java在线聊天项目1.0版 异常处理——开启多个客户端，关闭一个客户端后，在其他客户端中再发出信息会出现异常的处理

Posted 2020-10-16 Advancing Swift

异常一

只开启一个客户端，输入信息后关闭，客户端出现如下异常

根据异常说明 ChatClientFrame客户端117行

提示原因是Socket关闭

分析原因

客户端代码

while (connected) {
String str = dis.readUTF();

当窗口关闭后，Socket已经关闭，读的操作还在继续

处理这个异常，代码如下

catch (SocketException e) {
System.out.println("a client has been closed!");
}

同时，

服务端出现下边异常

解决异常

catch(EOFException e) {
System.out.println("a client has been closed,can\'t read message from it.");
}

  

---

 异常二

开启多个客户端，关闭一个客户端后，在其他客户端中再发出信息，服务器端会出现异常

这个问题是由

for(int i=0;i<clients.size();i++) {
Client c=clients.get(i);
c.send(str);
}

此处产生逻辑bug，当一个客户端被关闭之后，这个客户端还在clients集合当中，这个被关闭的客户端还要再执行send(str)发送信息

造成

private void send(String str) {
try {
dos.writeUTF(str);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
};
}

产生异常

---

 解决异常，在集合中把这个客户端删除掉

catch(SocketException e) {
clients.remove(this);
}

---

 

服务器端完整代码如下：

package com.swift;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.EOFException;
import java.io.IOException;
import java.net.BindException;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketException;
import java.util.ArrayList;
import java.util.List;

public class ChatServer {
    
    boolean started = false;
    ServerSocket ss = null;
    Socket s = null;
    List<Client> clients=new ArrayList<Client>();  
    
    public static void main(String[] args) {
        new ChatServer().fun();
    }

    private void fun() {
        try {
            ss = new ServerSocket(8888);
            started = true;
        } catch (BindException e) {
            System.out.println("端口使用中......");
        } catch (IOException e1) {
            e1.printStackTrace();
        }
        try {
            while (started) {
                s = ss.accept();
                System.out.println("a client connected success");
                Client c = new Client(s);
                new Thread(c).start();
                clients.add(c);
            }
        } catch (EOFException e) {
            System.out.println("client has closed.");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                ss.close();
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
    }

    class Client implements Runnable {

        private Socket s;
        private DataInputStream dis;
        private DataOutputStream dos;
        private boolean connected = false;

        public Client(Socket s) {
            this.s = s;
            try {
                this.dis = new DataInputStream(s.getInputStream());
                this.dos = new DataOutputStream(s.getOutputStream());
                connected = true;
            } catch (IOException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        private void send(String str) {
            try {
                dos.writeUTF(str);
            } catch(SocketException e) {
                clients.remove(this);
            } catch (IOException e) {
                e.printStackTrace();
            };
        }
        @Override
        public void run() {
            try {//注意:要包括while循环，如果try在while循环里，则出现socket closed异常
                while (connected) {
                    String str = dis.readUTF();
                    System.out.println(str);
                    for(int i=0;i<clients.size();i++) {
                        Client c=clients.get(i);
                        c.send(str);
                    }
                    
//                     for(Iterator<Client> it=clients.iterator();it.hasNext();) {
//                         Client c=it.next();//方法二，不可取，有同步锁
//                         c.send(str);
//                     }
                    
//                    Iterator<Client> it=clients.iterator();
//                    while(it.hasNext()) {
//                        Client c=it.next();//方法三，不可取，有同步锁,修改需要加锁（此时没修改）
//                        c.send(str);
//                    }
                     
                }
            } catch(EOFException e) {
                System.out.println("a client has been closed,can\'t read message from it.");
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (dis != null) {
                    try {
                        dis.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if(dos!=null) {
                    try {
                        dos.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
                if (s != null) {
                    try {
                        s.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }

