forward请求转发

请求转发（forward）：一种服务器内部的资源跳转方式

实现方式：

reg.getRequestDispatcher("要跳转的路径").forward(req,resp);

 

创建两个Servlet，并配置他们的访问路径

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
@WebServlet("/d3")
public class ServletForward3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("d3.........");
        req.getRequestDispatcher("/d4").forward(req,resp);
    }
 
}

通过上面的程序，请求转发给下面的程序

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
@WebServlet("/d4")
public class ServletForward4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("d4.......");
    }
 
}

 

最后输出    d3.........

                  d4............

请求转发资源之间共享数据：使用Request对象

void  setAttribute（String name，Object  o）    存储数据到request域中。

Object getAttribute(String name)  根据键，获取值

void removeAttribute(String name)  根据键，删除键值对

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
@WebServlet("/d3")
public class ServletForward3 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("d3.........");
        req.setAttribute("张三","男");
        req.getRequestDispatcher("/d4").forward(req,resp);  //数据存入域
    }
}

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
 
@WebServlet("/d4")
public class ServletForward4 extends HttpServlet {
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("d4.......");
        System.out.println(req.getAttribute("张三"));// 通过键获取域中的值
 
    }
 
}

 最后输出 ：男 

共享数据就成功了

 请求转发的特点：

浏览器地址栏路径不发生变化

只能请求转发到当前服务器的内部资源

一次请求，可以转发的资源之间使用request共享数据