AJAX请求遭遇未登录和Session失效的解决方案

1.AJAX请求遭遇未登录和Session失效的解决方案

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;


/**
 * 登录过滤器
 *　　拥有Session是否失效和用户是否登录2个条件判断
 *　　如果是ajax请求则设置session超时
 * @author Merlin.Ma
 *
 */
 public class LoginFilter implements Filter{

private String redirectUrl = "/login.html";
private String sessionKey = "userName";

@Override
public void destroy() {
}

@Override
public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {
    
    HttpServletRequest req = (HttpServletRequest) request;
    HttpServletResponse rep = (HttpServletResponse) response;
    
    HttpSession session = req.getSession();
    
    if( session == null || session.getAttribute(sessionKey) == null){
        //如果判断是 AJAX 请求,直接设置为session超时
        if( req.getHeader("x-requested-with") != null && req.getHeader("x-requested-with").equals("XMLHttpRequest")  ) {
        
            rep.setHeader("sessionstatus", "timeout"); 
            
        } else {
            rep.sendRedirect( req.getContextPath() + redirectUrl);
        }
        
    }else {
        chain.doFilter(request, response);
    }      
}

@Override
public void init(FilterConfig filterConfig) throws ServletException {
    
    String url = filterConfig.getInitParameter("redirectUrl");
    String key = filterConfig.getInitParameter("sessionKey");
    
    redirectUrl = url == null? redirectUrl:url;
    sessionKey = key == null ? sessionKey : key ;
}


}

//全局的ajax访问，处理ajax清求时sesion超时 ，js代码直接贴到 配置config.js中，或者公共引入的js中

	$.ajaxSetup({
	    contentType : "application/x-www-form-urlencoded;charset=utf-8",
	    complete : function(XMLHttpRequest, textStatus) {
	        var sessionstatus = XMLHttpRequest.getResponseHeader("sessionstatus"); // 通过XMLHttpRequest取得响应头，sessionstatus，
	        if (sessionstatus == "timeout") {
	            // 如果超时就处理 ，指定要跳转的页面
	            window.location.replace("login.html");
	        }
	    }
	});