Request object application (request forwarding and obtaining parameters)

I. Introduction

The request and response are opposites. This technical blog mainly explains the request object: HttpServletRequest
This object represents the client request . The user accesses the server through the http protocol, and all the information in the Http request will be encapsulated in the
HttpServletRequest. Through the methods of this object , all the information of the client can be obtained . E.g:

Insert picture description here In fact, these methods use very few scenarios.

Two, two key application scenarios

Get the parameters passed by the front end

Insert picture description here

Request forwarding The
request forwarding code is as follows:

package com.xu.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;

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[] hobbys = req.getParameterValues("hobbys");
        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(hobbys));
        System.out.println("=======================================================");

        //通过请求转发  getContextPath()返回的是tomcat中配置的虚拟路径
        //注意：这里的/代表当前的web应用
        req.getRequestDispatcher("/success.jsp").forward(req,resp);

    }

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

Landing page code:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录</title>
</head>
<body>
<h1>登录</h1>

<div>
    <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="hobbys" value="女孩">女孩
        <input type="checkbox" name="hobbys" value="代码">代码
        <input type="checkbox" name="hobbys" value="唱歌">唱歌
        <input type="checkbox" name="hobbys" value="电影">电影
        <br>
        <input type="submit">
    </form>
</div>
</body>
</html>

The code of the page visited after forwarding:

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>成功</title>
</head>
<body>
    <h1>登陆成功</h1>
</body>
</html>