Ajax请求session失效该如何解决

一般来说我们的项目都有登录过滤器，一般请求足以搞定。但是AJAX却是例外的，所以解决方法是设置响应为session失效。

一共分为过滤器和页面JS两个部分的设置，先看过滤器的修改：

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;

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 ;
  }
}

代码简单，就不过多进行注释了，现在看JS部分的代码。当然是基于jQuery的~~

//全局的ajax访问，处理ajax清求时sesion超时 
$.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");
    }
  }
});

页面加载这段js代码，然后开始调用ajax。在不登陆或者session失效的情况下，可以看到页面跳转到登录页面。