ServletContext中的转发

客户端向服务器发送请求，服务器将请求进行转发，获得响应信息，客户端只发送一次请求，地址栏信息不变。

服务器接收类，进行转发

package com.itheima.zhuanfa;

import java.io.IOException;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ServletContextDemo3 extends HttpServlet{

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
//		转发
		//获得ServletContext对象
		ServletContext sc=getServletContext();
		System.out.println("转发前");
		resp.getOutputStream().write("before".getBytes());
		//获得转发器
		RequestDispatcher rd=sc.getRequestDispatcher("/Demo4");//得到请求转发器
		rd.forward(req,resp);
		/*
		 * 转发的特点：请求的地址栏不变，两者共享request和response对象
		 * 转发前和转发后的页面输出都不会发送到客户端
		 * 转发前不要刷新response中的内容，会吧response中的内容清空
		 */
		System.out.println("转发后");
		resp.getOutputStream().write("after".getBytes());

	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {

	}

}

转发到的类把这个类的信息传到客户端

package com.itheima.zhuanfa;

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 ServletContextDemo4 extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		resp.getOutputStream().write("转发成功，我来自Demo4".getBytes());
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {

	}

}