小编典典

基于此示例，这是一个使用Swing的简单网络客户端/服务器对。请注意与正确同步有关的一些问题：GUI本身是使用事件分配线程构建的invokeLater()。此外，代码还依赖的线程安全性append()。最后，它结合了文章Text Area Scrolling中的一个方便提示。

更新：在Java 7中，append()不再标记为线程安全；invokeLater()用于display()序列更新。

package net;

import java.awt.*;

import java.awt.event.*;

import java.io.*;

import java.net.*;

import java.util.Scanner;

import javax.swing.*;

import javax.swing.text.DefaultCaret;

/**

* A simple network client-server pair

* @http://stackoverflow.com/questions/3245805

*/

public class Echo implements ActionListener, Runnable {

private static final String HOST = "127.0.0.1";

private static final int PORT = 12345;

private final JFrame f = new JFrame();

private final JTextField tf = new JTextField(25);

private final JTextArea ta = new JTextArea(15, 25);

private final JButton send = new JButton("Send");

private volatile PrintWriter out;

private Scanner in;

private Thread thread;

private Kind kind;

public static enum Kind {

Client(100, "Trying"), Server(500, "Awaiting");

private int offset;

private String activity;

private Kind(int offset, String activity) {

this.offset = offset;

this.activity = activity;

}

}

public Echo(Kind kind) {

this.kind = kind;

f.setTitle("Echo " + kind);

f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

f.getRootPane().setDefaultButton(send);

f.add(tf, BorderLayout.NORTH);

f.add(new JScrollPane(ta), BorderLayout.CENTER);

f.add(send, BorderLayout.SOUTH);

f.setLocation(kind.offset, 300);

f.pack();

send.addActionListener(this);

ta.setLineWrap(true);

ta.setWrapStyleWord(true);

DefaultCaret caret = (DefaultCaret) ta.getCaret();

caret.setUpdatePolicy(DefaultCaret.ALWAYS_UPDATE);

display(kind.activity + HOST + " on port " + PORT);

thread = new Thread(this, kind.toString());

}

public void start() {

f.setVisible(true);

thread.start();

}

//@Override

public void actionPerformed(ActionEvent ae) {

String s = tf.getText();

if (out != null) {

out.println(s);

}

display(s);

tf.setText("");

}

//@Override

public void run() {

try {

Socket socket;

if (kind == Kind.Client) {

socket = new Socket(HOST, PORT);

} else {

ServerSocket ss = new ServerSocket(PORT);

socket = ss.accept();

}

in = new Scanner(socket.getInputStream());

out = new PrintWriter(socket.getOutputStream(), true);

display("Connected");

while (true) {

display(in.nextLine());

}

} catch (Exception e) {

display(e.getMessage());

e.printStackTrace(System.err);

}

}

private void display(final String s) {

EventQueue.invokeLater(new Runnable() {

//@Override

public void run() {

ta.append(s + "\u23CE\n");

}

});

}

public static void main(String[] args) {

EventQueue.invokeLater(new Runnable() {

//@Override

public void run() {

new Echo(Kind.Server).start();

new Echo(Kind.Client).start();

}

});

}

}

2020-02-26