more.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: more.java,v 1.17 2004/05/28 19:24:56 bondolo Exp $
 */

package net.jxta.impl.shell.bin.more;

import java.util.Collections;
import java.util.StringTokenizer;

import java.io.IOException;

import net.jxta.document.AdvertisementFactory;
import net.jxta.id.IDFactory;
import net.jxta.peergroup.PeerGroup;
import net.jxta.pipe.InputPipe;
import net.jxta.pipe.OutputPipe;
import net.jxta.pipe.PipeService;
import net.jxta.protocol.PipeAdvertisement;

import net.jxta.impl.shell.GetOpt;
import net.jxta.impl.shell.ShellApp;
import net.jxta.impl.shell.ShellEnv;
import net.jxta.impl.shell.ShellObject;

/**
 *  Pages through output.
 **/
public class more extends ShellApp {
    
    private final static int MAX_CONSOLE = 20;
    
    private int count = 0;
    
    /**
     *  {@inheritDoc}
     **/
    public int startApp( final String[] args) {
        ShellEnv env = getEnv();
        boolean pretty = false;
        
        try {
            GetOpt options = new GetOpt( args, 0, "p" );
            
            while( true ) {
            int option;
            try {
                option = options.getNextOption();
            } catch( IllegalArgumentException badopt ) {
                consoleMessage( "Illegal argument :" + badopt );
                return syntaxError();
            }
                            
                if( -1 == option ) {
                    break;
                }
                
                switch( option ) {
                    
                    case 'p' :
                        pretty = true;
                        break;
                        
                    default :
                        consoleMessage( "Unrecognized option" );
                        return syntaxError();
                }
            }
            
            String name = options.getNextParameter();
            
            if ( (null != name) && (null != options.getNextParameter()) ) {
                consoleMessage( "Unsupported parameter" );
                return syntaxError();
            }
            
            if( null != name ) {
                ShellObject obj = env.get(name);
                if (obj == null) {
                    consoleMessage( "Cannot access '" + name + "'" );
                    return ShellApp.appMiscError;
                }
                
                ShellEnv catEnv = new ShellEnv(env);
                
                
                PeerGroup current = (PeerGroup) getEnv().get("stdgroup").getObject();
                
                PipeService pipes = current.getPipeService();
                
                /*
                 *  create pipe to link the two
                 */
                PipeAdvertisement padv = null;
                
                try {
                    padv = (PipeAdvertisement)
                    AdvertisementFactory.newAdvertisement(
                    PipeAdvertisement.getAdvertisementType());
                    padv.setPipeID(IDFactory.newPipeID(current.getPeerGroupID()));
                    padv.setType(PipeService.UnicastType);
                    
                    InputPipe inpipe = pipes.createInputPipe(padv);
                    setInputPipe( inpipe );
                    env.add( "stdin", new ShellObject("Default InputPipe", inpipe) );

                    OutputPipe outpipe = pipes.createOutputPipe(padv, Collections.singleton(getGroup().getPeerID()), 1000 );
                    catEnv.add( "stdout", new ShellObject("Default OutputPipe", outpipe) );
                } catch (IOException ex) {
                    printStackTrace("Could not construct pipes for piped command.", ex);
                }
                
                final ShellApp chainCat = loadApp( null, "cat", catEnv );
                
                Thread catThread = new Thread() {
                    public void run() {
                        exec( chainCat, args );
                    }
                };
                
                setJoinedThread( catThread );
                catThread.start();
            }
            
            moreStdin();
            
            return ShellApp.appNoError;
        } catch (Exception ex) {
            printStackTrace( "Error processing commands", ex );
            return ShellApp.appMiscError;
        }
    }
    
    private void moreStdin() {
        
        do {
            String entry = null;
            try {
                entry = waitForInput() ;
            } catch( IOException failed ) { 
                printStackTrace( "whoops", failed );
            }
            
            if (entry == null)
                break;
            pagein(entry);
        } while( true );
    }
    
    private void pagein(String data) {
        
        StringTokenizer tokens = new StringTokenizer(data,"\n");
        String line = null;
        
        while (tokens.hasMoreElements()) {
            println(tokens.nextToken());
            count++;
            if( count >= MAX_CONSOLE ) {
                // reset the counter since we exited
                count = 0;
                print("-----More-----");
                String entry = null ;
                try {
                    entry = consWaitForInput();
                } catch( IOException failed ) { ; }
                if ( (entry == null) || entry.equals("q") )
                    return;
            }
        }
    }
    
    /**
     *  {@inheritDoc}
     **/
    public String getDescription() {
        return "Page through a Shell object or from standard input.";
    }
    
    private int syntaxError() {
        consoleMessage( "more [-p] [<env>]" );
        return ShellApp.appParamError;
    }
    
    /**
     *  {@inheritDoc}
     **/
    public void help() {
        println("NAME");
        println("     more  - " + getDescription() );
        println(" ");
        println("SYNOPSIS");
        println(" ");
        println("     more [-p] [<env>]" );
        println(" ");
        println("OPTIONS");
        println(" ");
        println("     [-p]    Pretty print the object." );
        println(" ");
        println("PARAMETERS");
        println(" ");
        println("     <env>   The environment variable to print." );
        println(" ");
        println("DESCRIPTION");
        println(" ");
        println("'more' is a Shell command that pages through the content ");
        println("of an object stored in environment variable. The name of the");
        println("is provided as an argument. If no argument is supplied, the");
        println("command takes its input from the 'stdin' shell pipe.");
        println(" ");
        println("EXAMPLE");
        println(" ");
        println("    JXTA> cat myfile | more");
        println(" ");
        println("This command pipes the content of the variable 'myfile' into the");
        println("'more' command and displays it to the Shell console.");
        println(" ");
        println("SEE ALSO");
        println(" ");
        println("    cat env");
        println(" ");
    }
}