java之eclipse连接数据库实现jsp页面增删改,显示功能

实体类 Users

package com.qf.entity;

public class Users {
   
   
	private int id;//ID
	private String username;//账号
	private String pwd;//密码
	private String name;//户主
	private int age;//年龄
	private String sex;//性别
	public Users() {
   
   
		super();
		// TODO Auto-generated constructor stub
	}
	public Users(int id, String username, String pwd, String name, int age, String sex) {
   
   
		super();
		this.id = id;
		this.username = username;
		this.pwd = pwd;
		this.name = name;
		this.age = age;
		this.sex = sex;
	}
	public int getId() {
   
   
		return id;
	}
	public void setId(int id) {
   
   
		this.id = id;
	}
	public String getUsername() {
   
   
		return username;
	}
	public void setUsername(String username) {
   
   
		this.username = username;
	}
	public String getPwd() {
   
   
		return pwd;
	}
	public void setPwd(String pwd) {
   
   
		this.pwd = pwd;
	}
	public String getName() {
   
   
		return name;
	}
	public void setName(String name) {
   
   
		this.name = name;
	}
	public int getAge() {
   
   
		return age;
	}
	public void setAge(int age) {
   
   
		this.age = age;
	}
	public String getSex() {
   
   
		return sex;
	}
	public void setSex(String sex) {
   
   
		this.sex = sex;
	}
	@Override
	public String toString() {
   
   
		return "Users [id=" + id + ", username=" + username + ", pwd=" + pwd + ", name=" + name + ", age=" + age
				+ ", sex=" + sex + "]";
	}
	
}

工具类 DBManager

package com.qf.util;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

public class DBManager {
   
   
	public static Connection getConnection() throws ClassNotFoundException, SQLException {
   
   
		// 1.加载驱动
		Class.forName("com.mysql.jdbc.Driver");
		// 2. 获得连接, 三个参数分别为：url，用户名，密码
		return DriverManager
				.getConnection("jdbc:mysql://localhost:3306/j1904?useUnicode=true&characterEncoding=utf-8", 
				"root", "root");
	}
	
	// 先打开，后关闭
	public static void closeAll(Connection connection, PreparedStatement statement) {
   
   
		try {
   
   
			if(statement != null) {
   
   
				statement.close();
			}
		} catch (SQLException e) {
   
   
			e.printStackTrace();
		}finally {
   
   
			try {
   
   
				if(connection != null) {
   
   
					connection.close();
				}
			} catch (SQLException e) {
   
   
				e.printStackTrace();
			}
		}
	}
	
	// 先打开，后关闭
	public static void closeAll(Connection connection, PreparedStatement statement, ResultSet resultSet) {
   
   
		try {
   
   
			if(resultSet != null) {
   
   
				resultSet.close()</