java经典代码实例

import java.io.*; import java.net.*; import java.util.*; /** * This class uses the Server class to provide a multi-threaded server * framework for a relatively simple proxy service. The main() method * starts up the server. The nested Proxy class implements the * Server.Service interface and provides the proxy service. **/ public class ProxyServer { /** * Create a Server object, and add Proxy service objects to it to provide * proxy service as specified by the command-line arguments. **/ public static void main(String[] args) { try { // Check number of args. Must be a multiple of 3 and > 0. if ((args.length == 0) || (args.length % 3 != 0)) throw new IllegalArgumentException("Wrong number of args"); // Create the Server object Server s = new Server(null, 12); // log stream, max connections // Loop through the arguments parsing (host, remoteport, localport) // tuples. For each, create a Proxy, and add it to the server. int i = 0; while(i < args.length) { String host = args[i++]; int remoteport = Integer.parseInt(args[i++]); int localport = Integer.parseInt(args[i++]); s.addService(new Proxy(host, remoteport), localport); } } catch (Exception e) { // Print an error message if anything goes wrong System.err.println(e); System.err.println("Usage: java ProxyServer " + "<host> <remoteport> <localport> ..."); System.exit(1); } } /** * This is the class that implements the proxy service. The serve() method * will be called when the client has connected. At that point, it must * establish a connection to the server, and then transfer bytes back and * forth between client and server. For symmetry, this class implements * two very similar threads as anonymous classes. One thread copies bytes * from client to server, and the other copies them from server to client. * The thread that invoke the serve() method creates and starts these * threads, then just sits and waits for them to exit. **/ public static class Proxy implements Server.Service { String host; int port; /** Remember the host and port we are a proxy for */ public Proxy(String host, int port) { this.host = host; this.port = port; } /** The server invokes this method when a client connects. */ public void serve(InputStream in, OutputStream out) { // These are some sockets we'll use. They are final so they can // be used by the anonymous classes defined below. final InputStream from_client = in; final OutputStream to_client = out; final InputStream from_server; final OutputStream to_server; // Try to establish a connection to the specified server and port // and get sockets to talk to it. Tell our client if we fail. final Socket server; try { server = new Socket(host, port); from_server = server.getInputStream(); to_server = server.getOutputStream(); } catch (Exception e) { PrintWriter pw = new PrintWriter(new OutputStreamWriter(out)); pw.print("Proxy server could not connect to " + host + ":" + port + "\n"); pw.flush(); pw.close(); try { in.close(); } catch (IOException ex) {} return; } // Create an array to hold two Threads. It is declared final so // that it can be used by the anonymous classes below. We use an // array instead of two variables because given the structure of // this program two variables would not work if declared final. final Thread[] threads = new Thread[2]; // Define and create a thread to copy bytes from client to server Thread c2s = new Thread() { public void run() { // Copy bytes 'till EOF from client byte[] buffer = new byte[2048]; int bytes_read; try { while((bytes_read=from_client.read(buffer))!=-1) { to_server.write(buffer, 0, bytes_read); to_server.flush(); } } catch (IOException e) {} finally { // When the thread is done try { server.close(); // close the server socket to_client.close(); // and the client streams from_client.close(); } catch (IOException e) {} } } }; // Define and create a thread to copy bytes from server to client. // This thread works just like the one above. Thread s2c = new Thread() { public void run() { byte[] buffer = new byte[2048]; int bytes_read; try { while((bytes_read=from_server.read(buffer))!=-1) { to_client.write(buffer, 0, bytes_read); to_client.flush(); } } catch (IOException e) {} finally { try { server.close(); // close down to_client.close(); from_client.close(); } catch (IOException e) {} } } }; // Store the threads into the final threads[] array, so that the // anonymous classes can refer to each other. threads[0] = c2s; threads[1] = s2c; // start the threads c2s.start(); s2c.start(); // Wait for them to exit try { c2s.join(); s2c.join(); } catch (InterruptedException e) {} } } } /** * This class is a generic framework for a flexible, multi-threaded server. * It listens on any number of specified ports, and, when it receives a * connection on a port, passes input and output streams to a specified Service * object which provides the actual service. It can limit the number of * concurrent connections, and logs activity to a specified stream. **/ class Server { // This is the state for the server Map services; // Hashtable mapping ports to Listeners Set connections; // The set of current connections int maxConnections; // The concurrent connection limit ThreadGroup threadGroup; // The threadgroup for all our threads PrintWriter logStream; // Where we send our logging output to /** * This is the Server() constructor. It must be passed a stream * to send log output to (may be null), and the limit on the number of * concurrent connections. **/ public Server(OutputStream logStream, int maxConnections) { setLogStream(logStream); log("Starting server"); threadGroup = new ThreadGroup(Server.class.getName()); this.maxConnections = maxConnections; services = new HashMap(); connections = new HashSet(maxConnections); } /** * A public method to set the current logging stream. Pass null * to turn logging off **/ public synchronized void setLogStream(OutputStream out) { if (out != null) logStream = new PrintWriter(out); else logStream = null; } /** Write the specified string to the log */ protected synchronized void log(String s) { if (logStream != null) { logStream.println("[" + new Date() + "] " + s); logStream.flush(); } } /** Write the specified object to the log */ protected void log(Object o) { log(o.toString()); } /** * This method makes the server start providing a new service. * It runs the specified Service object on the specified port. **/ public synchronized void addService(Service service, int port) throws IOException { Integer key = new Int