JAVA NIO 服务器与客户端实现示例

公共类：

package com.stevex.app.nio;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.CharacterCodingException;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;

public class CharsetHelper {
private static final String UTF_8 = "UTF-8";
private static CharsetEncoder encoder = Charset.forName(UTF_8).newEncoder();
private static CharsetDecoder decoder = Charset.forName(UTF_8).newDecoder();

public static ByteBuffer encode(CharBuffer in) throws CharacterCodingException{
return encoder.encode(in);
}

public static CharBuffer decode(ByteBuffer in) throws CharacterCodingException{
return decoder.decode(in);
}
}
服务器代码：
package com.stevex.app.nio;

import java.io.IOException;
import java.net.InetSocketAddress;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.channels.ClosedChannelException;
import java.nio.channels.SelectionKey;
import java.nio.channels.Selector;
import java.nio.channels.ServerSocketChannel;
import java.nio.channels.SocketChannel;
import java.util.Iterator;

public class XiaoNa {
private ByteBuffer readBuffer;
private Selector selector;

public static void main(String[] args){
XiaoNa xiaona = new XiaoNa();
xiaona.init();
xiaona.listen();
}

private void init(){
readBuffer = ByteBuffer.allocate(1024);
ServerSocketChannel servSocketChannel;

try {
servSocketChannel = ServerSocketChannel.open();
servSocketChannel.configureBlocking(false);
//绑定端口
servSocketChannel.socket().bind(new InetSocketAddress(8383));

selector = Selector.open();
servSocketChannel.register(selector, SelectionKey.OP_ACCEPT);
} catch (IOException e) {
e.printStackTrace();
}
}

private void listen() {
while(true){
try{
selector.select();
Iterator ite = selector.selectedKeys().iterator();

while(ite.hasNext()){
SelectionKey key = (SelectionKey) ite.next();
ite.remove();//确保不重复处理

handleKey(key);
}
}
catch(Throwable t){
t.printStackTrace();
}
}
}

private void handleKey(SelectionKey key)
throws IOException, ClosedChannelException {
SocketChannel channel = null;

try{
if(key.isAcceptable()){
ServerSocketChannel serverChannel = (ServerSocketChannel) key.channel();
channel = serverChannel.accept();//接受连接请求
channel.configureBlocking(false);
channel.register(selector, SelectionKey.OP_READ);
}
else if(key.isReadable()){
channel = (SocketChannel) key.channel();
readBuffer.clear();
/*当客户端channel关闭后，会不断收到read事件，但没有消息，即read方法返回-1
* 所以这时服务器端也需要关闭channel，避免无限无效的处理*/
int count = channel.read(readBuffer);

if(count > 0){
//一定需要调用flip函数，否则读取错误数据
readBuffer.flip();
/*使用CharBuffer配合取出正确的数据
String question = new String(readBuffer.array());
可能会出错，因为前面readBuffer.clear();并未真正清理数据
只是重置缓冲区的position, limit, mark，
而readBuffer.array()会返回整个缓冲区的内容。
decode方法只取readBuffer的position到limit数据。
例如，上一次读取到缓冲区的是"where", clear后position为0，limit为 1024，
再次读取“bye"到缓冲区后，position为3，limit不变，
flip后position为0，limit为3，前三个字符被覆盖了，但"re"还存在缓冲区中，
所以 new String(readBuffer.array()) 返回 "byere",
而decode(readBuffer)返回"bye"。
*/
CharBuffer charBuffer = CharsetHelper.decode(readBuffer);
String question = charBuffer.toString();
String answer = getAnswer(question);
channel.write(CharsetHelper.encode(CharBuffer.wrap(answer)));
}
else{
//这里关闭channel，因为客户端已经关闭channel或者异常了
channel.close();
}
}
}
catch(Throwable t){
t.printStackTrace();
if(channel != null){
channel.close();
}
}
}

private String getAnswer(String question){
String answer = null;

switch(question){
case "who":
answer = "我是小娜\n";
break;
case "what":
answer = "我是来帮你解闷的\n";
break;
case "where":
answer = "我来自外太空\n";
break;
case "hi":
answer = "hello\n";
break;
case "bye":
answer = "88\n";
break;
default:
answer = "请输入 who， 或者what， 或者where";
}

return answer;
}
}
客户端代码：
package com.stevex.app.nio;

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.SocketChannel;
import java.util.Iterator;
import java.util.Random;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.TimeUnit;

public class Client implements Runnable{
private BlockingQueue<String> words;
private Random random;

public static void main(String[] args) {
//种多个线程发起Socket客户端连接请求
for(int i=0; i<10; i++){
Client c = new Client();
c.init();
new Thread(c).start();
}
}

@Override
public void run() {
SocketChannel channel = null;
Selector selector = null;
try {
channel = SocketChannel.open();
channel.configureBlocking(false);
//请求连接
channel.connect(new InetSocketAddress("localhost", 8383));
selector = Selector.open();
channel.register(selector, SelectionKey.OP_CONNECT);
boolean isOver = false;

while(! isOver){
selector.select();
Iterator ite = selector.selectedKeys().iterator();
while(ite.hasNext()){
SelectionKey key = (SelectionKey) ite.next();
ite.remove();

if(key.isConnectable()){
if(channel.isConnectionPending()){
if(channel.finishConnect()){
//只有当连接成功后才能注册OP_READ事件
key.interestOps(SelectionKey.OP_READ);

channel.write(CharsetHelper.encode(CharBuffer.wrap(getWord())));
sleep();
}
else{
key.cancel();
}
}
}
else if(key.isReadable()){
ByteBuffer byteBuffer = ByteBuffer.allocate(128);
channel.read(byteBuffer);
byteBuffer.flip();
CharBuffer charBuffer = CharsetHelper.decode(byteBuffer);
String answer = charBuffer.toString();
System.out.println(Thread.currentThread().getId() + "---" + answer);

String word = getWord();
if(word != null){
channel.write(CharsetHelper.encode(CharBuffer.wrap(word)));
}
else{
isOver = true;
}
sleep();
}
}
}
} catch (IOException e) {
e.printStackTrace();
}
finally{
if(channel != null){
try {
channel.close();
} catch (IOException e) {
e.printStackTrace();
}
}

if(selector != null){
try {
selector.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}

private void init() {
words = new ArrayBlockingQueue<String>(5);
try {
words.put("hi");
words.put("who");
words.put("what");
words.put("where");
words.put("bye");
} catch (InterruptedException e) {
e.printStackTrace();
}

random = new Random();
}

private String getWord(){
return words.poll();
}

private void sleep() {
try {
TimeUnit.SECONDS.sleep(random.nextInt(3));
} catch (InterruptedException e) {
e.printStackTrace();
}
}

private void sleep(long l) {
try {
TimeUnit.SECONDS.sleep(l);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}