HttpServletRequest详解

HttpServletRequest

HttpServletRequest代表客户端的请求，用户通过http协议访问服务器，HTTP请求中的所有信息会被疯转到HttpServletRequest
通过这个Request方法可以获得客户端的所有信息

首先先看一下Request的一些方法

主要的方法是获取参数请求转发

获取前端传递的参数

注意
sendRedirect()方法进行重定向时，需要在前面加上项目路径

getRequestDispatcher()进行转发时，不需要加前面的项目路径

请求转发和重定向的区别

请求转发的时候，url不会发生变化；307
重定向的时候，url地址栏会发生变化；302

一般用request请求转发，response重定向

利用request实现模拟登陆页面的过程

LoginServlet

package com.lding.servlet;

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.util.Arrays;

/** * @program: javaweb-03-servlet * @description: * @author: 王丁 * @date: 2021-10-27 20:38 **/
public class LoginServlet extends HttpServlet { 
   
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { 
   
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");
        String username = req.getParameter("username");
        String password = req.getParameter("password");
        String[] hobbies = req.getParameterValues("hobby");
        System.out.println("==========");
        //后台接收中文乱码问题
        System.out.println(username);
        System.out.println(password);
        System.out.println(Arrays.toString(hobbies));
        System.out.println("==========");
        System.out.println(req.getContextPath());
        //通过请求转发
        //这里的/代表当前的web应用
        req.getRequestDispatcher("/success.jsp").forward(req,resp);
        //下面用response重定向的方法同样可以实现该功能，回顾一下对比一下印象更深刻
        //resp.sendRedirect("/rq/success.jsp");

    }

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

index.jsp

<%--
  Created by IntelliJ IDEA.
  User: apple
  Date: 2021/10/27
  Time: 8:37 PM
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登陆</title>
</head>
<body>
<h1>登陆</h1>
<div style="text-align: center">
<%--    这里表单表示的意思以post的方式提交表单，提交到我们login --%>
    <form action="${pageContext.request.contextPath}/login" method="post">
        用户名：<input type="text" name="username"> <br>
        密码：<input type="password" name="password"><br>
        爱好：
        <input type="checkbox" name="hobby" value="女孩">女孩
        <input type="checkbox" name="hobby" value="代码">代码
        <input type="checkbox" name="hobby" value="唱歌">唱歌
        <input type="checkbox" name="hobby" value="电影">电影
        <br>
        <input type="submit">
    </form>
</div>
</body>
</html>

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_3_1.xsd" version="3.1" metadata-complete="true">
    <servlet>
        <servlet-name>LoginServlet</servlet-name>
        <servlet-class>com.lding.servlet.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>LoginServlet</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>
</web-app>

success.jsp

<%--
  Created by IntelliJ IDEA.
  User: apple
  Date: 2021/10/27
  Time: 8:53 PM
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
<h1>登陆成功！</h1>
</body>
</html>