Servlet&HTTP&Request8_登录案例

案例：用户登录

1、用户登录案例需求：

　　1.编写login.html登录页面

　　　　username & password 两个输入框　　

　　2.使用Druid数据库连接池技术,操作mysql，day14数据库中user表

　　3.使用JdbcTemplate技术封装JDBC

　　4.登录成功跳转到SuccessServlet展示：登录成功！用户名,欢迎您

　　5.登录失败跳转到FailServlet展示：登录失败，用户名或密码错误

2、分析

3、开发步骤

　1. 创建项目，导入html页面，配置文件，jar包

　　新建一个module，模块名为day08_test

　　把login.html放入web目录下，druid.properties放在src下，web下创建一个WEB-INF目录，把lib目录粘到WEB-INF里，lib右键Add as Library

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/day08_test/loginServlet" method="post">
        用户名:<input type="text" name="username"> <br>
        密码:<input type="password" name="password"><br>

        <input type="submit" value="登录">

    </form>
</body>
</html>

　　druid.property

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql:///day08
username=root
password=root
initialSize=5
maxActive=10
maxWait=3000

　2. 创建数据库环境

CREATE DATABASE day08;

USE day08;

CREATE TABLE USER(
    id INT PRIMARY KEY AUTO_INCREMENT,
    username VARCHAR(32) UNIQUE NOT NULL,
    PASSWORD VARCHAR(32) NOT NULL
);

　　在user表中手动添加几条记录

　3. 创建包cn.itcast.domain,创建类User

package cn.itcast.domain;

/**
 * 用户的实体类
 */
public class User {
    private int id;
    private String username;
    private String 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. 创建包cn.itcast.util,编写工具类JDBCUtils

package cn.itcast.util;

import com.alibaba.druid.pool.DruidDataSourceFactory;

import javax.sql.DataSource;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.Properties;

/**
 * JDBC工具类 使用Druid连接池
 */
public class JDBCUtils {

    private static DataSource ds;

    static {
        try {
            //1. 加载配置文件
            Properties pro = new Properties();
            //使用ClassLoader加载配置i文件，获取字节输入流
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("druid.properties");

            pro.load(is);

            //2. 初始化连接池对象
            ds = DruidDataSourceFactory.createDataSource(pro);

        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        }


    }
    /**
     * 获取连接池对象
     */
    public static DataSource getDataSource(){
        return ds;
    }


    /**
     * 获取连接Connection对象
     */
    public static Connection getConnection() throws SQLException {
        return ds.getConnection();
    }
}

　5. 创建包cn.itcast.dao,创建类UserDao,提供login方法

package cn.itcast.dao;

import cn.itcast.domain.User;
import cn.itcast.util.JDBCUtils;
import org.springframework.dao.DataAccessException;
import org.springframework.jdbc.core.BeanPropertyRowMapper;
import org.springframework.jdbc.core.JdbcTemplate;

/**
 * 操作数据库中User表的类
 */
public class UserDao {

    //声明JDBCTemplate对象公用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    /**
     * 登录方法
     * @param loginUser 只有用户名和密码
     * @return user包含用户全部数据，没有查询到返回null
     */
    public User login(User loginUser){
        try {
            //1. 编写sql
            String sql ="select * from user where username=? and password=?";
            //2. 调用query方法
            User user = template.queryForObject(sql,
                    new BeanPropertyRowMapper<User>(User.class),
                    loginUser.getUsername(),
                    loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {
            e.printStackTrace();//记录日志
            return null;
        }
    }
}

　6. 编写cn.itcast.web.servlet.LoginServlet类

package cn.itcast.web.servlet;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;

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

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 设置编码
        request.setCharacterEncoding("utf-8");
        //2. 获取请求参数
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //3. 封装User对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);

        //4. 调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser);

        //5. 判断user
        if(user == null){
            request.getRequestDispatcher("/failServlet").forward(request,response);

        }else {
            //存储数据
            request.setAttribute("user",user);
            //转发
            request.getRequestDispatcher("/successServlet").forward(request,response);
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

