用java链接MySQL插入变量时，网页报500错误

Question

写web时用java链接MySQL插入数据服务器报500错误
java.sql.SQLIntegrityConstraintViolationException: Duplicate entry 'null' for key 'student.PRIMARY'

java代码

import java.sql.*;
import java.util.Objects;

public class database {
    public void insert(String username, String password1, String password2) throws SQLException{
        Connection conn= DriverManager.getConnection("jdbc:mysql://localhost:3306/database","root","Hwg2539785237");
        try{
            Class.forName("com.mysql.cj.jdbc.Driver");
            System.out.println("驱动添加成功，可以进行数据库连接了");
        }catch (Exception e){
            System.out.println("驱动加载失败,错误原因是："+e.getMessage());
        }

        String node="insert into student(id,name,age)values('"+username+"','"+password1+"','"+password2+"')";
        //String insert1="insert into student values('hahaha','wotama','jianzhitiancai')";执行注释代码插入常量时可以正确插入
        Statement stmt = conn.createStatement();
        int result=stmt.executeUpdate(node);
        //int result1=stmt.executeUpdate(insert1);
        System.out.println(result);
    }
}

传给java值的servlet

import java.io.IOException;
import java.sql.SQLException;
import java.util.Objects;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/servlet")
public class servlet extends HttpServlet{
    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        request.setCharacterEncoding("utf-8");
        String name = request.getParameter("username");
        String password1 =request.getParameter("password1");
        String password2 =request.getParameter("password2");

        database data=new database();
        try {
            data.insert(name,password1,password2);//调试时这里是有正确参数的
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request, response);
    }
}

报错截图

看到报错里Duplicate entry 'null'感觉是参数没传过来，但是调试的时候显示在database里的username变量是有输入的数据的，不知道是不是语法错误≧ ﹏ ≦

配置：tomcat，MySQL，mysql-connector-java-8.0.28.jar。编译器：idea2023

Answer 1

个人理解：
感觉是name类型的问题，student.primary应该是student表的主键，传入的name的类型与student表设置的id类型不一致。
也有可能是你写错了，id为啥要与username对应，name为啥要与password1对应，age为啥跟password2对应。。。。。。如果没错的话，你这命名方式。。。说实话，有点离谱。