servlet过滤器过滤所有，只放行登录相关模块

最近做项目用到了servlet的过滤器，发现如果仅仅只是从web.xml文件上配置不够灵活，很难达到项目要求，用户体验度也不好，故在配置文件中加上过滤应用全局：

 <filter>
	<filter-name>Limit</filter-name>
	<filter-class>com.spditir.filter.LimitFilter</filter-class>
	</filter>
<filter-mapping>
	<filter-name>Limit</filter-name>
	<url-pattern>/*</url-pattern>
	</filter-mapping>

只放行和登录模块相关的资源，如下：

package com.speed.filter;

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;

/*
 * 安全过滤器修正v1版本
 * 功能：只允许登录过的用户访问资源
 */
public class LimitFilter implements Filter {

	FilterConfig filterconfig;

	public void init(FilterConfig arg0) throws ServletException {
		filterconfig = arg0;
	}

	public void doFilter(ServletRequest arg0, ServletResponse arg1,
			FilterChain arg2) throws IOException, ServletException {
		HttpServletRequest request = (HttpServletRequest) arg0;
		HttpServletResponse response = (HttpServletResponse) arg1;
		String   request_uri   =   request.getRequestURI(); 		
		String   ctx_path   =   request.getContextPath(); 
		
		
		if(request_uri.substring(ctx_path.length()).equals("/loginFailure.jsp")
				|| request_uri.substring(ctx_path.length()).equals("/")
				|| request_uri.substring(ctx_path.length()).equals("/validateCode.action")
				|| request_uri.substring(ctx_path.length()).equals("/loginByForm.jsp")				
				|| request_uri.substring(ctx_path.length()).equals("/userMgr.action"))   
		{	
			System.out.println("------filter输出------安全验证登录通过uri："+request_uri);
                           	arg2.doFilter(arg0, arg1);
		}else if(request_uri.substring(ctx_path.length()).equals("/images/login2.jpg")
				||request_uri.substring(ctx_path.length()).equals("/images/enter.gif")
				||request_uri.substring(ctx_path.length()).equals("/images/reset.gif")
				||request_uri.substring(ctx_path.length()).equals("/images/shutdown.jpg")){
			arg2.doFilter(arg0, arg1);
		}else{
			if (request.getSession().getAttribute("USER_INFO") == null) {
				response.setCharacterEncoding("utf-8");
				System.out.println(ctx_path+"/loginFailure.jsp");
				response.sendRedirect(ctx_path+"/loginFailure.jsp");
				return;
			} else {
				arg2.doFilter(arg0, arg1);
			}
		}
				
	}

	public void destroy() {     
	}
}