96
 * @author     Arthur van Hoff
 */
class AppletClassLoader extends ClassLoader {
    boolean verboseClassLoading = false;

    Hashtable classes = new Hashtable();
    URL base;

    /**
     * Load applets from a base URL.
     */
    AppletClassLoader(URL base) {
    this.base = base;
    }

    /**
     * Load a class from a URL.
     */
    private Class loadClass(URL url) throws IOException {
    InputStream in = null;
    try {
        try {
        URLConnection c = url.openConnection();
        c.setAllowUserInteraction(false);
        in = c.getInputStream();

        int len = c.getContentLength();
        byte data[] = new byte[(len == -1) ? 4096 : len];
        int total = 0, n;

        Thread thread = Thread.currentThread();

        while (((n = in.read(data, total, data.length - total)) >= 0) && !thread.isInterrupted()) {
            if ((total += n) == data.length) {
            if (len < 0) {
                byte newdata[] = new byte[total * 2];
                System.arraycopy(data, 0, newdata, 0, total);
                data = newdata;
            } else {
                break;
            }
            }
        }
        if (thread.isInterrupted()) {
            throw new IOException("class loading interrupted: " + url);
        }

        return defineClass(data, 0, total);
        } finally {
        if (in != null) {
            in.close();
        }
        }
    } catch (IOException e) {
        e.printStackTrace();
        throw e;
    } catch (Throwable e) {
        e.printStackTrace();
        throw new IOException("class not loaded: " + url);
    }
    }

    /**
     * Load a class from this class loader.
     */
    public Class loadClass(String name) throws ClassNotFoundException {
    return loadClass(name, true);
    }

    /**
     * Load and resolve a class.
     */
    protected Class loadClass(String name, boolean resolve) throws ClassNotFoundException {
    Class cl = (Class)classes.get(name);
    if (cl == null) {
        SecurityManager security = System.getSecurityManager();
        if (security != null) {
        int i = name.lastIndexOf('.');
        if (i >= 0) {
            security.checkPackageAccess(name.substring(0, i));
        }
        }
        try {
        return findSystemClass(name);
        } catch (Throwable e) {
        }

        cl = findClass(name);
    }
    if (cl == null) {
        throw new ClassNotFoundException(name);
    }
    if (resolve) {
        resolveClass(cl);
    }
    return cl;
    }

    void errorMsg(String key, String arg) {
    System.err.println(MessageUtils.substProp("appletloader."+key,
                          arg));
    }

    void errorMsg(String key, String arg1, String arg2) {
    System.err.println(MessageUtils.substProp("appletloader."+key,
                          arg1, arg2));
    }

    /**
     * This method finds a class. The returned class
     * may be unresolved. This method has to be synchronized
     * to avoid two threads loading the same class at the same time.
     * Must be called with the actual class name.
     */
    private synchronized Class findClass(String name) {
    Class cl = (Class)classes.get(name);
    if (cl != null) {
        return cl;
    }

    if (verboseClassLoading)
        System.out.println(Thread.currentThread().getName() + " find class " + name);

    SecurityManager security = System.getSecurityManager();
    if (security != null) {
        int i = name.lastIndexOf('.');
        if (i >= 0) {
        security.checkPackageDefinition(name.substring(0, i));
        }
    }

    String cname = name.replace('.', '/') + ".class";

    try {
        URL url = new URL(base, cname);
        if (verboseClassLoading)
            System.out.println("Opening stream to: " + url + " to get " + name);
        cl = loadClass(url);
        if (!name.equals(cl.getName())) {
        Class oldcl = cl;
        cl = null;
        throw new ClassFormatError(name + " != " + oldcl.getName());
        }
        classes.put(name, cl);
    } catch (FileNotFoundException e) {
        errorMsg("filenotfound", name);
    } catch (ClassFormatError e) {
        errorMsg("fileformat", name);
    } catch (IOException e) {
        errorMsg("fileioexception", name);
    } catch (Exception e) {
        errorMsg("fileexception", e.toString(), name);
    } catch (ThreadDeath e) {
        errorMsg("filedeath", name);
        throw e;
    } catch (Error e) {
        errorMsg("fileerror", e.toString(), name);
    }
    return cl;
    }
}