黑马day04 request&请求转发

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);
	}

}