NIO编写Socket服务器

下面程序接收客户端输入一行文本（以“\r\n”）结束，并向客户端回显输入的文本。如果输入的文本是 “get file:xxxx”模式，则把“xxxx” 解析为服务器class path下的一个文件，如果找到该文件，则回显该文件的内容，如果找不到文件，回显文件不能找到的消息。

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1. import java.io.IOException;  
2. import java.net.InetSocketAddress;  
3. import java.net.URL;  
4. import java.nio.ByteBuffer;  
5. import java.nio.channels.SelectionKey;  
6. import java.nio.channels.Selector;  
7. import java.nio.channels.ServerSocketChannel;  
8. import java.nio.channels.SocketChannel;  
9. import java.nio.charset.Charset;  
10. import java.nio.charset.StandardCharsets;  
11. import java.nio.file.Files;  
12. import java.nio.file.Path;  
13. import java.nio.file.Paths;  
14. import java.util.Iterator;  
15. import java.util.Set;  
16.   
17. public class NIOServer {  
18.     private static final Charset DEFAULT_CHARSET = StandardCharsets.ISO_8859_1;  
19.   
20.     private static final int BUFFER_SIZE = 1024;  
21.   
22.     private int port = 8081;  
23.   
24.     public NIOServer(int port) {  
25.         this.port = port;  
26.     }  
27.   
28.     public NIOServer() {  
29.     }  
30.   
31.     public void start() {  
32.         ServerSocketChannel ssc = null;  
33.         try {  
34.             ssc = ServerSocketChannel.open();  
35.             ssc.configureBlocking(false);  
36.             ssc.bind(new InetSocketAddress(this.port));  
37.             Selector sel = Selector.open();  
38.             ssc.register(sel, SelectionKey.OP_ACCEPT);  
39.             while (true) {  
40.                 Set<SelectionKey> keySet = null;  
41.                 try {  
42.                     sel.select();  
43.                     keySet = sel.selectedKeys();  
44.                 } catch (Exception e) {  
45.                     e.printStackTrace();  
46.                     break;  
47.                 }  
48.   
49.                 for (Iterator<SelectionKey> it = keySet.iterator(); it.hasNext();) {  
50.                     SelectionKey sKey = it.next();  
51.                     it.remove();  
52.                     try {  
53.                         if (sKey.isAcceptable()) {  
54.                             ServerSocketChannel serChannel = (ServerSocketChannel) sKey.channel();  
55.                             SocketChannel clientChannel = serChannel.accept();  
56.                             clientChannel.configureBlocking(false);  
57.   
58.                             SelectionKey k2 = clientChannel.register(sel, SelectionKey.OP_READ);  
59.                             k2.attach(ByteBuffer.allocate(BUFFER_SIZE));  
60.   
61.                         } else if (sKey.isWritable()) {  
62.                             SocketChannel clientChannel = (SocketChannel) sKey.channel();  
63.                             ByteBuffer[] bfs = (ByteBuffer[]) sKey.attachment();  
64.                             if (bfs[bfs.length - 1].hasRemaining()) {  
65.                                 clientChannel.write(bfs);  
66.                             } else {  
67.                                 clientChannel.close();  
68.   
69.                             }  
70.   
71.                         } else if (sKey.isReadable()) {  
72.                             SocketChannel clientChannel = (SocketChannel) sKey.channel();  
73.                             ByteBuffer bf = (ByteBuffer) sKey.attachment();  
74.                             String msg = "";  
75.                             boolean clientEnd = false;  
76.                             if (bf.hasRemaining()) {  
77.                                 int len = clientChannel.read(bf);  
78.                                 if (len != -1 && bf.position() > 1) {  
79.                                     char lastChar = (char) bf.get(bf.position() - 1);  
80.                                     char last2Char = (char) bf.get(bf.position() - 2);  
81.                                     if (String.valueOf(new char[] { last2Char, lastChar }).equals("\r\n")) {  
82.                                         System.out.println("client inupt end.");  
83.                                         clientEnd = true;  
84.                                     }  
85.                                 }  
86.   
87.                                 if (len == -1) {  
88.                                     System.out.println("client closed.");  
89.                                     clientEnd = true;  
90.                                 }  
91.   
92.                             } else {  
93.                                 System.out.println("buff is full.");  
94.                                 msg = "You can only enter " + BUFFER_SIZE + " chars\r\n";  
95.                                 clientEnd = true;  
96.                             }  
97.   
98.                             if (clientEnd) {  
99.                                 ByteBuffer[] att = processInput(bf, msg);  
100.                                 clientChannel.register(sel, SelectionKey.OP_WRITE, att);  
101.                             }  
102.                         }  
103.                     } catch (Exception e) {  
104.                         sKey.cancel();  
105.                         e.printStackTrace();  
106.                     }  
107.                 }  
108.   
109.             }  
110.   
111.         } catch (IOException e) {  
112.             e.printStackTrace();  
113.         } finally {  
114.             if (ssc != null) {  
115.                 try {  
116.                     ssc.close();  
117.                 } catch (IOException e) {  
118.                     e.printStackTrace();  
119.                 }  
120.             }  
121.         }  
122.   
123.     }  
124.   
125.     private ByteBuffer[] processInput(ByteBuffer bf, String msg) throws Exception {  
126.         bf.flip();  
127.         ByteBuffer promptMsg = ByteBuffer.wrap((msg + "You just input:\r\n").getBytes(DEFAULT_CHARSET));  
128.   
129.         String inputMsg = new String(bf.array(), bf.position(), bf.limit(), DEFAULT_CHARSET).trim();  
130.   
131.         ByteBuffer[] att = new ByteBuffer[] { promptMsg, bf };  
132.   
133.         if (inputMsg.indexOf("get file:") >= 0) {  
134.             String fileName = inputMsg.substring("get file:".length()).trim();  
135.             System.out.println("fileName=" + fileName);  
136.             URL fileURL = this.getClass().getClassLoader().getResource(fileName);  
137.             if (fileURL != null) {  
138.                 Path path = Paths.get(fileURL.toURI());  
139.                 System.out.println(path);  
140.   
141.                 ByteBuffer fileData = ByteBuffer.wrap(Files.readAllBytes(path));  
142.                 ByteBuffer info = ByteBuffer  
143.                         .wrap(("The content of file " + fileName + ":\r\n").getBytes(DEFAULT_CHARSET));  
144.                 att = new ByteBuffer[] { promptMsg, bf, info, fileData };  
145.   
146.             } else {  
147.                 String errMsg = "fileName: " + fileName + " not found in the classpath.";  
148.                 System.out.println(errMsg);  
149.   
150.                 att = new ByteBuffer[] { promptMsg, bf, ByteBuffer.wrap(errMsg.getBytes(DEFAULT_CHARSET)) };  
151.   
152.             }  
153.   
154.         }  
155.         return att;  
156.     }  
157.   
158.     public static void main(String[] args) {  
159.         new NIOServer().start();  
160.     }  
161.   
162. }