HTTP的request请求

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HTTP

概念

* 概念：Hyper Text Transfer Protocol 超文本传输协议
	* 传输协议：定义了，客户端和服务器端通信时，发送数据的格式
	* 特点：
		1. 基于TCP/IP的高级协议
		2. 默认端口号:80
		3. 基于请求/响应模型的:一次请求对应一次响应
		4. 无状态的：每次请求之间相互独立，不能交互数据

	* 历史版本：
		* 1.0：每一次请求响应都会建立新的连接
		* 1.1：复用连接

请求消息数据格式

请求消息：：客户端发送给服务器端的数据
* 请求消息数据格式
	1. 请求行
		请求方式 请求url 请求协议/版本
		GET /login.html	HTTP/1.1

		* 请求方式：
			* HTTP协议有7中请求方式，常用的有2种
				* GET：
					1. 请求参数在请求行中，在url后。
					2. 请求的url长度有限制的
					3. 不太安全
				* POST：
					1. 请求参数在请求体中
					2. 请求的url长度没有限制的
					3. 相对安全
	2. 请求头：客户端浏览器告诉服务器一些信息
		请求头名称: 请求头值
		* 常见的请求头：
			1. User-Agent：浏览器告诉服务器，我访问你使用的浏览器版本信息
				* 可以在服务器端获取该头的信息，解决浏览器的兼容性问题

			2. Referer：http://localhost/login.html
				* 告诉服务器，我(当前请求)从哪里来？
					* 作用：
						1. 防盗链：
						2. 统计工作：
	3. 请求空行
		空行，就是用于分割POST请求的请求头，和请求体的。
	4. 请求体(正文)：
		* 封装POST请求消息的请求参数的

	* 字符串格式：
		POST /login.html	HTTP/1.1
		Host: localhost
		User-Agent: Mozilla/5.0 (Windows NT 6.1; Win64; x64; rv:60.0) Gecko/20100101 Firefox/60.0
		Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
		Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
		Accept-Encoding: gzip, deflate
		Referer: http://localhost/login.html
		Connection: keep-alive
		Upgrade-Insecure-Requests: 1
		
		username=zhangsan

Request

1. request对象和response对象的原理
	1. request和response对象是由服务器创建的。我们来使用它们
	2. request对象是来获取请求消息，response对象是来设置响应消息

2. request对象继承体系结构：	
	ServletRequest		--	接口
		|	继承
	HttpServletRequest	-- 接口
		|	实现
	org.apache.catalina.connector.RequestFacade 类(tomcat)

request获取请求消息数据

3. request功能：
	1. 获取请求消息数据
		1. 获取请求行数据
			* GET /day14/demo1?name=zhangsan HTTP/1.1
			* 方法：
				1. 获取请求方式 ：GET
					* String getMethod()  
				2. (*)获取虚拟目录：/day14
					* String getContextPath()
				3. 获取Servlet路径: /demo1
					* String getServletPath()
				4. 获取get方式请求参数：name=zhangsan
					* String getQueryString()
				5. (*)获取请求URI：/day14/demo1
					* String getRequestURI():		/day14/demo1
					* StringBuffer getRequestURL()  :http://localhost/day14/demo1

					* URL:统一资源定位符 ： http://localhost/day14/demo1	中华人民共和国
					* URI：统一资源标识符 : /day14/demo1					共和国
				
				6. 获取协议及版本：HTTP/1.1
					* String getProtocol()

				7. 获取客户机的IP地址：
					* String getRemoteAddr()
				
		2. 获取请求头数据
			* 方法：
				* (*)String getHeader(String name):通过请求头的名称获取请求头的值
				* Enumeration<String> getHeaderNames():获取所有的请求头名称
			
		3. 获取请求体数据:
			* 请求体：只有POST请求方式，才有请求体，在请求体中封装了POST请求的请求参数
			* 步骤：
				1. 获取流对象
					*  BufferedReader getReader()：获取字符输入流，只能操作字符数据
					*  ServletInputStream getInputStream()：获取字节输入流，可以操作所有类型数据
						* 在文件上传知识点后讲解

				2. 再从流对象中拿数据

获取请求行数据

package cn.itcase.web.request;

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;
/**
 * 演示Request对象的请求获取方式
 */
@WebServlet("/requestDemo1")
public class RequestDemo1 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1. 获取请求方式 ：GET
        String method = request.getMethod();
        System.out.println(method);

        // 2. (*)获取虚拟目录：/day14
        String contextPath = request.getContextPath();
        System.out.println(contextPath);

