javaweb基础第八课：整合数据库的登录

这节课我们在上节课的基础上整合一下数据库。

既然要整合数据库，首先得有一个数据库，我们就起名叫javaweb_teach，字符编码设置为utf8

然后建一个user表

然后开始整合，首先要添加包，说下往javaweb项目里添加包的步骤:

在/WEB-INF下建一个文件夹叫lib(必须是这个名)
把需要的jar包拷贝到lib中
如果使用的是idea，还需要在Project Structure里添加依赖(eclipse无视此步骤)

以前我们写过一个JdbcTool，我已经把这个项目打包成jar包了，等会上传大家可以下下来直接用,注意别忘可mysql-connector

然后建个bean包，里面放和数据库对应的实体类

下一步，写Mapper用于处理数据库相关操作

LoginServlet.java:

package com.servlet;



import com.bean.User;

import com.dao.UserMapper;



import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

import java.lang.reflect.InvocationTargetException;

import java.sql.SQLException;

import java.util.HashMap;

import java.util.List;

import java.util.Map;



//这个servlet用来处理登录请求

public class LoginServlet extends HttpServlet {



    private UserMapper userMapper = UserMapper.getInstance();



    @Override

    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        String username = req.getParameter("username");

        String password = req.getParameter("password");



        Map<String,Object> map = new HashMap<>();

        map.put("username",username);

        map.put("password",password);



        try {

            List<User> users = userMapper.selectByExample(map);

            if (users != null && users.size() == 1)

            {

                User user = users.get(0);

                if (user != null)

                {

                    //跳转到登录成功的页面

                    /**

                     * 跳转页面使用request.getRequestDispatcher(要跳转的页面的路径).forward(request,response);

                     */

                    req.getRequestDispatcher("/WEB-INF/login_success.jsp").forward(req,resp);

                }

                else

                {

                    //如果登录失败，我们给点提示信息

                    req.setAttribute("errorMsg","登录失败");   //向request域里设置属性和值

                    req.getRequestDispatcher("/WEB-INF/login.jsp").forward(req,resp);

                }

            }

            else

            {

                //如果登录失败，我们给点提示信息

                req.setAttribute("errorMsg","登录失败");   //向request域里设置属性和值

                req.getRequestDispatcher("/WEB-INF/login.jsp").forward(req,resp);

            }

        } catch (SQLException e) {

            e.printStackTrace();

        } catch (IllegalAccessException e) {

            e.printStackTrace();

        } catch (InstantiationException e) {

            e.printStackTrace();

        } catch (NoSuchMethodException e) {

            e.printStackTrace();

        } catch (NoSuchFieldException e) {

            e.printStackTrace();

        } catch (InvocationTargetException e) {

            e.printStackTrace();

        }

    }

}

DataSource.java:

package com.dao;



import com.tool.Dbc;



import java.sql.Connection;

import java.sql.SQLException;



public class DataSource {



    private static String

        driver = "com.mysql.jdbc.Driver",

        url = "jdbc:mysql://localhost:3306/javaweb_teach",

        username = "root",

        password = "root";



    public static Connection getConnection() throws SQLException, ClassNotFoundException {

        Connection connection = Dbc.getConnection(driver, url, username, password);

        return connection;

    }

}

UserMapper.java

package com.dao;



import com.bean.User;

import com.tool.Mapper;



import java.io.IOException;

import java.sql.Connection;

import java.sql.SQLException;



//注意搞成单例

public class UserMapper extends Mapper<User> {



    private static UserMapper instance = null;



    private UserMapper(Connection connection) {

        super(connection);

    }



    private UserMapper(String dbcPropertiesPath) throws SQLException, IOException, ClassNotFoundException {

        super(dbcPropertiesPath);

    }



    public static UserMapper getInstance() {

        if (instance == null)

        {

            try {

                instance = new UserMapper(DataSource.getConnection());

            } catch (SQLException e) {

                e.printStackTrace();

            } catch (ClassNotFoundException e) {

                e.printStackTrace();

            }

        }

        return instance;

    }

}

User.java:

package com.bean;



public class User {

    private String username;

    private String password;



    public User() {

    }



    public User(String username, String password) {

        this.username = username;

        this.password = password;

    }



    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{" +

                "username='" + username + '\'' +

                ", password='" + password + '\'' +

                '}';

    }

}



<%@ page contentType="text/html;charset=UTF-8" language="java" %>

<html>

<head>

    <title>登录</title>

</head>

<body style="text-align: center">

    <form style="margin-top: 100px;border: 1px solid black;text-align: center" action="/login" method="post">

        <input type="text" name="username" placeholder="用户名"><br><br>

        <input type="password" name="password" placeholder="密码"><br><br>

        <!-- 这里开始涉及jsp的知识了，下节课开始讲，先看看效果 -->

        <scan><%=request.getAttribute("errorMsg")%></scan><br>

        <button type="submit">登录</button>

    </form>

</body>

</html>

javaweb基础第八课：整合数据库的登录

猜你喜欢