JavaWeb-HttpServletRequest举例解析-优快云博客

HttpServletRequest

HttpServletRequest代表客户端的请求，用户通过Http协议访问服务器，Http请求中的所有信息都会被封装到HttpServletRequest，通过这个HttpServletRequest的方法，获取客户的信息。

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小例子：

RequestServlet

package com.edwin.servlet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
 * @author Edwin D
 * @date 2020.6.4 上午 9:16
 */
public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        请求处理
        System.out.println("请求成功！");
        String Un = req.getParameter("Username");
        String Pwd = req.getParameter("Password");
        System.out.println(Un + ":" + Pwd);

//        重定向的时候一定要注意路径问题，否则极其容易出现404。
//        404代表路径问题，代码正常。而500则代表代码问题。
        resp.sendRedirect("/response_war/JumpSuccess.jsp");
    }

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

初始化的Jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<body>
<h2>Hello World!</h2>
<%--这里提价的路径，需要寻找到项目的路径--%>
<%--这里的${pageContext.request.contextPath}代表当前的项目    --%>
<form action="${pageContext.request.contextPath}/Request" method="get">
    用户名：<input type="text" name="Username">   <br>
    密码：<input type="password" name="Password"> <br>
    <input type="submit">
</form>
</body>
</html>

跳转的Jsp

<%--
  Created by IntelliJ IDEA.
  User: 元
  Date: 2020.6.4
  Time: 上午 9:33
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Success</title>
</head>
<body>
<h1>Success Jump!</h1>
</body>
</html>

xml:

<servlet>
    <servlet-name>Request</servlet-name>
    <servlet-class>com.edwin.servlet.RequestServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Request</servlet-name>
    <url-pattern>/Request</url-pattern>
</servlet-mapping>

输出效果：

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跳转：

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获取参数，请求转发

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getParameter()//适用于String
getParameterValues()//适用于数组

代码举例：
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LoginServlet:

package com.edwin.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;
/**
 * @author Edwin D
 * @date 2020.6.4 下午 12:50
 */
public class LoginServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
//        控制台，网页接受到中午乱码问题。
        req.setCharacterEncoding("UTF-8");
        resp.setCharacterEncoding("UTF-8");

        String Un = req.getParameter("Username");
        String Pwd = req.getParameter("Password");
        String[] hobbys = req.getParameterValues("hobbys");
        System.out.println("++++++++++++++++++++++++++++++++++");
        System.out.println(Un);
        System.out.println(Pwd);
        System.out.println(Arrays.toString(hobbys));
        System.out.println("++++++++++++++++++++++++++++++++++");

        System.out.println(req.getContextPath());
//        通过请求转发
//        这里的“/”代表了当前Web应用。
        req.getRequestDispatcher("/Success.jsp").forward(req,resp);
    }

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

Jsp1:

<%--
  Created by IntelliJ IDEA.
  User: 元
  Date: 2020.6.4
  Time: 上午 12:48
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>登录</title>
</head>
<body>
    <h1>登录</h1>
        <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="跑步">跑步
            <input type="checkbox" name="hobbys" value="游泳">游泳
            <input type="checkbox" name="hobbys" value="篮球">篮球
            <input type="checkbox" name="hobbys" value="约会">约会
            <br>
            <input type="submit">
        </form>
</body>
</html>

Jsp2:

<%--
  Created by IntelliJ IDEA.
  User: 元
  Date: 2020.6.4
  Time: 下午 3:26
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Success</title>
</head>
<body>
<h1>登录成功</h1>
</body>
</html>

Xml:

<servlet>
    <servlet-name>Login</servlet-name>
    <servlet-class>com.edwin.servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>Login</servlet-name>
    <url-pattern>/Login</url-pattern>
</servlet-mapping>