JavaWeb请求转发！RequestDispatcher，补充：重定向

一、RequestDispatcher：

解释：getRequestDispatcher ().forward (request.response)这个语句意思是将客户端的请求转向(forward)到getRequestDispatcher()方法中参数定义的页面或者链接。

二、代码解释：

①：附：源码！源码图！

package com.laugh.servlet;

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

public class ForwardRequests extends Helloservlet{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        ServletContext Context = this.getServletContext();
        System.out.println("我进来喽！转发是不会改变访问路径的呦，重定向路径会发生改变！");
        //请求转发
        //RequestDispatcher requestDispatcher = Context.getRequestDispatcher("/url"); //转发的请求路径
        //requestDispatcher.forward(req,resp); //调用forward 实现上面的请求转发
        //合并请求转发  getRequestDispatcher的括号里面写 转发的地址
        Context.getRequestDispatcher("/url").forward(req,resp);

    }

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

②：web.xml配置 附：源码！源码图！

<?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_4_0.xsd"
         version="4.0">


    <!--我这个头是新的-->
    <!--设置web初始化参数-->
    <context-param>
        <param-name>url</param-name>
        <param-value>https://www.cnblogs.com/superyonng</param-value>
    </context-param>


    <!--我是提供获得初始化路径的方法 InitServlet-->
    <servlet>
        <servlet-name>url</servlet-name>
        <servlet-class>com.laugh.servlet.InitServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>url</servlet-name>
        <url-pattern>/url</url-pattern>
    </servlet-mapping>


    <!--合并请求转发 ForwardRequests-->
    <servlet>
        <servlet-name>mergs</servlet-name>
        <servlet-class>com.laugh.servlet.ForwardRequests</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>mergs</servlet-name>
        <url-pattern>/mergs</url-pattern>
    </servlet-mapping>


</web-app>

③：运行结果：

重点：

重定向：补充

package com.laugh;

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 redirectServel extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        resp.sendRedirect("/FileOutputStream_war/yzm");
    }

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

<servlet>
        <servlet-name>yzm</servlet-name>
        <servlet-class>com.laugh.YanZhengMa</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>yzm</servlet-name>
        <url-pattern>/yzm</url-pattern>
    </servlet-mapping>

    <servlet>
        <servlet-name>redirectServel</servlet-name>
        <servlet-class>com.laugh.redirectServel</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>redirectServel</servlet-name>
        <url-pattern>/red</url-pattern>
    </servlet-mapping>

第一步：我们所请求的路径

http://localhost:8080/FileOutputStream_war/red
//解释：http://localhost:8080/   为本地路径；FileOutputStream_war  为项目名称；  red   为web.xml配置

第二步：查看路径(当执行red的时候，重定向会给我们改变路径)

http://localhost:8080/FileOutputStream_war/yzm