Servlet学习之Response和Request

这个放在前面说，说一下请求转发和重定向的的异同

相同点:

都会是页面发生跳转

不同点：

请求转发：url的地址不会发生变化
重定向：url的地址跳转到需要转发的页面

Response（重定向）

下边看一个具体的例子

 <servlet>
        <servlet-name>request</servlet-name>
        <servlet-class>com.wu.response.RequestServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>request</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

<%--index.jsp页面--%>
<html>
<body>
<h2>Hello World!</h2>
    
<%--这里提交的路径需要找到项目路径--%>
<%--pageContext.request.contextPath 代表当前的项目--%>
<form action="${pageContext.request.contextPath}/login" method="post">
    用户名：<input type="text" name="username:"><br>
    密&nbsp;&nbsp码：<input type="password" name="password:" ><br>
    <input type="submit" name="提&nbsp;&nbsp交">

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

<%--success.jsp页面--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
    <title>Title</title>
</head>
<body>
    <h1>Success</h1>
</body>
</html>

package com.wu.response;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class RequestServlet extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        //重定向时候一定要注意 路径问题
        resp.sendRedirect("/rsp/success.jsp");
    }
}

启动之后进入到index.jsp页面，之后输入名字和密码之后点击提交按钮，此时页面就会跳转到success.jsp这个页面，而上边的url也会发生变化，此时的url地址是success.jsp的地址，而不是RequestServlet.java的地址。

在这里插入图片描述

Request（请求转发）

这个使用的方法是req.getRequestDispatcher("想要装发到的地址").forward(req,resp);

看一个具体的例子

 <servlet>
        <servlet-name>Login</servlet-name>
        <servlet-class>com.zkw.request.LoginServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>Login</servlet-name>
        <url-pattern>/login</url-pattern>
    </servlet-mapping>

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

<body>
    <div>
        <form action="${pageContext.request.contextPath}/login" method="post">
            用户名：<input type="text" name="username"><br>
            密&nbsp;&nbsp;码：<input type="password" name="pwd"><br>
            爱&nbsp;&nbsp;好：
            <input type="checkbox" name="hobbys" value="Python">Python
            <input type="checkbox" name="hobbys" value="Java">Java
            <input type="checkbox" name="hobbys" value="C">C
            <input type="checkbox" name="hobbys" value="C++">C++

            <br><br>
          <input type="submit">

        </for>
    </div>
</body>
</html>

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


package com.zkw.request;

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 {
       doPost(req, resp);
    }

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String username = req.getParameter("username");
        String pwd = req.getParameter("pwd");
        String[] hobbys = req.getParameterValues("hobbys");

        System.out.println(username);
        System.out.println(pwd);
        System.out.println(Arrays.toString(hobbys));

        //通过请求转发
        // 解释 / 代表当前的web应用
        req.getRequestDispatcher("/success.jsp").forward(req,resp);
    }
}