使用Java NIO提高服务端程序的性能

            1 // ==================== Program Discription =====================
2 // 程序名称：示例12-14 : SocketChannelDemo.java
3 // 程序目的：学习Java NIO#SocketChannel
4 // ==============================================================
5 
6 
7 import java.nio.ByteBuffer;
8 import java.nio.channels.ServerSocketChannel;
9 import java.nio.channels.SocketChannel;
10 import java.nio.channels.Selector;
11 import java.nio.channels.SelectionKey;
12 import java.nio.channels.SelectableChannel;
13 
14 import java.net.Socket;
15 import java.net.ServerSocket;
16 import java.net.InetSocketAddress;
17 import java.util.Iterator;
18
19 public class SocketChannelDemo
 
20 
21 {
22  public static int PORT_NUMBER = 23;//监听端口
23  ServerSocketChannel serverChannel;
24  ServerSocket serverSocket ;
25  Selector selector ;
26  private ByteBuffer buffer = ByteBuffer.allocateDirect (1024);
27 
28  public static void main (String [] args)
29   throws Exception
30  {
31   SocketChannelDemo server=new SocketChannelDemo();
32   server.init(args);
33   server.startWork();
34  }
35 
36 
37  public void init (String [] argv)throws Exception
38  {
39   int port = PORT_NUMBER;
40 
41   if (argv.length > 0) { 
42    port = Integer.parseInt (argv [0]);
43   }
44 
45   System.out.println ("Listening on port " + port);
46 
47   // 分配一个ServerSocketChannel
48   serverChannel = ServerSocketChannel.open();
49   // 从ServerSocketChannel里获得一个对应的Socket
50   serverSocket = serverChannel.socket();
51   // 生成一个Selector
52   selector = Selector.open();
53 
54   // 把Socket绑定到端口上
55   serverSocket.bind (new InetSocketAddress (port));
56   //serverChannel为非bolck
57   serverChannel.configureBlocking (false);
58 
59   // 通过Selector注册ServerSocetChannel
60   serverChannel.register (selector, SelectionKey.OP_ACCEPT); 
61   
62  }
63 
64     public void startWork()throws Exception
 
65 
66     {
67      while (true) {
68    
69    int n = selector.select();//获得IO准备就绪的channel数量
70 
71    if (n == 0) {
72     continue; // 没有channel准备就绪，继续执行
73    }
74 
75    // 用一个iterator返回Selector的selectedkeys
76    Iterator it = selector.selectedKeys().iterator();
77 
78    // 处理每一个SelectionKey
79    while (it.hasNext()) {
80     SelectionKey key = (SelectionKey) it.next();
81
82     // 判断是否有新的连接到达
83 if (key.isAcceptable()) {
84　　　　　　　　　　　//返回SelectionKey的ServerSocketChannel
85      ServerSocketChannel server =
(ServerSocketChannel) key.channel();
86      SocketChannel channel = server.accept();
87 
88      registerChannel (selector, channel,
89       SelectionKey.OP_READ);
90 
91      doWork (channel);
92     }
93 
94     // 判断是否有数据在此channel里需要读取
95     if (key.isReadable()) {
96        
97      processData (key);
98 
99     }
100 
101     //删除 selectedkeys
102     it.remove();
103    }
104   }
105  }
106  protected void registerChannel (Selector selector,
107   SelectableChannel channel, int ops)
108   throws Exception
109  {
 
110   if (channel == null) {
111    return;  
112   }
113 
114  
115   channel.configureBlocking (false);
116 
117   channel.register (selector, ops);
118  }
119 
120     //处理接收的数据
121  protected void processData (SelectionKey key)
122   throws Exception
123  {
124   
125  
126   SocketChannel socketChannel = (SocketChannel) key.channel();
127   int count;
128 
129   buffer.clear();   // 清空buffer
130 
131   // 读取所有的数据
132   while ((count = socketChannel.read (buffer)) > 0) {
133    buffer.flip();  
134
135    // send the data, don't assume it goes all at once
136    while (buffer.hasRemaining())
137    {
138     //如果收到回车键，则在返回的字符前增加[echo]$字样
139     if(buffer.get()==(char)13)
140     {
141      buffer.clear();
142      buffer.put("[echo]$".getBytes());
143      buffer.flip();
144      
145     }
146     socketChannel.write (buffer);//在Socket里写数据
147    }
148   
149    buffer.clear();  // 清空buffer
150   }
151 
152   if (count < 0) {
153    // count<0，说明已经读取完毕
154    socketChannel.close();
 
155   }
156  }
157 
158 
159  private void doWork (SocketChannel channel)throws Exception
160  {
161   buffer.clear();
162   buffer.put ("
Hello,I am working,please input some thing,and i will echo to you!
[echo] 
$".getBytes());
163   buffer.flip();
164   channel.write (buffer);
165  }
166 
167 }