//filter过滤器
package filter;
import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
/**
* 网站访问计数器,初始值为5000
* @author Administrator
*
*/
public class MyFilter implements Filter {
//定义私有全局变量
private int count;
@Override
public void init(FilterConfig filterConfig) throws ServletException {
String param = filterConfig.getInitParameter("count");
//将值拿到,可以进行下一步的操作
count = Integer.valueOf(param);
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
//没访问一次页面,数量+1
count++;
//由于客户端发送的请求都是HTTP,所以将request转换成HttpServletRequest
HttpServletRequest req = (HttpServletRequest)request;
//通过会话得到计数
ServletContext context = req.getSession().getServletContext();
//修改计数值,count
context.setAttribute("count", count);
//过滤处理
chain.doFilter(request, response);
}
@Override
public void destroy() {
}
}
//web.xml配置
<!-- 过滤器声明 -->
<filter>
<!-- 过滤器名称 -->
<filter-name>myFilter</filter-name>
<!-- 过滤器完整类名 -->
<filter-class>filter.MyFilter</filter-class>
<init-param>
<param-name>count</param-name>
<param-value>5000</param-value>
</init-param>
</filter>
<!-- 过滤器映射 -->
<filter-mapping>
<!-- 过滤器名称 -->
<filter-name>myFilter</filter-name>
<!-- 过滤器URL映射 -->
<url-pattern>/filter.jsp</url-pattern>
</filter-mapping>
//jsp页面
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<!-- 通过application获取服务器中的count -->
您是本站的第<%=application.getAttribute("count") %>位访问
</body>
</html>
在服务器启动的情况下,访问的数量为5000+(默认为5000),但是如果重启服务器将重新从5000开始计数;
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