        }

    }
}

客户端完整代码如下：

package com.swift;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;
import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.net.ConnectException;
import java.net.Socket;
import java.net.SocketException;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JLabel;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;

public class ChatClientFrame extends JFrame {

    private static final long serialVersionUID = -118470059355655240L;
    Socket s;
    DataOutputStream dos;
    DataInputStream dis;
    private boolean connected = false;
    JLabel label_shang = new JLabel();
    JLabel label_xia = new JLabel();
    JTextField tf = new JTextField(38);
    JTextArea ta = new JTextArea(15, 50);
    JButton button = new JButton();

    public ChatClientFrame() {
        setBounds(200, 200, 500, 400);
        setTitle("客户端聊天工具 —— 1.0");
        // 对窗口进行大的布局，分为三行一列，在pBasic面板上添加三个面板shang zhong xia
        JPanel pBasic = new JPanel();
        pBasic.setLayout(new BorderLayout());// 不设置默认也是这种布局模式
        setContentPane(pBasic);// 把面板放在窗口上，不记得用this.关键字
        JPanel shang = new JPanel();
        JPanel zhong = new JPanel();
        JPanel xia = new JPanel();
        // 设置JPanel面板的大小
        shang.setSize(470, 25);
        zhong.setSize(470, 180);
        xia.setSize(470, 40);
        pBasic.add(shang, BorderLayout.NORTH);
        pBasic.add(zhong, BorderLayout.CENTER);
        pBasic.add(xia, BorderLayout.SOUTH);
        shang.setBackground(Color.red);
        zhong.setBackground(Color.yellow);
        xia.setBackground(Color.blue);

        label_shang.setText("聊天记录");
        shang.add(label_shang);
        ta.setLineWrap(true);// 自动换行
        JScrollPane scroll = new JScrollPane(ta);// 增加滚动条，以便不增加行数
        zhong.add(scroll);
        label_xia.setText("输入信息");
        xia.add(label_xia, BorderLayout.WEST);
        /*
         * 增加功能，窗口监听事件，窗口打开时设置光标焦点在tf文本域中
         */
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowOpened(WindowEvent e) {
                tf.requestFocus();
            }
        });
        xia.add(tf, BorderLayout.CENTER);
        button.setText("发送");
        xia.add(button, BorderLayout.EAST);

        button.addActionListener(new ShareListener());
        tf.addActionListener(new ShareListener());
        pack();
        this.addWindowListener(new WindowAdapter() {
            @Override
            public void windowClosing(WindowEvent e) {
                disconnect();
                System.exit(0);
            }
        });
        setVisible(true);
        // 创建窗体直接调用连接服务器
        connect();
        Thread t=new Thread(new ReceiveThread());
        t.start();
    }

    class ShareListener implements ActionListener {

        @Override
        public void actionPerformed(ActionEvent e) {
            String tfText1 = tf.getText();
            tf.setText("");
            // 当回车或发送按钮时，tfText发送到服务器
            try {
                dos.writeUTF(tfText1);
                dos.flush();
            } catch (IOException e1) {
                e1.printStackTrace();
            }

        }
    }

    class ReceiveThread implements Runnable {

        @Override
        public void run() {
            try {
                while (connected) {
                    String str = dis.readUTF();
                    System.out.println(str);
                    ta.setText(ta.getText()+str+"\\r\\n");
                }
            } catch (SocketException e) {
                System.out.println("a client has been closed!");
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

    public void connect() {
        try {
            s = new Socket("127.0.0.1", 8888);
            System.out.println("connected!");
            connected=true;
            dos = new DataOutputStream(s.getOutputStream());
            dis = new DataInputStream(s.getInputStream());

        } catch (ConnectException e) {
            System.out.println("服务端异常.........");
            System.out.println("请确认服务端是否开启.........");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void disconnect() {
        try {
            if (dos != null)
                dos.close();
            if(dis !=null)
                dis.close();
            if (s != null)
                s.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public static void main(String[] args) {
        new ChatClientFrame();
    }

}