8、Javaweb_ServlethttpRequst

Servlet：

1. 概念
2. 步骤
3. 执行原理
4. 生命周期
5. Servlet3.0 注解配置
6. Servlet的体系结构
   Servlet -- 接口
       |
   GenericServlet -- 抽象类
       |
   HttpServlet -- 抽象类

* GenericServlet：将Servlet接口中其他的方法做了默认空实现，只将service()方法作为抽象
* 将来定义Servlet类时，可以继承GenericServlet，实现service()方法即可

   * HttpServlet：对http协议的一种封装，简化操作
       1. 定义类继承HttpServlet
       2. 复写doGet/doPost方法
测试服务器用到的HTML页面，action的路劲参数值,根据测试需要修改即可

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>注册页面</title>
</head>
<body>

    <form action="/requestDemo7" 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="checkbox" name="hobby" value="game">游戏
        <input type="checkbox" name="hobby" value="study">学习
        <br>

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

    </form>

</body>
</html>

测试类

@WebServlet("/demo1")
public class ServletDemo1 implements Servlet {


    @Override
    public void init(ServletConfig servletConfig) throws ServletException {

    }

    @Override
    public ServletConfig getServletConfig() {
        return null;
    }

    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("demo1....");
    }

    @Override
    public String getServletInfo() {
        return null;
    }

    @Override
    public void destroy() {

    }


}

@WebServlet("/demo2")
public class ServletDemo2 extends GenericServlet {
    @Override
    public void service(ServletRequest servletRequest, ServletResponse servletResponse) throws ServletException, IOException {
        System.out.println("demo2.....");
    }


}

@WebServlet("/demo3")
public class ServletDemo3 extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doGet....");
        System.out.println("demo4...");
    }
    private static void startThread(HttpServlet hs) {
        new HttpServlet(){};
    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("doPost...");
        System.out.println("demo4...");
        System.out.println(req.getHeader("User-Agent"));//Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:108.0) Gecko/20100101 Firefox/108.0
        System.out.println(req.getHeader("Referer"));//http://localhost/login.html
        System.out.println(req.getHeaderNames());
    }
}

7. Servlet相关配置
   1. urlpartten:Servlet访问路径
       1. 一个Servlet可以定义多个访问路径： @WebServlet({"/d4","/dd4","/ddd4"})
       2. 路径定义规则：
           1. /xxx：路径匹配
           2. /xxx/xxx:多层路径，目录结构
           3. *.do：扩展名匹配

//@WebServlet({"/d4","/dd4","/ddd4"})
//@WebServlet("/user/demo4")
//@WebServlet("/user/*")
//@WebServlet("/*")
@WebServlet("*.do")
public class ServletDemo4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("demo4...");
        System.out.println(req.getHeader("User-Agent"));
        System.out.println(req.getHeader("Referer"));

    }
    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("demo4...");
        System.out.println(req.getHeader("User-Agent"));
        System.out.println(req.getHeader("Referer"));

    }

}

HTTP：

* 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
   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：

           Accept:   信息格式:*/*   什么都可以
            Accept-Language:语言环境
            Accept-Encoding:压缩格式
            Connection:keep-alive   可以被复用,1.0版本则是断开值

获取请求头数据:user-agent

获取请求头数据:referer
   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

* 响应消息数据格式

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)

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()

@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 getMethod()
            2. (*)获取虚拟目录：/day14
                * String getContextPath()
            3. 获取Servlet路径: /requestDemo1
                * 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/requestDemo1
                * StringBuffer getRequestURL()  :http://localhost/day14/requestDemo1
            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()

         */
        //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();
        StringBuffer requestURL = request.getRequestURL();
        System.out.println(requestURI);
        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);
    }
}

       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

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

    }
}

请求头数据:user-agent

@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的浏览器版本
        if(agent.contains("Chrome")){
            //谷歌
            System.out.println("谷歌来了...");
        }else if(agent.contains("Firefox")){
            //火狐
            System.out.println("火狐来了...");
        }

    }
}

请求头数据:referer

@WebServlet("/requestDemo4")
public class RequestDemo4 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    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);//http://localhost/day14/login.html

        //防盗链
        if(referer != null ){
            if(referer.contains("://localhost")){
                //正常访问
               // System.out.println("播放电影....");
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("播放电影....");
            }else{
                //盗链
                //System.out.println("想看电影吗？来优酷吧...");
                response.setContentType("text/html;charset=utf-8");
                response.getWriter().write("想看电影吗？来优酷吧...");
            }
        }


