forward：转发；redirect：重定向。区别如下：

浏览器 url 地址显示不同

服务端通过 forward 返回，浏览器 url 地址不会发生变化；服务器通过 redirect 返回，浏览器会重新请求， url 地址会发生变化

前后台两者页面跳转的处理方式不同

forward 跳转页面，是服务端进行页面跳转加载(include)新页面，直接返回到浏览器；redirect 跳转页面，是服务端返回新的 url 地址，浏览器二次发出 url 请求

参数携带情况不一样

forward 跳转页面，会共享请求的参数到新的页面；redirect 跳转页面，属于一次全新的 http 请求，无法共享上一次请求的参数

http 请求次数不同

forward 1次；redirect 2次

新目标地址范围不同

forward 必须是同一个应用内的某个资源；redirect 的新地址可以是任意地址

基于 servlet 实现

test servlet

package constxiong;

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;

/**

* test servlet

* @author ConstXiong

* @date 2019-06-26 10:00:34

*/

@WebServlet("/test")

public class TestServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

public TestServlet() {

}

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

response.getWriter().write("This is test.");

}

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

}

}

请求返回

redirect servlet

package constxiong;

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;

/**

* redirect servlet

* @author ConstXiong

* @date 2019-06-26 10:00:34

*/

@WebServlet("/redirect")

public class RedirectServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

public RedirectServlet() {

}

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

response.sendRedirect("http://www.baidu.com");

}

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

}

}

请求返回

forward servlet

package constxiong;

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;

/**

* forward servlet

* @author ConstXiong

* @date 2019-06-26 10:00:34

*/

@WebServlet("/forward")

public class ForwardServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

public ForwardServlet() {

}

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

request.getRequestDispatcher("/test").forward(request, response);//forward 跳转到 test 请求

}

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

}

}

请求返回