JDBC方式从数据库中查询数据并显示

新博客地址https://www.jianshu.com/u/8e54644eafae

1.创建数据库表myuser

DROP TABLE IF EXISTS `myuser`;
CREATE TABLE `myuser` (
  `user_name` varchar(255) NOT NULL COMMENT '姓名',
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `age` int(11) DEFAULT NULL,
  `password` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8;

2.实体类

package yang.mybatis.domain;

public class User {
　　//实体类的成员变量和数据库表的字段名称和类型一致
    private int id;
    private String user_name;
    private int age;
    private String password;
    
    public User(){}
    public User(String name,int id, int age,String password) {
        super();
        this.id = id;
        this.user_name = name;
        this.age = age;
        this.password = password;
    }
　　//创建每个成员变量的set和get方法
    public int getId() {
        return id;
    }
    public void setId(int id) {
        this.id = id;
    }
    public String getUser_name() {
        return user_name;
    }
    public void setUser_name(String name) {
        this.user_name = name;
    }
    public int getAge() {
        return age;
    }
    public void setAge(int age) {
        this.age = age;
    }
    public void setPassword(String password) {
        this.password = password;
    }

    public String getPassword() {
        return password;
    }
    @Override
    public String toString() {
        return "User [id=" + id + ", name=" + user_name + ", age=" + age + "]";
    }



}

3.1UserDao,连接数据库，查询数据库表中所有的记录

package yang.mybatis.dao;

import yang.mybatis.domain.User;

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

/**
 * Created by yangshijing on 2017/11/10 0010.
 */
public class UserDaoTest {
    public List<User> getAll(){
　　　　
        List<User> Users = new ArrayList<User>();

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            String driverClass = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql:///mydb";
            String user = "root";
            String pass= "1234";

            Class.forName(driverClass);
            connection = DriverManager.getConnection(url, user, pass);

            String sql = "SELECT user_name, id, age, password FROM myuser";
            preparedStatement = connection.prepareStatement(sql);

            resultSet = preparedStatement.executeQuery();
            while(resultSet.next()){
                String user_name = resultSet.getString(1);
                int id = resultSet.getInt(2);
                int age = resultSet.getInt(3);
                String password = resultSet.getString(4);
                User userl= new User(user_name,id,age,password);
                Users.add(userl);
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            try {
                if(resultSet != null){
                    resultSet.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }

            try {
                if(preparedStatement != null){
                    preparedStatement.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }

            try {
                if(connection != null){
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        return Users;
    }
}

3.2根据用户Id删除用户数据

   public void deleteById(int id) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        try {
            String driverClass = "com.mysql.jdbc.Driver";
            String url = "jdbc:mysql:///mydb";
            String user = "root";
            String pass= "1234";

            Class.forName(driverClass);
            connection = DriverManager.getConnection(url, user, pass);

            String sql = "DELETE FROM myuser WHERE id=?";
            preparedStatement = connection.prepareStatement(sql);
            preparedStatement.setInt(1,id);
            int i = preparedStatement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            try {
                if(preparedStatement != null){
                    preparedStatement.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }

            try {
                if(connection != null){
                    connection.close();
                }
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

4.1编写查询Servlet

package yang.mybatis.servlet;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import yang.mybatis.dao.UserDaoImp;
import yang.mybatis.dao.UserDaoTest;
import yang.mybatis.domain.User;

import java.io.IOException;
import java.util.List;

/**
 * Created by yangshijing on 2017/11/10 0010.
 */
@Controller
public class ListAllStudent extends javax.servlet.http.HttpServlet {
    @Override
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        doGet(request,response);
    }

    @Override
    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        try {
            UserDaoTest userDaoTest = new UserDaoTest();
            List<User> list = userDaoTest.getAll();
//将从数据库中查询到的数据方法request域中
            request.setAttribute("list",list);
//利用请求转发的方式，将这次请求域中的数据传到另一个页面进行显示    
       　　　　request.getRequestDispatcher("/jsp/hello1.jsp").forward(request,response);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

4.2删除Servlet

package yang.mybatis.servlet;

import yang.mybatis.dao.UserDaoTest;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

/**
 * Created by yangshijing on 2017/11/10 0010.
 */
public class DeleteServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
　　　　　//从request域中获取的数据是String类型
        String id = request.getParameter("id");
        UserDaoTest userDaoTest = new UserDaoTest();
　　　　　//通过Interger.parseInt()方法，将String类型转换为int类型
        userDaoTest.deleteById(Integer.parseInt(id));
        request.getRequestDispatcher("/listAllStudent").forward(request,response);
    }
}

5.Web应用根目录下/jsp/hello1.jsp页面对数据进行显示

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<html>
<head>
    <title>用户列表</title>
</head>
<body>
    <a href="/myAction/listAllStudent.action">SpringMvc</a>
    <a href="/listAllStudent">Servlet</a>
    <br>
　　<!--设置表格边框的宽度-->
    <table border="1" cellpadding="10" cellspacing="0">
    <tr>
        <th>编号</th>
        <th>姓名</th>
        <th>年龄</th>
        <th>密码</th>
        <th>删除</th>
    </tr>
        <c:forEach items="${list}" var="user">
        <tr>
            <td> ${user.id}</td>
            <td> ${user.user_name}</td>
            <td> ${user.age}</td>
            <td> ${user.password}</td>
            <td><a href="/deleteServlet?id=${user.id}">Delete</a></td>
        </tr>
        </c:forEach>
    </table>

</body>
</html>

6.结果