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。

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

--socketProject
    |--Client.java
    |--GUI.java
    |--SearchInfo.java
    |--Server.java
    |--ServerThread.java

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：

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)。

参考链接

Java请求一个URL，获取返回的数据_杜岚特的博客-CSDN博客

java.io.datainputstream.readunsignedshort_socket编程报异常java.io.EOFException_窦月汐的博客-CSDN博客