【个人实习日志】使用Jsp+Servlet实现简单的登陆功能

使用Jsp+Servlet实现简单的登陆功能

开发环境：IDEA2020、Tomcat8.0、Mysql5.7、Jdk1.8
1、新建文件
打开IDEA新建一个Java Web Application项目，选择Tomcat，完成相应配置点击finish

2、在web目录下新建lib文件夹
mysql-connector-java
将下载好的mysql-connector-java放入lib中并导入jar包

3、文件目录

bean 包中主要存放实体类信息；
dao 包中类主要处理与数据库的交互，登录需要用到查询和插入数据库功能；
service 包主要存放一些业务类，在dao层对数据库进行操作时对数据进行一个预处理；
servlet 包主要作为控制层来处理web发送的数据，处理用户的请求信息；
test 文件用于开发过程中测试功能；
util 包主要存放一些工具类如数据库连接；
Web 文件下主要存放需要用到的jsp文件以及一些网页的静态资源；

4、具体代码
（1）util包中的类实现数据库连接功能
DBUtil.java

package com.wut.util;

import java.sql.*;

public class DBUtil {
    public static Connection getConnection() throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");
        Connection connection= DriverManager.getConnection("jdbc:mysql://localhost:3306/wut","root","password");
        return connection;
    }

    public static void close(ResultSet resultSet, PreparedStatement preparedStatement,Connection connection) throws SQLException {
        if(resultSet!=null) {
            resultSet.close();
        }
        if (preparedStatement != null) {
            preparedStatement.close();
        }
        if (connection != null) {
            connection.close();
        }
    }
}

(2)dao包中主要是数据库相关操作的类
Userdao.java

package com.wut.dao;

import com.wut.bean.User;
import com.wut.util.DBUtil;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

public class UserDao {
    public  List<User> findAll() throws ClassNotFoundException, SQLException {
    /*
        1.加载驱动
        2.创建连接
        3.写sql
        4.statement对象
        5.执行sql得到结果集
        6.处理结果集
        7.关闭资源
         */
        List<User> list=new ArrayList<>();
//        Class.forName("com.mysql.jdbc.Driver");
//        Connection connection=DriverManager.getConnection("jdbc:mysql://localhost:3306/wut","root","password");
        Connection connection =DBUtil.getConnection();
        System.out.println("获得连接成功");
        String sql="select * from tb_user";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        ResultSet resultSet=preparedStatement.executeQuery();
        while(resultSet.next()){
            User user=new User();
            int id = resultSet.getInt(1);
            String username = resultSet.getString(2);
            String password = resultSet.getString(3);
            user.setId(id);
            user.setUsername(username);
            user.setPassword(password);
            list.add(user);
        }
       DBUtil.close(resultSet,preparedStatement,connection);
        return list;
    }

    public void deleteById(int id) throws SQLException, ClassNotFoundException {
        Connection connection=DBUtil.getConnection();
        System.out.println("获得连接成功");
        String sql="delete from tb_user where id =?";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setInt(1,id);
        preparedStatement.executeUpdate();
        DBUtil.close(null,preparedStatement,connection);
    }

    public User findByname(String username) throws SQLException, ClassNotFoundException {
        Connection connection=DBUtil.getConnection();
        String sql="select password from tb_user where username=?";
        PreparedStatement preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setString(1,username);
        ResultSet resultSet=preparedStatement.executeQuery();
        User user=new User();
        while(resultSet.next()){
            int id = resultSet.getInt(1);
            String name = resultSet.getString(2);
            String password = resultSet.getString(3);
            user.setId(id);
            user.setUsername(name);
            user.setPassword(password);
        }
        return user;
    }
}

(3)bean包中存放的是项目需要用到的实体类
User.java

package com.wut.bean;

public class User {
    private int id;
    private String username;
    private String password;

    public User(){};

    public User(int id, String username, String password) {
        this.id = id;
        this.username = username;
        this.password = password;
    }

    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 getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String toString() {
        return "User{" +
                "id=" + id +
                ", username='" + username + '\'' +
                ", password='" + password + '\'' +
                '}';
    }
}

(4)service包中的类和dao包中的类共同完成数据处理
UserService.java

package com.wut.service;

import com.wut.bean.User;
import com.wut.dao.UserDao;

import java.sql.SQLException;

public class UserService {
    public Boolean login(String username, String password) {
        UserDao userDao=new UserDao();
        User user=null;
        try {
            user=userDao.findByname(username);
        } catch (SQLException throwables) {
            throwables.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        if(user!=null&&user.getPassword().equals(password)){
            return true;
        }else {
            return false;
        }
    }
}

(5)servlet作为控制层，负责对从jsp页面发送的表单数据进行处理
LoginServlet.java

package com.wut.servlet;

import com.wut.service.UserService;

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

public class LoginServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String username=request.getParameter("username");
        String password=request.getParameter("password");
        UserService userService=new UserService();
        Boolean flag=userService.login(username,password);
            if(flag){
                response.sendRedirect("success.jsp");
            }else {
                response.sendRedirect("index.jsp");
            }
    }
}

(6)web.xml文件负责将一个jsp页面与一个servlet类连接在一起
web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         version="4.0">
    <servlet>
        <servlet-name>Login</servlet-name>
        <servlet-class>com.wut.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
</web-app>

(7)登录页面
index.jsp

<%--
  Created by IntelliJ IDEA.
  User: wuzexue
  Date: 2020/7/20
  Time: 9:05
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
  <head>
    <title>登录</title>
  </head>
  <body>
<form action="login" method="post">
  用户:<input type="text" name="username"><br>
  密码:<input type="password" name="password"><br>
  <input type="submit" value="登录">
</form>
  </body>
</html>

5、运行结果
index.jsp页面

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