Java Socket实战之六 使用NIO包实现Socket通信

本文地址：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; } @Override public 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; } @Override public 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 requests selector = Selector.open(); // Create a new server socket and set to non blocking mode serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(false); // Bind the server socket to the local host and port serverSocketChannel.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 keys Iterator<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/O execute((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