黑马day04 request&请求转发

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到此为止：已经学习了两个域对象：

servletContext:web应用

request:仅仅用于同一个请求

作用范围:整个请求链上
生命周期:当服务器收到一个请求,创建出代表请求的request对象,request开始.当请求结束,服务器销毁代表请求的request对象,request域结束.
作用:在整个请求链范围内共享数据,通常我们在Servlet中处理好的数据会存入request域后请求转发到jsp页面来进行展示

setAttribute
getAttribute
removeAttribute

1.下面的例子既使用了域对象也使用了请求转发Demo1(在request中放了一个对象)转发到Demo2

package cn.itheima.request;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;/** * 请求转发 * @author Administrator * */public class Demo1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset=utf-8");request.setAttribute("description", "李卫康--哈哈好自恋");request.getRequestDispatcher("/servlet/Demo2").forward(request, response);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

2.在Demo2中取出request域中的值并输出打印到浏览器中...

package cn.itheima.request;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class Demo2 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String str = (String) request.getAttribute("description");response.getWriter().write(str);}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

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