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
