shellcmds.java

有关java 的p2p应用,是一般很好的教程,有兴趣的朋友应该好好阅读一下

/*
 * Copyright (c) 2001 Sun Microsystems, Inc.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *       Sun Microsystems, Inc. for Project JXTA."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
 *
 * 4. The names "Sun", "Sun Microsystems, Inc.", "JXTA" and "Project JXTA" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact Project JXTA at http://www.jxta.org.
 *
 * 5. Products derived from this software may not be called "JXTA",
 *    nor may "JXTA" appear in their name, without prior written
 *    permission of Sun.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL SUN MICROSYSTEMS OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of Project JXTA.  For more
 * information on Project JXTA, please see
 * <http://www.jxta.org/>.
 *
 * This license is based on the BSD license adopted by the Apache Foundation.
 *
 * $Id: ShellCmds.java,v 1.20 2006/06/14 16:37:11 bondolo Exp $
 */


package net.jxta.impl.shell;

import java.net.*;
import java.util.*;
import java.util.zip.*;
import java.io.File;
import java.util.jar.JarFile;
import java.util.jar.JarEntry;

import java.io.IOException;
import java.lang.reflect.UndeclaredThrowableException;

import java.util.logging.Logger;
import java.util.logging.Level;

/**
 * This  class has methods for getting an array of all available Shell commands
 * and for instantiating of a specific Shell command (the standard constructor is used!).
 * It uses a ClassLoader that can load class-files from an arbirtrary number of jar-files.
 * The list of jar-files is encoded in the INST_JARS environment variable of the ShellApp
 * that instantiated this class.
 * The encoded String has following format:
 * <path1><PATH_SEPARATOR><path2><PATH_SEPARATOR>...
 *
 * Whenever a ShellApp needs access to the Shell commands this class should be used.
 * For example to get all available Shell commands use the following code:
 * <code>
 * 		ShellCmds cmds = new ShellCmds((ShellApp)this);
 *      String[] cmdList = cmds.list();
 * </code>
 * To instantiate a command you could use following code:
 * <code>
 *		// Instantiate the 'man' command.
 *		ShellApp app = cmds.getInstance("man");
 *		// Now set the group and the input and output pipes if neccessary.
 *		...
 *		// For example we want to print the short description of the app.
 *		println(app.getDescription());
 * </code>
 */
public final class ShellCmds {
    /** For debugging purposes. */
    private static final java.util.logging.Logger LOG = java.util.logging.Logger.getLogger(ShellCmds.class.getName());;
    
    /** Name of environment variable. */
    public static final String INST_JARS = "instjars";
    
    /** Char used to separate paths. */
    public static final String PATH_SEPARATOR = System.getProperty("path.separator");
    
    static final String BIN_PACKAGE = "net.jxta.impl.shell.bin";
    static final String BIN_PATH = "net/jxta/impl/shell/bin/";
    static final int BIN_PATH_LEN = BIN_PATH.length();
    
    /** Reference to the ShellApp that instantiated this class. */
    private final ShellEnv env;
    
    
    /**
     * Initializes a newly created ShellCmds object with a reference to the instantiating ShellApp.
     * This reference will be used to obtain its current ShellEnv object which serves for reading
     * and storing the INST_JARS environment variable.
     *
     * @param	env	the environment to use.
     */
    public ShellCmds(ShellEnv env) {
        this.env = env;
    }
    
    /**
     * Static method to extract the list of paths out of a String. The format of the String is:
     * <path1><PATH_SEPARATOR><path2>...
     * Only correct paths are added to the later returned list.
     *
     * @param	pathList	the String the paths will be extracted from.
     * @return	an array of all valid paths. If the given parameter contains no path or none
     *			of the given paths is valid then an empty list is returned.
     */
    public static URL [] parseClassPath( String pathList ) {
        
        List<URL> pathURLS = new ArrayList<URL>();
        
        StringTokenizer tok = new StringTokenizer( pathList, PATH_SEPARATOR, false );
        while (tok.hasMoreTokens()) {
            String fileName = tok.nextToken();
            File file = new File(fileName);
            try {
                pathURLS.add( file.toURL() );
            } catch( MalformedURLException bad ) {
                
            }
        }
        
        return pathURLS.toArray( new URL[pathURLS.size()] );
    }
    
    /**
     * Static method to encode a list of paths into its corresponding String representation.
     * The format of the String is: <path1><PATH_SEPARATOR><path2>...
     *
     * @param	pathList		the list of paths to be encoded.
     * @return	a String representation of the given list.
     */
    public static String encodeInstJars(List pathList) {
        StringBuffer buf = new StringBuffer();
        for (int i = 0, size = pathList.size(); i < size; i++) {
            buf.append(pathList.get(i));
            if (i < size - 1)
                buf.append(PATH_SEPARATOR);
        }
        return buf.toString();
    }
    
    /**
     * Stores the String representation of the given list of paths in the environment
     * of the ShellApp.
     *
     * @param	pathList	list of paths to be stored in the environment of the ShellApp.
     */
    public void setInstJars(List pathList) {
        // Convert list into its corresponding String representation,
        String instJars = encodeInstJars(pathList);
        // and set the new value of environment variable INST_JARS.
        env.add(INST_JARS, new ShellObject("Installed Jar Files", instJars));
    }
    
    /**
     * Retrieves the list of paths encoded as a String from the ShellApp's environment.
     *
     * @return	a list of path objects.
     */
    public URL [] getInstJars() {
        
        if (env.contains(INST_JARS)) {
            // If environment variable INST_JARS already exists, then
            // get environment variable INST_JARS, and
            // extract zip-files and directories and construct a list containing them.
            String instJars = (String)env.get(INST_JARS).getObject();
            return parseClassPath(instJars);
        } else {
            // else return an empty list.
            return new URL[0];
        }
    }
    
    /**
     * Returns an array of all available Shell commands.
     *
     * <p/>The current implementation tries to locate commands on the classpath
     * pf the classloader