【JavaEE企业应用实战学习记录】Filter

 1 package sanglp.servlet;
 2 
 3 import javax.servlet.*;
 4 import javax.servlet.annotation.WebFilter;
 5 import javax.servlet.http.HttpServletRequest;
 6 import java.io.IOException;
 7 
 8 /**
 9  * Created by Administrator on 2016/10/5.
10  */
11 @WebFilter(filterName = "log", urlPatterns={"/*"} )
12 public class LogFilter  implements Filter {
13 
14     //用于访问Filter的配置信息
15     private FilterConfig config;
16 
17 
18     @Override
19     public void init(FilterConfig filterConfig) throws ServletException {
20         this.config=filterConfig;
21     }
22 
23     @Override
24     public void destroy() {
25         this.config=null;
26     }
27 
28     @Override
29     public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
30         //对于用户请求进行预处理
31         //获取ServletContext对象  用于记录日志
32         ServletContext context=this.config.getServletContext();
33         long before=System.currentTimeMillis();
34         System.out.println("开始过滤");
35         //将请求转换成HttpServletRequest
36         HttpServletRequest hrequest=(HttpServletRequest) servletRequest;
37         //输出提示信息
38         System.out.println("Filter已经截获到用户的请求的地址"+hrequest.getServletPath());
39         //Filter只是链式处理，请求依然放到目的地址
40         filterChain.doFilter(servletRequest, servletResponse);
41         //响应执行后处理
42         long  after=System.currentTimeMillis();
43         System.out.println("过滤结束");
44         System.out.println("请求被定位到"+hrequest.getRequestURI()+"所花的时间为："+(after-before));
45     }
46 }