        //3. 获取Servlet路径: /demo1
        String servletPath = request.getServletPath();
        System.out.println(servletPath);

        //4. 获取get方式请求参数：name=zhangsan
        String queryString = request.getQueryString();
        System.out.println(queryString);

        //5. (*)获取请求URI：/day14/demo1
        String requestURI = request.getRequestURI();
        System.out.println(requestURI);
        StringBuffer requestURL = request.getRequestURL();
        System.out.println(requestURL);

        //6. 获取协议及版本：HTTP/1.1
        String protocol = request.getProtocol();
        System.out.println(protocol);

        //7. 获取客户机的IP地址：
        String remoteAddr = request.getRemoteAddr();
        System.out.println(remoteAddr);
    }
}

//------------------   http://localhost:8080/tomcat02_war_exploded/requestDemo1?a=1
GET
/tomcat02_war_exploded
/requestDemo1
a=1
/tomcat02_war_exploded/requestDemo1
http://localhost:8080/tomcat02_war_exploded/requestDemo1
HTTP/1.1
0:0:0:0:0:0:0:1

获取请求头数据

package cn.itcase.web.request;

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.util.Enumeration;

@WebServlet("/RequestDemo2")
public class RequestDemo2 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //演示获取请求头数据

        //1. 获取所有的请求头名称
        Enumeration<String> headerNames = request.getHeaderNames();
        //2. 遍历
        while (headerNames.hasMoreElements()){
            String name = headerNames.nextElement();
            //根据请求名称获取请求头的值
            String value = request.getHeader(name);
            System.out.println(name + "-----" + value);

        }

    }
}

//--------------------  http://localhost:8080/tomcat02_war_exploded//RequestDemo2?a=1
host-----localhost:8080
connection-----keep-alive
cache-control-----max-age=0
upgrade-insecure-requests-----1
user-agent-----Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36 Edg/87.0.664.66
accept-----text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
sec-fetch-site-----none
sec-fetch-mode-----navigate
sec-fetch-user-----?1
sec-fetch-dest-----document
accept-encoding-----gzip, deflate, br
accept-language-----zh-CN,zh;q=0.9,en;q=0.8,en-GB;q=0.7,en-US;q=0.6
cookie-----JSESSIONID=7B14C8B458E005F3B1A3CEBB2772E494

单个请求头数据的获取

package cn.itcase.web.request;

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.util.Enumeration;

@WebServlet("/RequestDemo3")
public class RequestDemo3 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //演示获取请求头数据 ：user-agent

        String agent = request.getHeader("user-agent");
        //判断agent
        if (agent.contains("Chrome")) {
            System.out.println("谷歌来了");
        } else if (agent.contains("Firefox")) {
            System.out.println("火狐来了");
        }

    }
}

单个请求头数据的获取

package cn.itcase.web.request;

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("/RequestDemo4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //演示获取请求头数据 ：referer

        String referer = request.getHeader("referer");
        System.out.println(referer);

        //防盗链
        if(referer != null){
            if(referer.contains("/tomcat02_war_exploded")){
                //正常访问
                System.out.println("播放电影。。。。");
            }else {
                //盗链
                System.out.println("想看电影吗？来优酷吧");
            }
        }

    }
}
//----------------login.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/demo4" method="GET">
        <input name="username">
        <input type="submit" value="提交">
    </form>
<hr>

<a href="/tomcat02_war_exploded/RequestDemo4">demo4</a>
</body>
</html>
    
//-------------------
http://localhost:8080/tomcat02_war_exploded/login.html
播放电影。。。。

盗链
在这里插入图片描述

获取请求体数据

package cn.itcase.web.request;

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.BufferedReader;
import java.io.IOException;

@WebServlet("/RequestDemo5")
public class RequestDemo5 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //获取请求消息体--请求参数

        //1 获取字符流
        BufferedReader br = request.getReader();
        //2 读取数据
        String line = null;
        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }


    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
}

//-------------------------- regist.html
<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>
    <form action="/tomcat02_war_exploded/RequestDemo5" method="post">
        <input type="text" placeholder="请输入用户名" name="username"><br>
        <input type="text" placeholder="请输入密码" name="password"><br>
        <input type="submit" value="注册">