    }
}

       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

@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 {
    }
}

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");

@WebServlet("/requestDemo6")
public class RequestDemo6 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //post 获取请求参数

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

       //根据参数名称获取参数值的数组
        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) {
            
            //获取键获取值
            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 获取请求参数
/*
        //根据参数名称获取参数值
        String username = request.getParameter("username");
        System.out.println("get");
        System.out.println(username);*/

        this.doPost(request,response);
    }
}

解决post获取乱码问题

@WebServlet("/requestDemo7")
public class RequestDemo7 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //1.设置流的编码
        request.setCharacterEncoding("utf-8");

        //获取请求参数username
        String username = request.getParameter("username");

        System.out.println(username);
    }

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

        this.doPost(request,response);
    }
}

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

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

加载页面1,setAttribute存储数据

@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);
        */

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

        request.getRequestDispatcher("/requestDemo9").forward(request,response);
        //request.getRequestDispatcher("http://www.itcast.cn").forward(request,response);

    }

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

        this.doPost(request,response);
    }
}

跳转页面2,getAttitude获取已存储数据

@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);
    }
}

4. 获取ServletContext：
* ServletContext getServletContext()

@WebServlet("/requestDemo10")
public class RequestDemo10 extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {


        ServletContext servletContext = request.getServletContext();

        System.out.println(servletContext);

    }

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

        this.doPost(request,response);
    }
}

案例：用户登录

* 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

* 分析

* 开发步骤
1. 创建项目，导入html页面，配置文件，jar包

commons-logging-1.2.jar
druid-1.0.9.jar
mchange-commons-java-0.2.12.jar
mysql-connector-java-8.0.18.jar
spring-beans-5.0.0.RELEASE.jar
spring-core-5.0.0.RELEASE.jar
spring-jdbc-5.0.0.RELEASE.jar
spring-tx-5.0.0.RELEASE.jar

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

jar包

spring-tx-5.0.0.RELEASE.jar
spring-jdbc-5.0.0.RELEASE.jar
spring-core-5.0.0.RELEASE.jar
spring-beans-5.0.0.RELEASE.jar
mysql-connector-java-8.0.18.jar
druid-1.0.9.jar
mchange-commons-java-0.2.12.jar
commons-logging-1.2.jar
   2. 创建数据库环境
       CREATE DATABASE day14;
       USE day14;
       CREATE TABLE USER(

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

        3. 创建包cn.itcast.domain,创建类User
       package cn.itcast.domain;
       /**
       * 用户的实体类
       */

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 + '\'' +
                '}';
    }
}

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 javax.xml.crypto.Data;
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 (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对象共用
    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
            /* <T> T
queryForObject(String sql, RowMapper<T> rowMapper, Object... args)
查询给定的SQL，从SQL创建一个准备好的语句和一个要绑定到查询的参数列表，通过RowMapper将单个结果行映射到结果对象。
            * */
            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 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);*/
        //2.获取所有请求参数
        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(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){
            //登录失败
            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);
    }
}

7. 编写FailServlet和SuccessServlet类

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);
    }
}

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);
    }
}

8. login.html中form表单的action路径的写法
* 虚拟目录+Servlet的资源路径

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

9. BeanUtils工具类，简化数据封装
* 用于封装JavaBean的

导入jar包        commons-beanutils-1.8.0.jar
        1. JavaBean：标准的Java类
           1. 要求：
               1. 类必须被public修饰
               2. 必须提供空参的构造器
               3. 成员变量必须使用private修饰
               4. 提供公共setter和getter方法
           2. 功能：封装数据

2. 概念：
           成员变量：
           属性：setter和getter方法截取后的产物
               例如：getUsername() --> Username--> username

3. 方法：
           1. setProperty()        给set方法赋值值
           2. getProperty()        通过get方法获取值
           3. populate(Object obj , Map map):将map集合的键值对信息，封装到对应的JavaBean对象中

测试类1

package cn.itcast.test;

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

public class UserDaoTest {



    @Test
    public void testLogin(){
        User loginuser = new User();
        loginuser.setUsername("zhangsan");
        loginuser.setPassword("123");


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

        System.out.println(user);
    }
}

测试getProperty

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,"hehe","male");
            System.out.println(user);

            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();
        }





    }
}