javaweb中实现增删改查的功能的代码

JavaWeb中实现增删改查功能的代码需要依赖于数据库，下面给出一个简单的示例，包含一个学生信息的实体类`Student`和一个学生信息的DAO类`StudentDAO`，用于操作数据库。这里以MySQL为例，使用JDBC连接数据库。

**1. Student类**

public class Student {
    private int id;
    private String name;
    private int age;
    private String gender;
    private String major;

    public Student(int id, String name, int age, String gender, String major) {
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
        this.major = major;
    }

    //getter and setter methods
}

**2. StudentDAO类**

import java.sql.*;
import java.util.ArrayList;
import java.util.List;

public class StudentDAO {
    private Connection conn;

    public StudentDAO() {
        String url = "jdbc:mysql://localhost:3306/test?useSSL=false&allowPublicKeyRetrieval=true&serverTimezone=UTC";
        String user = "root";
        String password = "password";
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection(url, user, password);
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    //添加学生信息
    public boolean addStudent(Student student) {
        String sql = "insert into student(name, age, gender, major) values(?,?,?,?)";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, student.getName());
            ps.setInt(2, student.getAge());
            ps.setString(3, student.getGender());
            ps.setString(4, student.getMajor());
            int result = ps.executeUpdate();
            if(result > 0) {
                return true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    //删除学生信息
    public boolean deleteStudent(int id) {
        String sql = "delete from student where id=?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setInt(1, id);
            int result = ps.executeUpdate();
            if(result > 0) {
                return true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    //修改学生信息
    public boolean updateStudent(Student student) {
        String sql = "update student set name=?, age=?, gender=?, major=? where id=?";
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ps.setString(1, student.getName());
            ps.setInt(2, student.getAge());
            ps.setString(3, student.getGender());
            ps.setString(4, student.getMajor());
            ps.setInt(5, student.getId());
            int result = ps.executeUpdate();
            if(result > 0) {
                return true;
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
        return false;
    }

    //查询所有学生信息
    public List<Student> getAllStudents() {
        String sql = "select * from student";
        List<Student> list = new ArrayList<>();
        try {
            PreparedStatement ps = conn.prepareStatement(sql);
            ResultSet rs = ps.executeQuery();
            while(rs.next()) {
                int id = rs.getInt("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                String gender = rs.getString("gender");
                String major = rs.getString("