Java Web从入门到精通 明日科技 例9.3创建一个过滤器,实现网站计数的功能光盘位置TM\sl\9\1
过滤器部分代码
.........
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException
{
// TODO Auto-generated method stub
count++;
HttpServletRequest req=(HttpServletRequest)request;
ServletContext context=req.getSession().getServletContext();
context.setAttribute("count", count);
chain.doFilter(request, response);
}
@Override
public void init(FilterConfig arg0) throws ServletException
{
// TODO Auto-generated method stub
System.out.println("CountFilter is already started");
String param=arg0.getInitParameter("count");
count=Integer.valueOf(param);
System.out.println(count);//
}

}
web.xml
......
<filter>
<filter-name>CountFilter</filter-name>
<filter-class>com.gaoxin.CountFilter</filter-class>
<init-param>
<param-name>count</param-name>
<param-value>5000</param-value>
</init-param>
</filter>
<filter-mapping>
<filter-name>CountFilter</filter-name>
<url-pattern>/CountFilter</url-pattern>
</filter-mapping>
</web-app>
index.jsp
<body>
<h2>
欢迎观临<br>
您是本站的第【
<%=application.getAttribute("count") %>
】位访客!
</h2>
</body>
结果是这样

这是目录结构
