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电梯直达

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发表于 2012-07-15 21:25 |只看该作者 |倒序浏览

Java网络编程精解书中4.4.2中的例子。非阻塞模式的client用来selector，但是我加了打印发现该selector一直会返回isWritable的key，请问这是什么缘故。
client代码

package com.nonblock.test;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;
public class EchoClient{
private SocketChannel socketChannel = null;
private ByteBuffer sendBuffer=ByteBuffer.allocate(1024);
private ByteBuffer receiveBuffer=ByteBuffer.allocate(1024);
private Charset charset=Charset.forName("GBK");
private Selector selector;
public EchoClient()throws IOException{
socketChannel = SocketChannel.open();
InetAddress ia = InetAddress.getLocalHost();
InetSocketAddress isa = new InetSocketAddress(ia,8000);
socketChannel.connect(isa);
socketChannel.configureBlocking(false);
System.out.println("与服务器的连接建立成功");
selector=Selector.open();
}
public static void main(String args[])throws IOException{
final EchoClient client=new EchoClient();
Thread receiver=new Thread(){
public void run(){
client.receiveFromUser();
}
};
receiver.start();
client.talk();
}
public void receiveFromUser(){
try{
BufferedReader localReader=new BufferedReader(new InputStreamReader(System.in));
String msg=null;
while((msg=localReader.readLine())!=null){
synchronized(sendBuffer){
System.out.println("receive from user");
sendBuffer.put(encode(msg + "\r\n"));
}
if(msg.equals("bye"))
break;
}
}catch(IOException e){
e.printStackTrace();
}
}
public void talk()throws IOException {
socketChannel.register(selector,
SelectionKey.OP_READ |
SelectionKey.OP_WRITE);
while (selector.select() > 0 ){
Set readyKeys = selector.selectedKeys();
Iterator it = readyKeys.iterator();
while (it.hasNext()){
SelectionKey key=null;
try{
key = (SelectionKey) it.next();
it.remove();
if (key.isReadable()) {
System.out.println("触发可读监听");
receive(key);
}
if (key.isWritable()) {
System.out.println("触发可写监听");//此处是我加的打印！！！！！！！！！！！！！！
send(key);
}
}catch(IOException e){
e.printStackTrace();
try{
if(key!=null){
key.cancel();
key.channel().close();
}
}catch(Exception ex){e.printStackTrace();}
}
}//#while
}//#while
}
public void send(SelectionKey key)throws IOException{
SocketChannel socketChannel=(SocketChannel)key.channel();
synchronized(sendBuffer){
sendBuffer.flip(); //把极限设为位置
//System.out.println(sendBuffer.toString());
int ret = socketChannel.write(sendBuffer);
//System.out.println("ret = " + ret);
sendBuffer.compact();
}
}
public void receive(SelectionKey key)throws IOException{
SocketChannel socketChannel=(SocketChannel)key.channel();
socketChannel.read(receiveBuffer);
receiveBuffer.flip();
String receiveData=decode(receiveBuffer);
if(receiveData.indexOf("\n")==-1)return;
String outputData=receiveData.substring(0,receiveData.indexOf("\n")+1);
System.out.print(outputData);
if(outputData.equals("echo:bye\r\n")){
key.cancel();
socketChannel.close();
System.out.println("关闭与服务器的连接");
selector.close();
System.exit(0);
}
ByteBuffer temp=encode(outputData);
receiveBuffer.position(temp.limit());
receiveBuffer.compact();
}
public String decode(ByteBuffer buffer){ //解码
CharBuffer charBuffer= charset.decode(buffer);
return charBuffer.toString();
}
public ByteBuffer encode(String str){ //编码
return charset.encode(str);
}
}
/****************************************************
* 作者：孙卫琴 *
* 来源：<<Java网络编程精解>> *
* 技术支持网址：www.javathinker.org *
***************************************************/

复制代码

server的代码：

package com.nonblock.test;
import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.nio.charset.Charset;
import java.util.Iterator;
import java.util.Set;
public class EchoServer{
private Selector selector = null;
private ServerSocketChannel serverSocketChannel = null;
private int port = 8000;
private Charset charset=Charset.forName("GBK");
public EchoServer()throws IOException{
selector = Selector.open();
serverSocketChannel= ServerSocketChannel.open();
serverSocketChannel.socket().setReuseAddress(true);
serverSocketChannel.configureBlocking(false);
serverSocketChannel.socket().bind(new InetSocketAddress(port));
System.out.println("服务器启动");
}
public void service() throws IOException{
serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT );
while (selector.select() > 0 ){
Set readyKeys = selector.selectedKeys();
Iterator it = readyKeys.iterator();
while (it.hasNext()){
SelectionKey key=null;
try{
key = (SelectionKey) it.next();
it.remove();
if (key.isAcceptable()) {
ServerSocketChannel ssc = (ServerSocketChannel) key.channel();
SocketChannel socketChannel = (SocketChannel) ssc.accept();
System.out.println("接收到客户连接，来自:" +
socketChannel.socket().getInetAddress() +
":" + socketChannel.socket().getPort());
socketChannel.configureBlocking(false);
ByteBuffer buffer = ByteBuffer.allocate(1024);
socketChannel.register(selector,
SelectionKey.OP_READ |
SelectionKey.OP_WRITE, buffer);
}
if (key.isReadable()) {
receive(key);
}
if (key.isWritable()) {
send(key);
}
}catch(IOException e){
e.printStackTrace();
try{
if(key!=null){
key.cancel();
key.channel().close();
}
}catch(Exception ex){e.printStackTrace();}
}
}//#while
}//#while
}
public void send(SelectionKey key)throws IOException{
ByteBuffer buffer=(ByteBuffer)key.attachment();
SocketChannel socketChannel=(SocketChannel)key.channel();
buffer.flip(); //把极限设为位置，把位置设为0
String data=decode(buffer);
if(data.indexOf("\r\n")==-1)return;
String outputData=data.substring(0,data.indexOf("\n")+1);
System.out.print(outputData);
ByteBuffer outputBuffer=encode("echo:"+outputData);
while(outputBuffer.hasRemaining())
socketChannel.write(outputBuffer);
ByteBuffer temp=encode(outputData);
buffer.position(temp.limit());
buffer.compact();
if(outputData.equals("bye\r\n")){
key.cancel();
socketChannel.close();
System.out.println("关闭与客户的连接");
}
}
public void receive(SelectionKey key)throws IOException{
ByteBuffer buffer=(ByteBuffer)key.attachment();
SocketChannel socketChannel=(SocketChannel)key.channel();
ByteBuffer readBuff= ByteBuffer.allocate(32);
socketChannel.read(readBuff);
readBuff.flip();
buffer.limit(buffer.capacity());
buffer.put(readBuff);
}
public String decode(ByteBuffer buffer){ //解码
CharBuffer charBuffer= charset.decode(buffer);
return charBuffer.toString();
}
public ByteBuffer encode(String str){ //编码
return charset.encode(str);
}
public static void main(String args[])throws Exception{
EchoServer server = new EchoServer();
server.service();
}
}
/****************************************************
* 作者：孙卫琴 *
* 来源：<<Java网络编程精解>> *
* 技术支持网址：www.javathinker.org *
***************************************************/

复制代码

运行结果：
client：
触发可写监听
触发可写监听
触发可写监听
触发可写监听
触发可写监听
触发可写监听
触发可写监听
触发可写监听
触发可写监听
触发可写监听

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