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

package com.FlyPig.util;

import java.io.IOException;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class filter_session implements Filter {
    private String encoding;

    public filter_session() {
    }

    public void init(FilterConfig filterconfig) throws ServletException {
        encoding = "utf-8";
    }

    public void doFilter(ServletRequest servletrequest,
            ServletResponse servletresponse, FilterChain filterchain)
            throws IOException, ServletException {
        servletrequest.setCharacterEncoding(encoding);
        servletresponse.setCharacterEncoding(encoding);
        HttpServletRequest req=(HttpServletRequest)servletrequest;
        HttpSession session=req.getSession();
        HttpServletResponse resp=(HttpServletResponse) servletresponse;
        
        String url=req.getRequestURI();
        System.out.println(url);
        if(!url.equals("/FlyPig")&&!url.equals("/FlyPig/login.jsp")){
            if(session.getAttribute("username")==null||session.getAttribute("username")==""){
                resp.sendRedirect("login.jsp");
                return ;
            }
        }
        
        
        filterchain.doFilter(servletrequest, servletresponse);
    }

    public void destroy() {
    }
}