如何用Java API监控登录登出时间并存储至MySQL及问题排查

Let's break down the problems in your code and walk through the fixes step by step:

1. Critical Issues in the Client (Test.java) #

Your client code has several blocking problems that prevent it from sending a valid request to the backend:

a. Invalid Return Statement #

The line return new java.sql.Timestamp(today.getTime()); in your main method is invalid—main is a void method and can't return a value. This causes a compilation error, meaning your code never even runs past this point.

b. Unreachable Code #

The username retrieval logic (String username = System.getProperty("user.name");) comes after the invalid return statement, so it's never executed.

c. Incorrect URL Construction #

You're using literal placeholders ({userName}/{systemLoginTime}) in your URL instead of replacing them with actual values. This results in an invalid endpoint that the backend can't process.

d. Mismatched Request Format #

Your client sends a JSON body, but your backend expects path variables for the POST request. These two approaches don't align.

Corrected Client Code

import java.io.*;
import java.net.*;
import java.sql.Timestamp;
import java.util.Date;

public class Test {
    public static void main(String[] args) throws IOException {
        // Get current OS username and formatted login timestamp
        String userName = System.getProperty("user.name");
        Timestamp systemLoginTime = new Timestamp(new Date().getTime());
        String formattedTime = systemLoginTime.toString(); // MySQL-friendly format: yyyy-MM-dd HH:mm:ss

        // Build valid URL with encoded values (handles special characters)
        String urlString = String.format("http://localhost:8080/insert/%s/%s",
                URLEncoder.encode(userName, "UTF-8"),
                URLEncoder.encode(formattedTime, "UTF-8"));
        URL url = new URL(urlString);

        try {
            System.out.println("Username: " + userName);
            System.out.println("Login Time: " + formattedTime);
            System.out.println("Request URL: " + url.toString());

            // Open connection and configure for POST
            URLConnection urlc = url.openConnection();
            urlc.setDoOutput(true);
            urlc.setAllowUserInteraction(false);

            // No body needed (using path variables) - just close the output stream
            PrintStream ps = new PrintStream(urlc.getOutputStream());
            ps.close();

            // Read backend response
            BufferedReader br = new BufferedReader(new InputStreamReader(urlc.getInputStream()));
            String line;
            while ((line = br.readLine()) != null) {
                System.out.println("Backend Response: " + line);
            }
            br.close();
        } catch (Exception e) {
            System.out.println("Error occurred:");
            e.printStackTrace(); // Print full error details for debugging
        }
    }
}

2. Backend Verification Steps #

Even if your client works, ensure your Spring Boot setup is correct:

a. Database Configuration #

Check your application.properties (or application.yml) has valid MySQL credentials:

spring.datasource.url=jdbc:mysql://localhost:3306/your_database_name?useSSL=false&serverTimezone=UTC
spring.datasource.username=your_db_username
spring.datasource.password=your_db_password
spring.datasource.driver-class-name=com.mysql.cj.jdbc.Driver

b. Database Table Schema #

Confirm your mycopinsert table exists with the right columns. Create it if needed:

CREATE TABLE mycopinsert (
    id INT AUTO_INCREMENT PRIMARY KEY,
    userName VARCHAR(50) NOT NULL,
    systemLoginTime DATETIME NOT NULL,
    systemLogoffTime DATETIME NULL
);

c. Enable Debug Logging #

Add this to application.properties to see the exact SQL queries being executed:

logging.level.org.springframework.jdbc.core=DEBUG

This will help you verify if values are being passed correctly to the database.

3. Optional: Improve Backend with Request Body (Best Practice) #

Using path variables for POST requests isn't ideal. A more RESTful approach is to send data in the request body:

Updated Controller #

package com.example.demo;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class MyCopController {
    @Autowired
    MyCopRepo ar;

    @PostMapping("/insert")
    public String myCop(@RequestBody LoginRequest loginRequest) {
        return ar.add(loginRequest.getUserName(), loginRequest.getSystemLoginTime());
    }

    // DTO to hold request data
    static class LoginRequest {
        private String userName;
        private String systemLoginTime;

        // Getters and setters
        public String getUserName() { return userName; }
        public void setUserName(String userName) { this.userName = userName; }
        public String getSystemLoginTime() { return systemLoginTime; }
        public void setSystemLoginTime(String systemLoginTime) { this.systemLoginTime = systemLoginTime; }
    }
}

Updated Client for JSON Body #

Modify your client to send a JSON payload instead of using path variables (adjust the Test.java code accordingly).

Key Fixes Recap #

• Removed the invalid return statement causing compilation errors
• Properly retrieved username and formatted timestamp
• Built a valid URL with encoded values
• Aligned client request format with backend expectations
• Added detailed error logging for easier debugging

内容的提问来源于stack exchange，提问作者S.B.S.Ganesh