Java套接字实现应用程序对数据库的访问

布满荆棘的人生 2024-05-23 22:01 33阅读 0赞

最近在完成软件体系结构上机实验时，遇到一个有点点小难度的选做题，题目信息如下：

利用套接字技术实现应用程序中对数据库的访问。应用程序只是利用套接字连接向服务器发送一个查询的条件，而服务器负责对数据库的查询，然后服务器再将查询的结果利用建立的套接字返回给客户端，如下图所示。

![84b2e7b9adacea745038a1b9b8a20119.png][]

本来吧，选做题，不太想做的，但是考虑到以后工作的方向和后端相关，那还是做吧。

本次实验需要做一个GUI界面和一个连接查询功能，在论坛上借鉴了其他大佬获取网站内容的部分代码，然后自己做了一个及其简陋的swing界面，算是把这个实验完成了。

本次实验项目结构如下

`Client.java`

客户端使用 `dis.readUTF()` 时，要注意再发送个字符或者空字符，这里发送 `end` ，表示关闭连接。不然会出现 `EOFException` 。

package socketProject;
    
    import java.io.*;
    import java.net.*;
    
    public class Client {
        String studentNum = null;
        String result = null;
    
        public void setStudentNum(String num) {
            this.studentNum = num;
            System.out.println("stu: " + studentNum);
        }
    
        public void run() throws IOException {
            Socket ss = new Socket("127.0.0.1", 8888);
            System.out.println("Socket: " + ss);
            try {
                DataInputStream dis = new DataInputStream(ss.getInputStream());
                DataOutputStream dos = new DataOutputStream(ss.getOutputStream());
                // the interaction
                dos.writeUTF(studentNum); // 向服务器发送学号
                dos.flush();
                result = dis.readUTF().toString(); // 获得客户端的json字符串
                System.out.println(result);
                dos.writeUTF("end"); // 不加这句会报错
                dos.flush();
                if (dos != null)
                    dos.close();
                if (dis != null)
                    dis.close();
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                if (ss != null)
                    ss.close();
            }
        }
    	// gui界面用于获取json结果
        public String getResult() {
            return result;
        }
    }

`Server.java`

package socketProject;
    
    import java.io.*;
    import java.net.*;
    
    public class Server extends Thread {
        public static final int PORT = 8888;
    
        // public static void main(String[] args) throws IOException {
        public void run() {
            try (ServerSocket serverSocket = new ServerSocket(PORT)) {
                System.out.println("ServerSocket: " + serverSocket);
                try {
                    while (true) {
                        Socket socket = serverSocket.accept();
                        System.out.println("Socket accept: " + socket);
                        Thread thread = new Thread(new ServerThread(socket));
                        thread.start(); // 开启一个线程，使之支持接收多个客户端的请求
                    }
                } finally {
                    serverSocket.close();
                }
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

`ServerThread.java`

package socketProject;
    
    import java.io.*;
    import java.net.*;
    
    public class ServerThread extends Thread {
        Socket socket = null;
    
        public ServerThread(Socket socket) {
            this.socket = socket;
        }
    
        public void run() {
            try {
                DataInputStream dis = new DataInputStream(socket.getInputStream());
                DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
                while (true) {
                    String str = dis.readUTF().toString();
                    String data = new SearchInfo().run(str);
                    if (str.equals("end"))
                        break;
    
                    dos.writeUTF(data);
                }
                dos.close();
                dis.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }

`SearchInfo.java`

package socketProject;
    
    import java.io.*;
    import java.net.*;
    
    public class SearchInfo {
        public String run(String s) {
            String url = "your database interface";
            String param = s;
            String sendGET = GetUrl(url, param);
            return sendGET;
        }
        
        public static String GetUrl(String url, String param) {
            String result = ""; // define the result str
            BufferedReader read = null; // define the access result
            
            try {
                URL realUrl = new URL(url + param);
                URLConnection connection = realUrl.openConnection();
                
                connection.setRequestProperty("accept", "*/*");
                connection.setRequestProperty("connection", "Keep-Alive");
                connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
                // 这里补充通用的请求属性
                connection.connect(); // 建立实际的连接
                
                read = new BufferedReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
                String line;
                while ((line = read.readLine()) != null) {
                    result += line;
                }
            } catch (Exception e) {
                e.printStackTrace();
            } finally {
                if (read != null) {// 关闭流
                    try {
                        read.close();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
            return result;
        }
        
        public String getJSON(String param) {
            return param;
        }
    }

`GUI.java`

package socketProject;
    
    import java.awt.*;
    import java.awt.event.*;
    import java.io.IOException;
    import javax.swing.*;
    
    public class GUI extends JFrame {
        private JButton connectDataBase;
        private JLabel entryStudentNum;
        private JTextField studentNum;
        private JButton sendRequest;
        private JLabel showResponseMsg;
        private JPanel northPanel;
        private JPanel southPanel;
    
        public GUI() {
            init();
        }
    
        public void init() {
            setTitle("没啥技术含量的东西");
            // define the component for the window
            connectDataBase = new JButton("连接数据库");
            entryStudentNum = new JLabel("输入学号");
            studentNum = new JTextField();
            sendRequest = new JButton("发送");
            showResponseMsg = new JLabel();
    
            // add the component to the panel
            this.setLayout(new GridLayout(2, 1));
    
            northPanel = new JPanel(new GridLayout(1, 4));
    
            northPanel.add(connectDataBase);
            northPanel.add(entryStudentNum);
            northPanel.add(studentNum);
            northPanel.add(sendRequest);
    
            southPanel = new JPanel(new GridLayout(1, 1));
    
            southPanel.add(showResponseMsg);
    
            setButtons();
    
            this.add(northPanel);
            this.add(southPanel);
            // initial the window
            setBounds(400, 200, 600, 120);
            setResizable(false);
            setDefaultCloseOperation(EXIT_ON_CLOSE);
            setVisible(true);
        }
    
        public void setButtons() {
            connectDataBase.addActionListener(new ActionListener() {
                @Override
                public void actionPerformed(ActionEvent e) {
                    // 这里初始化服务端
                    Server server1 = new Server();
                    Thread th1 = new Thread(server1);
                    th1.start();
                    // 这里一定要开启服务端线程，否则在点击此按钮后，整个界面会卡住，无法进行下一步操作
                }
            });
    
            sendRequest.addActionListener(new ActionListener() {
    
                @Override
                public void actionPerformed(ActionEvent e) {
                    Client client1 = new Client();
                    client1.setStudentNum(studentNum.getText());
                    // 获取文本框的文字，并赋给客户端的studentNum保存
                    try {
                        client1.run();
                    } catch (IOException e1) {
                        e1.printStackTrace();
                    }
                    showResponseMsg.setText(client1.getResult());
                    // 将得到的数据显示在界面上
                }
            });
        }
    
        public static void main(String[] args) {
            new GUI();
        }
    }

最终效果如下：

![3442799f44eba59f6328614940f611d2.png][]

使用时，先点击连接数据库，然后根据学校提供的接口，输入自己的学号，点击发送，即可查询个人信息。

不过由于项目工作区非maven以及未来方向非Java的缘故，没有去深究如何提取json的值 (偷个懒) 。

[84b2e7b9adacea745038a1b9b8a20119.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/23/82c32320ba324b21baf11c58b853bf2f.png
[3442799f44eba59f6328614940f611d2.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/05/23/a1a2633370f7412eaa30c9fb71b5efbb.png