用java nio模擬下載服務

/**

 * Fly_m at 2009-5-20

 */

package com.m_ylf.study.nio;

 

import java.io.File;

import java.io.FileInputStream;

import java.net.InetSocketAddress;

import java.nio.ByteBuffer;

import java.nio.channels.*;

import java.util.HashMap;

import java.util.Iterator;

import java.util.Map;

import java.util.concurrent.Callable;

 

/** @author Fly_m */

//模擬下載服務

public class DownloadServer<T> implements Callable<T>{

private Selector selector;//創建全局selector

private Map<SocketChannel, Handle> map = new HashMap<SocketChannel, Handle>();//socketChannel和handle之間的映射

 

//創建一個服務器serverSocketChannel,並與selector進行註冊

public DownloadServer() throws Exception {

selector = Selector.open();

ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

serverSocketChannel.configureBlocking(false);

serverSocketChannel.socket().bind(new InetSocketAddress(1234));

serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);

}

 

//對selector.select進行迭代,並依次進行處理

public T call() throws Exception {

System.out.println("startTo listen in 1234....");

for(; ;) {

selector.select();

Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();

while(keyIterator.hasNext()) {

SelectionKey key = keyIterator.next();

if(key.isValid())

handle(key);

keyIterator.remove();

}

}

}

 

//處理每個key,對於acceptable的key,由主類進行處理,而其他事件,則由內部類進行處理

private void handle(final SelectionKey key) throws Exception {

if(key.isAcceptable()) {

ServerSocketChannel channel = (ServerSocketChannel) key.channel();

SocketChannel socketChannel = channel.accept();

socketChannel.configureBlocking(false);

socketChannel.register(selector, SelectionKey.OP_READ);//註冊讀事件

map.put(socketChannel, new Handle());//把socket和handle進行綁定

}

//用map中的handle處理read和write事件,以模擬多個文件同時進行下載

if(key.isReadable() || key.isWritable()) {

SocketChannel socketChannel = (SocketChannel) key.channel();

final Handle handle = map.get(socketChannel);

if(handle != null)

handle.handle(key);

}

}

 

//內部類,模擬一個內部類處理一個文件下載服務,多個類可以處理多個文件下載服務

private class Handle{

private StringBuilder message;

private boolean writeOK = true;

private ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

private FileChannel fileChannel;

private String fileName;

 

private void handle(SelectionKey key) throws Exception {

if(key.isReadable()) {

SocketChannel socketChannel = (SocketChannel) key.channel();

if(writeOK)

message = new StringBuilder();

while(true) {

byteBuffer.clear();

int r = socketChannel.read(byteBuffer);

if(r == 0)

break;

if(r == -1) {

socketChannel.close();

key.cancel();

return;

}

message.append(new String(byteBuffer.array(), 0, r));

}

//將接收到的信息轉化成文件名,以映射到服務器上的指定文件

if(writeOK && invokeMessage(message)) {

socketChannel.register(selector, SelectionKey.OP_WRITE);

writeOK = false;

}

}

//向客戶端寫數據

if(key.isWritable()) {

if(!key.isValid())

return;

SocketChannel socketChannel = (SocketChannel) key.channel();

if(fileChannel == null)

fileChannel = new FileInputStream(fileName).getChannel();

byteBuffer.clear();

int w = fileChannel.read(byteBuffer);

//如果文件已寫完,則關掉key和socket

if(w <= 0) {

fileName = null;

fileChannel.close();

fileChannel = null;

writeOK = true;

socketChannel.close();

key.channel();

return;

}

byteBuffer.flip();

socketChannel.write(byteBuffer);

}

}

 

//將信息轉化成文件名

private boolean invokeMessage(StringBuilder message) {

String m = message.toString();

try {

File f = new File(m);

if(!f.exists())

return false;

fileName = m;

return true;

} catch(Exception e) {

return false;

}

}

 

}

 

public static void main(String[] args) throws Exception {

/*

ExecutorService executorService = Executors.newSingleThreadExecutor();

executorService.submit(new DownloadServer<Object>());

executorService.shutdown();

*/

new DownloadServer().call();

}

}

/**

 * Fly_m at 2009-5-20

 */

package com.m_ylf.study.nio;

import java.io.RandomAccessFile;

import java.nio.ByteBuffer;

import java.nio.channels.FileChannel;

import java.nio.channels.SelectionKey;

import java.nio.channels.Selector;

import java.nio.channels.SocketChannel;

import java.util.Iterator;

import java.util.concurrent.Callable;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.net.InetSocketAddress;

/** @author Fly_m */

//模擬下載客戶端

public class DownloadClient<T> implements Callable<T>{

private FileChannel fileChannel;

private static Selector selector;

private ByteBuffer byteBuffer = ByteBuffer.allocate(1024);

private String serverFileName;//服務器上的文件

private String localFileName;//下載到客戶端的文件名

public DownloadClient(String serverFileName, String localFileName) {

this.serverFileName = serverFileName;

this.localFileName = localFileName;

}

public T call() throws Exception {

//開啓selector,並建立socket到指定端口的連接

if(selector == null)

selector = Selector.open();

SocketChannel channel = SocketChannel.open();

channel.configureBlocking(false);

channel.connect(new InetSocketAddress("localhost", 1234));

channel.register(selector, SelectionKey.OP_CONNECT);

//進行信息讀取

for(; ;) {

selector.select();

Iterator<SelectionKey> keyIterator = selector.selectedKeys().iterator();

while(keyIterator.hasNext()) {

SelectionKey key = keyIterator.next();

keyIterator.remove();

//連接事件

if(key.isConnectable()) {

SocketChannel socketChannel = (SocketChannel) key.channel();

if(socketChannel.isConnectionPending())

socketChannel.finishConnect();

socketChannel.write(ByteBuffer.wrap(serverFileName.getBytes()));//向服務器發信息,信息中即服務器上的文件名

socketChannel.register(selector, SelectionKey.OP_READ);

}

//讀事件

if(key.isReadable()) {

SocketChannel socketChannel = (SocketChannel) key.channel();

byteBuffer.clear();

if(!socketChannel.isConnected())

return null;

//向本機下載文件創建文件channel

if(fileChannel == null)

fileChannel = new RandomAccessFile(localFileName, "rw").getChannel();

int r = socketChannel.read(byteBuffer);

//如果文件下載完畢,則關掉channel,同時關掉socketChannel

if(r <= 0) {

if(fileChannel != null)

fileChannel.close();

channel.close();

key.cancel();

return null;

}

byteBuffer.flip();

//寫到下載文件中

fileChannel.write(byteBuffer);

}

}

}

}

//客戶端用10個線程向服務器端下載文件,並保存爲不同的文件

public static void main(String[] args) throws Exception {

ExecutorService executorService = Executors.newSingleThreadExecutor();

for(int i = 0; i < 10; i++) {

executorService.submit(new DownloadClient<Object>("d:/log4j.log", "d:/down" + i + ".log"));

}

executorService.shutdown();

}

}