第15章 网络编程(11)

extends Thread {
private Socket socket;
private BufferedReader in;
private PrintWriter out;
private static int counter = 0;
private int id = counter++;
private static int threadcount = 0;
public static int threadCount() {
return threadcount;
}
public JabberClientThread(InetAddress addr) {
System.out.println("Making client " + id);
threadcount++;
try {
socket =
new Socket(addr, MultiJabberServer.PORT);
} catch(IOException e) {
// If the creation of the socket fails,
// nothing needs to be cleaned up.
}
try {
in =
new BufferedReader(
new InputStreamReader(
socket.getInputStream()));
// Enable auto-flush:
out =
new PrintWriter(
new BufferedWriter(
new OutputStreamWriter(
socket.getOutputStream())), true);
start();
} catch(IOException e) {
// The socket should be closed on any
// failures other than the socket
// constructor:
try {
socket.close();
} catch(IOException e2) {}
}
// Otherwise the socket will be closed by
// the run() method of the thread.
}
public void run() {
try {
for(int i = 0; i < 25; i++) {
out.println("Client " + id + ": " + i);
String str = in.readLine();
System.out.println(str);
}
out.println("END");
} catch(IOException e) {
} finally {
// Always close it:
try {
socket.close();
} catch(IOException e) {}
threadcount--; // Ending this thread
}
}
}

public class MultiJabberClient {
static final int MAX_THREADS = 40;
public static void main(String[] args)
throws IOException, InterruptedException {
InetAddress addr =
InetAddress.getByName(null);
while(true) {
if(JabberClientThread.threadCount()
< MAX_THREADS)
new JabberClientThread(addr);
Thread.currentThread().sleep(100);
}
}
} ///:~

JabberClientThread构建器获取一个InetAddress，并用它打开一个套接字。大家可能已看出了这样的一个套路：Socket肯定用于创建某种Reader以及／或者Writer（或者InputStream和／或OutputStream）对象，这是运用Socket的唯一方式（当然，我们可考虑编写一、两个类，令其自动完成这些操作，避免大量重复的代码编写工作）。同样地，start()执行线程的初始化，并调用run()。在这里，消息发送给服务器，而来自服务器的信息则在屏幕上回显
出来。然而，线程的“存在时间”是有限的，最终都会结束。注意在套接字创建好以后，但在构建器完成之前，假若构建器失败，套接字会被清除。否则，为套接字调用close()的责任便落到了run()方法的头上。
threadcount跟踪计算目前存在的JabberClientThread对象的数量