java filter过滤器的配置

　　Web.xml配置，以下字段放在servlet下

 <filter>
  <filter-name>sessionFilter</filter-name>
  <filter-class>com.FlyPig.util.filter_session</filter-class>
 </filter>

 <filter-mapping>
  <filter-name>sessionFilter</filter-name>
  <url-pattern>/*</url-pattern>
 </filter-mapping>

　　filter代码如下：起到了过滤登陆界面login.jsp和根路径以外的过滤

 1 package com.FlyPig.util;
 2 
 3 import java.io.IOException;
 4 
 5 import javax.servlet.Filter;
 6 import javax.servlet.FilterChain;
 7 import javax.servlet.FilterConfig;
 8 import javax.servlet.ServletException;
 9 import javax.servlet.ServletRequest;
10 import javax.servlet.ServletResponse;
11 import javax.servlet.http.HttpServletRequest;
12 import javax.servlet.http.HttpServletResponse;
13 import javax.servlet.http.HttpSession;
14 
15 public class filter_session implements Filter {
16     private String encoding;
17 
18     public filter_session() {
19     }
20 
21     public void init(FilterConfig filterconfig) throws ServletException {
22         encoding = "utf-8";
23     }
24 
25     public void doFilter(ServletRequest servletrequest,
26             ServletResponse servletresponse, FilterChain filterchain)
27             throws IOException, ServletException {
28         servletrequest.setCharacterEncoding(encoding);
29         servletresponse.setCharacterEncoding(encoding);
30         HttpServletRequest req=(HttpServletRequest)servletrequest;
31         HttpSession session=req.getSession();
32         HttpServletResponse resp=(HttpServletResponse) servletresponse;
33         
34         String url=req.getRequestURI();
35         System.out.println(url);
36         if(!url.equals("/FlyPig")&&!url.equals("/FlyPig/login.jsp")){
37             if(session.getAttribute("username")==null||session.getAttribute("username")==""){
38                 resp.sendRedirect("login.jsp");
39                 return ;
40             }
41         }
42         
43         
44         filterchain.doFilter(servletrequest, servletresponse);
45     }
46 
47     public void destroy() {
48     }
49 }