    </form>
</body>
</html>
    
//------------------- 获取结果
username=zhangsan&password=123

在这里插入图片描述

其它功能

2. 其他功能：
	1. 获取请求参数通用方式：不论get还是post请求方式都可以使用下列方法来获取请求参数
		1. String getParameter(String name):根据参数名称获取参数值    username=zs&password=123
		2. String[] getParameterValues(String name):根据参数名称获取参数值的数组  hobby=xx&hobby=game
		3. Enumeration<String> getParameterNames():获取所有请求的参数名称
		4. Map<String,String[]> getParameterMap():获取所有参数的map集合

		* 中文乱码问题：
			* get方式：tomcat 8 已经将get方式乱码问题解决了
			* post方式：会乱码
				* 解决：在获取参数前，设置request的编码request.setCharacterEncoding("utf-8");

获取请求参数通用方式

在这里插入图片描述

regist2.html 可修改 method=“get” 为"post"

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>
    <form action="/tomcat02_war_exploded/RequestDemo6" method="get">   
        <input type="text" placeholder="请输入用户名" name="username"><br>
        <input type="text" placeholder="请输入密码" name="password"><br>
        <input type="submit" value="注册">

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

package cn.itcase.web.request;

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.BufferedReader;
import java.io.IOException;
import java.util.Enumeration;
import java.util.Map;
import java.util.Set;

@WebServlet("/RequestDemo6")
public class RequestDemo6 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //post请求参数

        //根据参数名称获取参数值
        String username = request.getParameter("username");
 /*       System.out.println("psot");
        System.out.println(username);
  */

        //根据参数名称获取参数值
        String[] hobbies = request.getParameterValues("hobby");
/*        for (String hobby : hobbies) {
           System.out.println(hobby);
       }
 */

        // 获取所有请求的参数名称
        Enumeration<String> parameterNames = request.getParameterNames();
 /*       while (parameterNames.hasMoreElements()){
            String name = parameterNames.nextElement();
            System.out.println(name);
            String value = request.getParameter(name);
            System.out.println(value);
            System.out.println("----------------");
        }

  */

        // 获取所有参数的map集合
        Map<String, String[]> parameterMap = request.getParameterMap();
        //遍历
        Set<String> keySet = parameterMap.keySet();
        for (String name : keySet) {

            //获取键与值
            String[] values = parameterMap.get(name);
            System.out.println(name);
            for (String value : values) {
                System.out.println(value);
            }

            System.out.println("---------------------");
        }

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //get请求参数

 /*       //根据参数名称获取参数值
        String username = request.getParameter("username");
        System.out.println("get");
        System.out.println(username);
  */
        //以上代码可简写为此
        this.doPost(request,response);
    }
}

请求转发

	2. 请求转发：一种在服务器内部的资源跳转方式
		1. 步骤：
			1. 通过request对象获取请求转发器对象：RequestDispatcher getRequestDispatcher(String path)
			2. 使用RequestDispatcher对象来进行转发：forward(ServletRequest request, ServletResponse response) 

		2. 特点：
			1. 浏览器地址栏路径不发生变化
			2. 只能转发到当前服务器内部资源中。
			3. 转发是一次请求

代码

package cn.itcase.web.request;

import javax.servlet.RequestDispatcher;
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("/RequestDemo8")
public class RequestDemo8 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("demo8888被访问了");
        // 转发到demo9资源
/*
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/RequestDemo9");
        requestDispatcher.forward(request,response);
        */
        request.getRequestDispatcher("/RequestDemo9").forward(request, response);

    }


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

package cn.itcase.web.request;

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("/RequestDemo9")
public class RequestDemo9 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("demo9999被访问了");
    }


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

访问路径：

http://localhost:8080/tomcat02_war_exploded/RequestDemo8

输出结果：

demo8888被访问了
demo9999被访问了

共享数据：

	3. 共享数据：
		* 域对象：一个有作用范围的对象，可以在范围内共享数据
		* request域：代表一次请求的范围，一般用于请求转发的多个资源中共享数据
		* 方法：
			1. void setAttribute(String name,Object obj):存储数据
			2. Object getAttitude(String name):通过键获取值
			3. void removeAttribute(String name):通过键移除键值对

package cn.itcase.web.request;

import javax.servlet.RequestDispatcher;
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("/RequestDemo8")
public class RequestDemo8 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        System.out.println("demo8888被访问了");

        //存储数据到request域中
        request.setAttribute("msg","hello");


        // 转发到demo9资源
/*
        RequestDispatcher requestDispatcher = request.getRequestDispatcher("/RequestDemo9");
        requestDispatcher.forward(request,response);
        */

        request.getRequestDispatcher("/RequestDemo9").forward(request, response);

    }


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

package cn.itcase.web.request;

