http://blog.csdn.net/kongxx/article/details/7288896
Java Socket实战之一 单线程通信
Java Socket实战之二 多线程通信
Java Socket实战之三 传输对象
Java Socket实战之四 传输压缩对象
Java Socket实战之五 使用加密协议传输对象
前面几篇文章介绍了使用java.io和java.net类库实现的Socket通信，下面介绍一下使用java.nio类库实现的Socket。
java.nio包是Java在1.4之后增加的，用来提高I/O操作的效率。在nio包中主要包括以下几个类或接口:
* Buffer：缓冲区，用来临时存放输入或输出数据。
* Charset：用来把Unicode字符编码和其它字符编码互转。
* Channel：数据传输通道，用来把Buffer中的数据写入到数据源，或者把数据源中的数据读入到Buffer。
* Selector：用来支持异步I/O操作，也叫非阻塞I/O操作。
nio包中主要通过下面两个方面来提高I/O操作效率:
* 通过Buffer和Channel来提高I/O操作的速度。
* 通过Selector来支持非阻塞I/O操作。
下面来看一下程序中是怎么通过这些类库实现Socket功能。
首先介绍一下几个辅助类
辅助类SerializableUtil，这个类用来把java对象序列化成字节数组，或者把字节数组反序列化成java对象。
package com.googlecode.garbagecan.test.socket;import java.io.ByteArrayInputStream;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.io.ObjectInputStream;import java.io.ObjectOutputStream;public class SerializableUtil {public static byte[] toBytes(Object object) {ByteArrayOutputStream baos = new ByteArrayOutputStream();ObjectOutputStream oos = null;try {oos = new ObjectOutputStream(baos);oos.writeObject(object);byte[] bytes = baos.toByteArray();return bytes;} catch(IOException ex) {throw new RuntimeException(ex.getMessage(), ex);} finally {try {oos.close();} catch (Exception e) {}}}public static Object toObject(byte[] bytes) {ByteArrayInputStream bais = new ByteArrayInputStream(bytes);ObjectInputStream ois = null;try {ois = new ObjectInputStream(bais);Object object = ois.readObject();return object;} catch(IOException ex) {throw new RuntimeException(ex.getMessage(), ex);} catch(ClassNotFoundException ex) {throw new RuntimeException(ex.getMessage(), ex);} finally {try {ois.close();} catch (Exception e) {}}}}
辅助类MyRequestObject和MyResponseObject，这两个类是普通的java对象，实现了Serializable接口。MyRequestObject类是Client发出的请求，MyResponseObject是Server端作出的响应。
package com.googlecode.garbagecan.test.socket.nio;import java.io.Serializable;public class MyRequestObject implements Serializable {private static final long serialVersionUID = 1L;private String name;private String value;private byte[] bytes;public MyRequestObject(String name, String value) {this.name = name;this.value = value;this.bytes = new byte[1024];}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getValue() {return value;}public void setValue(String value) {this.value = value;}@Overridepublic String toString() {StringBuffer sb = new StringBuffer();sb.append("Request [name: " + name + ", value: " + value + ", bytes: " + bytes.length+ "]");return sb.toString();}}package com.googlecode.garbagecan.test.socket.nio;import java.io.Serializable;public class MyResponseObject implements Serializable {private static final long serialVersionUID = 1L;private String name;private String value;private byte[] bytes;public MyResponseObject(String name, String value) {this.name = name;this.value = value;this.bytes = new byte[1024];}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getValue() {return value;}public void setValue(String value) {this.value = value;}@Overridepublic String toString() {StringBuffer sb = new StringBuffer();sb.append("Response [name: " + name + ", value: " + value + ", bytes: " + bytes.length+ "]");return sb.toString();}}
下面主要看一下Server端的代码，其中有一些英文注释对理解代码很有帮助，注释主要是来源jdk的文档和例子，这里就没有再翻译
package com.googlecode.garbagecan.test.socket.nio;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;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;import java.util.logging.Level;import java.util.logging.Logger;import com.googlecode.garbagecan.test.socket.SerializableUtil;public class MyServer3 {private final static Logger logger = Logger.getLogger(MyServer3.class.getName());public static void main(String[] args) {Selector selector = null;ServerSocketChannel serverSocketChannel = null;try {// Selector for incoming time requestsselector = Selector.open();// Create a new server socket and set to non blocking modeserverSocketChannel = ServerSocketChannel.open();serverSocketChannel.configureBlocking(false);// Bind the server socket to the local host and portserverSocketChannel.socket().setReuseAddress(true);serverSocketChannel.socket().bind(new InetSocketAddress(10000));// Register accepts on the server socket with the selector. This// step tells the selector that the socket wants to be put on the// ready list when accept operations occur, so allowing multiplexed// non-blocking I/O to take place.serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT);// Here's where everything happens. The select method will// return when any operations registered above have occurred, the// thread has been interrupted, etc.while (selector.select() > 0) {// Someone is ready for I/O, get the