4.ServletContext（服务器全局变量）的使用

      在Sevlet中有时会用到服务器的全局变量，本节内容是如何使用服务器的全局变量（ServletContext）。Servlet中通过方法getServletContext()可以得到ServletContext实例，通过该实例可以设置和获取服务器的全局变量。

      示例代码如下：

package com.taoistwar.jsp.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

@SuppressWarnings("serial")
public class TestServletContext extends HttpServlet {

	@Override
	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		ServletContext application = this.getServletContext();
		Integer i = (Integer) application.getAttribute("hitCount");
		if (i == null) {
			i = new Integer(1);
		}
		application.setAttribute("hitCount", i++);
		PrintWriter out = response.getWriter();
		out.println(i);
	}

	@Override
	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

   配置文件：

<servlet>
  	<servlet-name>TestServletContext</servlet-name>
  	<servlet-class>com.taoistwar.jsp.servlet.TestServletContext</servlet-class>
  </servlet>
  <servlet-mapping>
  	<servlet-name>TestServletContext</servlet-name>
  	<url-pattern>/TestServletContext</url-pattern>
  </servlet-mapping>