　7. 编写FailServlet和SuccessServlet类

package cn.itcast.web.servlet;

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

@WebServlet("/failServlet")
public class FailServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //给页面写一句话
        //设置编码
        response.setContentType("text/html;charset=utf-8");
        //输出
        response.getWriter().write("登录失败，用户名或密码错误");
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

package cn.itcast.web.servlet;

import cn.itcast.domain.User;

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

@WebServlet("/successServlet")
public class SuccessServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取request域中共享的user对象
        User user = (User) request.getAttribute("user");
        if(user != null){
            //给页面写一句话
            //设置编码
            response.setContentType("text/html;charset=utf-8");
            //输出
            response.getWriter().write("登录成功！"+user.getUsername()+",欢迎您");
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

　8. login.html中form表单的action路径的写法

　　虚拟目录+Servlet的资源路径

　以上完成后可以访问http://localhost:8080/day08_test/login.html，输入错误的用户名和密码，或者是输入正确的用户名密码，提交后就会在浏览器展示信息。

　9. BeanUtils工具类，简化数据封装

　　LoginServlet类可以简化为

package cn.itcast.web.servlet;

import cn.itcast.dao.UserDao;
import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
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.util.Map;

@WebServlet("/loginServlet")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 设置编码
        request.setCharacterEncoding("utf-8");
   
       //2. 获取所有请求参数
        Map<String, String[]> map = request.getParameterMap();
        //3. 创建User对象
        User loginUser = new User();
        //3.2 使用BeanUtils封装
        try {
            BeanUtils.populate(loginUser,map);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        //4. 调用UserDao的login方法
        UserDao dao = new UserDao();
        User user = dao.login(loginUser);

        //5. 判断user
        if(user == null){
            request.getRequestDispatcher("/failServlet").forward(request,response);

        }else {
            //存储数据
            request.setAttribute("user",user);
            //转发
            request.getRequestDispatcher("/successServlet").forward(request,response);
        }
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        this.doPost(request,response);
    }
}

　　用于封装JavaBean的

　　a. JavaBean：标准的Java类

　　　1. 要求：

　　　　　i. 类必须被public修饰

　　　　　ii. 必须提供空参的构造器

　　　　　iii. 成功变量必须使用private修饰

　　　　　iiii. 提供公共setter和getter方法

　　　2. 功能：封装数据

　　b. 概念

　　　成员变量：

　　　属性：setter和getter方法截取后的产物。例如：getUsername() --> Username--> username

　　c. 方法：

　　　　i. setProperty()：操作的是属性，不是成员变量

　　　　ii. getProperty()：操作的是属性，不是成员变量

　　　　iii. popute(Objcet obj,Map map)：将map集合的键值对信息，封装到对应的JavaBean对象中

　　d. 演示：

package cn.itcast.domain;

/**
 * 用户的实体类
 */
public class User {
    private int id;
    private String username;
    private String password;

    private String gender;

    public void setHehe(String gender){
        this.gender = gender;
    }

    public String getHehe(){
       return gender;
    }

    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 + '\'' +
                ", gender='" + gender + '\'' +
                '}';
    }
}

package cn.itcast.test;

import cn.itcast.domain.User;
import org.apache.commons.beanutils.BeanUtils;
import org.junit.Test;

import java.lang.reflect.InvocationTargetException;

public class BeanUtilsTest {

    @Test
    public void test(){
        User user = new User();
        try {
            BeanUtils.setProperty(user,"username","zhangsan");
            BeanUtils.setProperty(user,"hehe","male");
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        }

        System.out.println(user);

        try {
            String gender = BeanUtils.getProperty(user, "hehe");
            System.out.println(gender);
        } catch (IllegalAccessException e) {
            e.printStackTrace();
        } catch (InvocationTargetException e) {
            e.printStackTrace();
        } catch (NoSuchMethodException e) {
            e.printStackTrace();
        }

    }
}

　　执行结果为：

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原文地址：https://www.cnblogs.com/ajing2018/p/15917166.html