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("/RequestDemo9")
public class RequestDemo9 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //获取数据
        Object msg = request.getAttribute("msg");
        System.out.println(msg);

        System.out.println("demo9999被访问了");
    }


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

访问路径：

http://localhost:8080/tomcat02_war_exploded/RequestDemo8

输出结果：

demo8888被访问了
hello
demo9999被访问了

ServletContext

	4. 获取ServletContext：
		* ServletContext getServletContext()

package cn.itcase.web.request;

import javax.servlet.ServletContext;
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("/RequestDemo10")
public class RequestDemo10 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //获取数据
        ServletContext servletContext = request.getServletContext();
        System.out.println(servletContext);
    }


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

//-----------------------------
org.apache.catalina.core.ApplicationContextFacade@545b4cf2

习题

项目文件： G:\javaEE_Http\http_web\web_test

* 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

在这里插入图片描述

项目目录

在这里插入图片描述

1 login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/web_test_war_exploded/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>

开启页面注意：不要使用ie

http://localhost:8080/web_test_war_exploded/login.html

2 引用的jar包

目录结构自己创建
在这里插入图片描述

3 数据库JDBC配置文件

driverClassName=com.mysql.jdbc.Driver
url=jdbc:mysql://127.0.0.1:3306/day14
username=root
password=root
# 初始化连接数
initialSize=5
# 最大连接数
maxActive=10
# 最大等待时间
maxWait=3000

4 数据库数据


CREATE DATABASE day14;   -- 创建day14 数据库
USE day14;               -- 进入day14 数据库
CREATE TABLE USER(       -- 创建表

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

insert into user values(null,"zhangsan","123456");

5 创建包itcast.domain,创建类User

package itcast.domain;

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

    public Integer getId() {
        return id;
    }

    public void setId(Integer 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 + '\'' +
                '}';
    }
}

6 创建包cn.itcast.util,编写工具类JDBCUtils

package 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，使用Durid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;
    }

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

7 创建包itcast.dao,创建类UserDao,提供login方法

package itcast.dao;

import itcast.domain.User;
import 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表中的类
 */
public class UserDao {

    //声明JdbcTemplate对象共用
    private JdbcTemplate template = new JdbcTemplate(JDBCUtils.getDataSource());

    /**
     * 登录方法
     *
     * @param loginUser 只有用户和密码
     * @return user包含用户全部数据
     */
    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.class),
                    loginUser.getUsername(), loginUser.getPassword());
            return user;
        } catch (DataAccessException e) {     // 增加 try..catch.. 测试账号密码错误，查询结果为0时会报错
            e.printStackTrace();              // 记录日志
            return null;
        }
    }
}

8 创建包itcast.test,创建类UserDaoTest,测试login方法

package itcast.test;


import itcast.dao.UserDao;
import itcast.domain.User;
import org.junit.Test;

public class UserDaoTest {

    @Test
    public void testLogin() {
        User loginuser = new User();
        loginuser.setUsername("zhangsan");
        loginuser.setPassword("1234561");

        UserDao dao = new UserDao();
        User user = dao.login(loginuser);

        System.out.println(user);
    }

}  
// 测试输入账号密码正确
// 测试输入账号错误       -- UserDao 中增加了增加 try..catch.. 测试账号密码错误，查询结果为0时会报错

9 创建包itcast.web.servlet,处理登录请求

LoginServlet

package itcast.web.servlet;

import itcast.dao.UserDao;
import 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 {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        // 1 设置编码
        req.setCharacterEncoding("utf-8");

        /*
        // 2 获取请求的参数
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        // 3 封装user对象
        User loginUser = new User();
        loginUser.setUsername(username);
        loginUser.setPassword(password);
         */

        // 使用 commons-beanutils-1.8.0.jar
        // 2 获取所有的请求参数
        Map<String, String[]> map = req.getParameterMap();
        // 3 创建User对象
        User loginUser = new User();
        // 3.2 使用BeanUtils 封装
        try {
            BeanUtils.populate(  ,map);                         //org.apache.commons.beanutils.BeanUtils;
        } 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){
            //登陆失败
            req.getRequestDispatcher("/failServlet").forward(req,resp);
        }else {
            // 登录成功
            // 存储数据
            req.setAttribute("user",user);
            // 转发
            req.getRequestDispatcher("/successServlet").forward(req,resp);
        }
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        this.doGet(req,resp);
    }
}

SuccessServlet

package itcast.web.servlet;

import 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) {    //防止空指针异常
            //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);
    }
}

FailServlet

package 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);
    }
}