servlet中servletContext的五大作用（三）

1.    获取web的上下文路径

2.    获取全局的参数

3.    作为域对象使用

4.    请求转发

5.    读取web项目的资源文件

package day10.about_servletcontext.scope;

import java.io.IOException;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
/**
 * 【context对象的作用-3】：域对象
 * @author mzy
 *		域对象是什么？域对象的作用？
 *		在web中我们经常需要在两个servlet之间传递信息
 * 但是通过重定向的话：
 *		通过response.sendReirect("/servlet2?name=eric");
 *		这种方式弊端很大：
 *		这种方式的本质就是通过get方式进行数据传输的
 *
 * 现在ServletContext是我们学习的第一个域对象：
 * 
 * 域对象负责到servlet中获取数据
 * 和将数据传输到指定的地方
 * 其中提供了两个方法进行这种操作： 
 * setAttribute("name", Object);
 * getAttribute("name");
 */	
public class ContextDemo03_ScopeDemo01 extends HttpServlet {

	private static final long serialVersionUID = -4001884291361193466L;

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
		ServletContext context = this.getServletContext();
		context.setAttribute("name", "mzy");
		System.out.println("name属性已经保存到context中...");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
	}
}

查看域对象中Attribute的servlet：

package day10.about_servletcontext.scope;

import java.io.IOException;

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 ContextDemo03_ScopeDemo02 extends HttpServlet {

	private static final long serialVersionUID = 880491464311792192L;

	public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
		ServletContext context = this.getServletContext();
		String name = (String)context.getAttribute("name");
		System.out.println(name);
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
		request.setCharacterEncoding("utf-8");
		response.setContentType("text/html;charset=utf-8");
		
	}

}