• 转发和重定向区别


    转发是服务器行为,重定向是客户端行为。转发耗时比重定向少。

    转发——>客户浏览器发送HTTP请求——>web服务器接受请求——>调用内部一个方法在容器内部完成请求处理和转发动作——>再将转发跳转到的那个网页资源返回给客户;  转发只能在同一个容器内完成 转发的时候浏览器地址是不会变的,在客户浏览器里只会显示第一次进入的那个网址或者路径,客户看不到这个过程,只是得到了想要的目标资源。转发行为浏览器只做了一次请求。(转发只能跳转一次)

    重定向——>客户浏览器发送HTTP请求——>web服务器接受请求后发送302状态码以及新的位置给客户浏览器——>客户浏览器发现是302响应,则自动再发送一个新的HTTP请求,请求指向新的地址(302:Found  临时移动,但资源只是临时被移动。即你访问网址A,但是网址A因为服务器端的拦截器或者其他后端代码处理的原因,会被重定向到网址B。)——>服务器根据此请求寻找资源发个客户;再客户浏览器中显示的是重定向之后的路径,客户可以看到地址的变化。重定向行为浏览器做了至少两次请求。(重定向可以跳转多次)

     

    从图解可以看出转发时客户端只发送了一次请求,而重定向时客户端需要发送至少两次请求。

    如生活实例(假如去办个证件):

    重定向:你先去了A局,A局的人说:“这个事情不归我们管,去B局”,然后,你就从A退了出来,自己乘车去了B局。 

    转发:你先去了A局,A局看了以后,知道这个事情其实应该B局来管,但是他没有把你退回来,而是让你坐一会儿,自己到后面办公室联系了B的人,让他们办好后,送了过来。

    一、转发:

    index.jsp

    <%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>Insert title here</title>
    </head>
    <body>
    <form action="second" method="get">
    <input type="submit" value="登陆 ">
    </form>
    </body>
    </html>
    Second.java

    package com.xianyadong.demo;

    import java.io.IOException;

    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;
    @WebServlet("/second")
    public class Second extends HttpServlet{
    private static final long serialVersionUID = 1L;


    public Second() {
    super();

    }
    public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException{
    System.out.println("=====");
    request.getRequestDispatcher("/welcome").forward(request, response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException{
    doGet(request, response);

    }


    }
    Welcome.java

    package com.xianyadong.demo;

    import java.io.IOException;
    import java.io.PrintWriter;

    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;

    @WebServlet("/welcome")
    public class Welcome extends HttpServlet {
    private static final long serialVersionUID = 1L;


    public Welcome() {
    super();

    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setCharacterEncoding("utf-8");
    response.setContentType("text/html;charset=utf-8");
    PrintWriter writer = response.getWriter();
    writer.println("<html>");
    writer.println("<body>欢迎"+"</body>");


    writer.println("</html>");
    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    doGet(request, response);
    }

    }
    浏览器点击登录去访问Second.java 然后Second通过转发返回给浏览器Welcome.java的内容。

    从图可以看出网站地址只会显示second不会出现welcome。

    二、重定向

    index.java 还用上面原来的

    Second.java

    package com.kaoshi.chongdingxiang;

    import java.io.IOException;
    import java.io.PrintWriter;

    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;


    @WebServlet("/second")
    public class Second extends HttpServlet {
    private static final long serialVersionUID = 1L;


    public Second() {
    super();

    }


    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }


    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    response.sendRedirect("welcome");
    }

    }
    Welcome.java

    package com.kaoshi.chongdingxiang;

    import java.io.IOException;
    import java.io.PrintWriter;

    import javax.servlet.ServletException;
    import javax.servlet.annotation.WebServlet;
    import javax.servlet.http.HttpServlet;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletResponse;


    @WebServlet("/welcome")
    public class Welcome extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public Welcome() {
    super();

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    response.setCharacterEncoding("utf-8");
    response.setContentType("text/html;charset=utf-8");
    PrintWriter writer = response.getWriter();
    StringBuffer requestURL = request.getRequestURL();
    writer.println(requestURL.toString());
    writer.println("<br>");
    int status = response.getStatus();
    writer.println(status);
    writer.println("<html>");
    writer.println("<body>欢迎"+"</body>");
    writer.println("</html>");
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    doGet(request, response);
    }

    }



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  • 原文地址:https://www.cnblogs.com/h-c-g/p/10617464.html
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