过滤器（当前登录人的信息（session过期时）进行重新登录）

第一步：书写过滤器类，过滤器必须继承org.springframework.web.servlet.handler.HandlerInterceptorAdapter并重写preHandle方法。

/**
* 检测是否已经登录
* <p>Title:SecurityInterceptor </p>
* <p>Description: </p>
* @author zhanghaodong
* @date 2015年11月27日 上午11:18:56
*/
public class SecurityInterceptor extends HandlerInterceptorAdapter {

        @Override 
        public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { 
            if((request.getContextPath().replace("/", "")).equals((request.getRequestURI().replace("/", "")))){
                return true;
            }
            HttpSession session = request.getSession(true); 
            // 从session 里面获取用户名的信息 
            Object obj =session.getAttribute(WebCnts.SESSION_KEY_LOGINUSER);
            // 判断如果没有取到用户信息，就跳转到登陆页面，提示用户进行登陆 
            if (obj == null || "".equals(obj.toString())) { 
                  response.setContentType("text/html"); 
                    response.setCharacterEncoding("utf-8"); 
                    PrintWriter out = response.getWriter();   
                    StringBuilder builder = new StringBuilder();   
                    builder.append("<script type=\"text/javascript\" charset=\"UTF-8\">");   
                    builder.append("alert(\"登录已过时,请重新登陆！\");");   
                    builder.append("parent.window.location.href='"+request.getContextPath()+"/login';");    
                    builder.append("</script>");   
                    out.print(builder.toString());   
                    out.close();   
                    return false; 
            } 
            return true; 
        } 

        @Override 
        public void postHandle(HttpServletRequest req, HttpServletResponse res, Object arg2, ModelAndView arg3) throws Exception { 
        } 

        @Override 
        public void afterCompletion(HttpServletRequest req, HttpServletResponse res, Object arg2, Exception arg3) throws Exception { 
        } 

}



第二步：在spring-mvc.xml文件中添加下面代码（过滤的路径）

    <mvc:interceptors>
        <mvc:interceptor>
           <!--过滤所有的路径  -->
            <mvc:mapping path="/**"/>
     <!--去掉不需要进行过滤的路径，如：静态的路径  -->
            <mvc:exclude-mapping path="/login"/> 
            <mvc:exclude-mapping path="/plugins/**"/> 
            <mvc:exclude-mapping path="/public/**"/> 
            <mvc:exclude-mapping path="/upload/**"/> 
            <mvc:exclude-mapping path="/getCaptha"/> 
            <mvc:exclude-mapping path="/demo/*.json"/> 
            <bean class="com.hiersun.ecommerce.security.SecurityInterceptor"/>
        </mvc:interceptor>
    </mvc:interceptors>