产生原因：设置了2次跨域，但只能有一个。

说明nginx和后台服务（java）重复设置了。

先检查nginx

server{
        listen       80;
        server_name  dev.test.com;
        location / {

              if ( $http_origin ~ http://(.*).test.com){
                   set $allow_url $http_origin;
              }

              add_header 'Access-Control-Allow-Origin' $allow_url;
              add_header 'Access-Control-Allow-Methods' 'GET,POST,OPTIONS' always;
              add_header 'Access-Control-Allow-Credentials' 'true' always;
              add_header 'Access-Control-Allow-Headers' 'Accept,Authorization,Cache-Control,Content-Type,Access-Token,token,DNT,If-Modified-Since,Keep-Alive,Origin
,User-Agent,X-Requested-With' always;
              add_header 'Access-Control-Expose-Headers' 'WD-Total-Length,WD-Phone-Modal,WD-Client-Id,WD-Udid,WD-Need-More';

              if ($request_method = OPTIONS){
                     return 204;
              }
              proxy_pass http://127.0.0.1:10001/;
        }

        error_page 404 /404.html;
            location = /40x.html {
        }

        error_page 500 502 503 504 /50x.html;
            location = /50x.html {
        }
    }

在检查后台服务

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
        response.setHeader("Access-Control-Allow-Origin", "*");
        response.setHeader("Access-Control-Allow-Methods", "POST, GET, OPTIONS");
        response.setHeader("Access-Control-Max-Age", "3600");
        response.setHeader("Access-Control-Allow-Headers", "x-requested-with");
        response.setHeader("Access-Control-Allow-Credentials","true");
        return super.preHandle(request, response, handler);
    }

确实重复设置了，后台去掉就可以了，一般90%的问题就能解决掉。

如果还是失败的话，看有没有使用  @CrossOrigin 注解，去掉就可以了。

如果还是失败，可以留言，相互学习。