userloginfilter.java

一个简单的同学录

package txl.filter;

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

public class UserLoginFilter implements Filter {
	 protected FilterConfig filterConfig;
	    
	    /**
	     *初始化过滤器,和一般的Servlet一样，它也可以获得初始参数。
	     */
	    public void init(FilterConfig config) throws ServletException {
	        this.filterConfig = config;
	    }
	    
	    /**
	      *进行过滤处理，这个方法最重要，所有过滤处理的代码都在此实现。
	      */
	     public  void doFilter(ServletRequest request, ServletResponse  response, FilterChain chain)
	        throws IOException, ServletException {
	    	 HttpServletRequest hreq = (HttpServletRequest)request;
	         HttpServletResponse hres = (HttpServletResponse)response;
	         HttpSession session = hreq.getSession();
	         String isLogin="";
	         try
	         {
	         	isLogin=(String)session.getAttribute("userLogin");        
	             if(isLogin==null){
	            	 hres.sendRedirect("/txl/userlogin/login.jsp");
	             }else if(isLogin.equals("true")){
	            	 chain.doFilter(hreq,hres);
	             }else{
	            	 hres.sendRedirect("/txl/userlogin/login.jsp");
	             }
			 }
	         catch(Exception e)
	         {         
	         	e.printStackTrace();
	         }
			 	
	    }   

		public void setFilterConfig(final FilterConfig filterConfig)
		{
			this.filterConfig=filterConfig;
		}
	    
	    //销毁过滤器
		public void destroy()
		{
			this.filterConfig=null;
		}
}