Ajax 请求session过期的统一处理

public class LoginInterceptor extends HandlerInterceptorAdapter {

	@SuppressWarnings("unused")
	private static final Logger log = Logger.getLogger(LoginInterceptor.class);
	
	@Override
	public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
			throws Exception { 
//		log.info("URL="+request.getRequestURL().toString());
		Object obj = request.getSession().getAttribute(SecurityConstants.LOGIN_USER);
		if (null == obj) {  
        	if (WebUtil.isAjaxRequest(request)){ 
	            response.setHeader("sessionstatus", "timeout");  
	        }else{
	        	response.sendRedirect(request.getContextPath()+"/usr/login");
	        }  
        	return false;
        }  
		return super.preHandle(request, response, handler);
	}
}

public static boolean isAjaxRequest(HttpServletRequest request){ 
		boolean result = false;
		
	　　　　 String headerX = request.getHeader("X-Requested-With");			
	        return headerX != null  && headerX.equalsIgnoreCase("XMLHttpRequest");			
		
	}

/**
 * 设置未来(全局)的AJAX请求默认选项
 * 主要设置了AJAX请求遇到Session过期的情况
 */
$.ajaxSetup({
    type: 'POST',
    complete: function(xhr,status) {
        var sessionStatus = xhr.getResponseHeader('sessionstatus');
        if(sessionStatus == 'timeout') {
            var top = getTopWinow();
            var yes = confirm('由于您长时间没有操作, session已过期, 请重新登录.');
            if (yes) {
                top.location.href = '/skynk/index.html';            
            }
        }
    }
});

/**
 * 在页面中任何嵌套层次的窗口中获取顶层窗口
 * @return 当前页面的顶层窗口对象
 */
function getTopWinow(){
    var p = window;
    while(p != p.parent){
        p = p.parent;
    }
    return p;
}