servlet学习笔记_ServletContext
1 Web应用共享数据区ServletContext接口
1.1 Servlet容器何时创建ServeltContext接口实现类ServletContext接口表示一个web应用的上下文。可以想象成一个web一个能用的共享数据区域，该区域保存整个web共享数据。
1.2 如何获得ServletContext接口实例当一个web应用启动的时候，就会创建该ServletContext接口的实现类。我们可以在根据需求，读写ServletContext这个web共享区的数据，那么如何获得ServletContext这个实例呢？下面提供了两种方法
1.3 一个计数器实例方法1：
可以通过ServletConfig接口的getServletContext()方法获得
方法2：
通过GenericServlet抽象类的getServletContext()方法获得，不过这个方法其实也是调用了ServletConfig的getServletContext()方法
在GenericServlet.java中public ServletConfig getServletConfig() { return config; } public ServletContext getServletContext() { return getServletConfig().getServletContext(); }
1 楼 脑袋雷劈的 2009-02-18 resp.setContentType("text/html;utf-8");写这句，有时候不起作用。package servletcontext;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.ServletContext;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class CounterServlet extends HttpServlet{public void doGet(HttpServletRequest request, HttpServletResponse response){try{response.setCharacterEncoding("gb2312");//获取ServletContext接口的实现类ServletContext sc = super.getServletContext();Integer count = (Integer) sc.getAttribute("count");if(null == count){count = new Integer(1);}else{count = new Integer(count.intValue()+1);}sc.setAttribute("count", count);PrintWriter out = response.getWriter();out.print("<body>");out.print("你登录的次数是："+count.intValue());out.print("</body>");out.close();} catch (IOException e){e.printStackTrace();}}public void doPost(HttpServletRequest request, HttpServletResponse response){doGet(request,response);}}?
<?xml version="1.0" encoding="UTF-8"?><web-app version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"> <servlet> <servlet-name>CountServlet</servlet-name> <servlet-class>servletcontext.CounterServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>CountServlet</servlet-name> <url-pattern>/count</url-pattern> </servlet-mapping> </web-app>??