ready keysIterator<SelectionKey> it = selector.selectedKeys().iterator();// Walk through the ready keys collection and process date requests.while (it.hasNext()) {SelectionKey readyKey = it.next();it.remove();// The key indexes into the selector so you// can retrieve the socket that's ready for I/Oexecute((ServerSocketChannel) readyKey.channel());}}} catch (ClosedChannelException ex) {logger.log(Level.SEVERE, null, ex);} catch (IOException ex) {logger.log(Level.SEVERE, null, ex);} finally {try {selector.close();} catch(Exception ex) {}try {serverSocketChannel.close();} catch(Exception ex) {}}}private static void execute(ServerSocketChannel serverSocketChannel) throws IOException {SocketChannel socketChannel = null;try {socketChannel = serverSocketChannel.accept();MyRequestObject myRequestObject = receiveData(socketChannel);logger.log(Level.INFO, myRequestObject.toString());MyResponseObject myResponseObject = new MyResponseObject("response for " + myRequestObject.getName(), "response for " + myRequestObject.getValue());sendData(socketChannel, myResponseObject);logger.log(Level.INFO, myResponseObject.toString());} finally {try {socketChannel.close();} catch(Exception ex) {}}}private static MyRequestObject receiveData(SocketChannel socketChannel) throws IOException {MyRequestObject myRequestObject = null;ByteArrayOutputStream baos = new ByteArrayOutputStream();ByteBuffer buffer = ByteBuffer.allocate(1024);try {byte[] bytes;int size = 0;while ((size = socketChannel.read(buffer)) >= 0) {buffer.flip();bytes = new byte[size];buffer.get(bytes);baos.write(bytes);buffer.clear();}bytes = baos.toByteArray();Object obj = SerializableUtil.toObject(bytes);myRequestObject = (MyRequestObject)obj;} finally {try {baos.close();} catch(Exception ex) {}}return myRequestObject;}private static void sendData(SocketChannel socketChannel, MyResponseObject myResponseObject) throws IOException {byte[] bytes = SerializableUtil.toBytes(myResponseObject);ByteBuffer buffer = ByteBuffer.wrap(bytes);socketChannel.write(buffer);}}
下面是Client的代码，代码比较简单就是启动了100个线程来访问Server
package com.googlecode.garbagecan.test.socket.nio;import java.io.ByteArrayOutputStream;import java.io.IOException;import java.net.InetSocketAddress;import java.net.SocketAddress;import java.nio.ByteBuffer;import java.nio.channels.SocketChannel;import java.util.logging.Level;import java.util.logging.Logger;import com.googlecode.garbagecan.test.socket.SerializableUtil;public class MyClient3 {private final static Logger logger = Logger.getLogger(MyClient3.class.getName());public static void main(String[] args) throws Exception {for (int i = 0; i < 100; i++) {final int idx = i;new Thread(new MyRunnable(idx)).start();}}private static final class MyRunnable implements Runnable {private final int idx;private MyRunnable(int idx) {this.idx = idx;}public void run() {SocketChannel socketChannel = null;try {socketChannel = SocketChannel.open();SocketAddress socketAddress = new InetSocketAddress("localhost", 10000);socketChannel.connect(socketAddress);MyRequestObject myRequestObject = new MyRequestObject("request_" + idx, "request_" + idx);logger.log(Level.INFO, myRequestObject.toString());sendData(socketChannel, myRequestObject);MyResponseObject myResponseObject = receiveData(socketChannel);logger.log(Level.INFO, myResponseObject.toString());} catch (Exception ex) {logger.log(Level.SEVERE, null, ex);} finally {try {socketChannel.close();} catch(Exception ex) {}}}private void sendData(SocketChannel socketChannel, MyRequestObject myRequestObject) throws IOException {byte[] bytes = SerializableUtil.toBytes(myRequestObject);ByteBuffer buffer = ByteBuffer.wrap(bytes);socketChannel.write(buffer);socketChannel.socket().shutdownOutput();}private MyResponseObject receiveData(SocketChannel socketChannel) throws IOException {MyResponseObject myResponseObject = null;ByteArrayOutputStream baos = new ByteArrayOutputStream();try {ByteBuffer buffer = ByteBuffer.allocateDirect(1024);byte[] bytes;int count = 0;while ((count = socketChannel.read(buffer)) >= 0) {buffer.flip();bytes = new byte[count];buffer.get(bytes);baos.write(bytes);buffer.clear();}bytes = baos.toByteArray();Object obj = SerializableUtil.toObject(bytes);myResponseObject = (MyResponseObject) obj;socketChannel.socket().shutdownInput();} finally {try {baos.close();} catch(Exception ex) {}}return myResponseObject;}}}
最后测试上面的代码，首先运行Server类，然后运行Client类，就可以分别在Server端和Client端控制台看到发送或接收到的MyRequestObject或MyResponseObject对象了。关于NIO和IO的比较，下面的两篇文章对理解很有帮助，可以参考一下。
http://tutorials.jenkov.com/java-nio/nio-vs-io.html
https://blogs.oracle.com/slc/entry/javanio_vs_javaio
当我要取的时候，你淘气的躲开了，
