Getting com.google.gwt.user.client.rpc.StatusCodeException: 0 in GWT

Question

I sometimes/often get this Exception in GWT but don't know why:

SEVERE: com.google.gwt.user.client.rpc.StatusCodeException: 0 
java.lang.RuntimeException: com.google.gwt.user.client.rpc.StatusCodeException: 0 
    at Unknown.java_lang_RuntimeException_RuntimeException__Ljava_lang_Throwable_2V(Unknown Source)
    at Unknown.de_ctech24_simplynews_web_client_util_SimpleCallback_$onFailure__Lde_ctech24_simplynews_web_client_util_SimpleCallback_2Ljava_lang_Throwable_2V(Unknown Source)
    at Unknown.com_google_gwt_user_client_rpc_impl_RequestCallbackAdapter_$onResponseReceived__Lcom_google_gwt_user_client_rpc_impl_RequestCallbackAdapter_2Lcom_google_gwt_http_client_Request_2Lcom_google_gwt_http_client_Response_2V(Unknown Source)
    at Unknown.com_google_gwt_http_client_Request_$fireOnResponseReceived__Lcom_google_gwt_http_client_Request_2Lcom_google_gwt_http_client_RequestCallback_2V(Unknown Source)
    at Unknown.com_google_gwt_http_client_RequestBuilder$1_onReadyStateChange__Lcom_google_gwt_xhr_client_XMLHttpRequest_2V(Unknown Source)
    at Unknown.<anonymous>(Unknown Source)
    at Unknown.com_google_gwt_core_client_impl_Impl_apply__Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_Object_2(Unknown Source)
Caused by: com.google.gwt.user.client.rpc.StatusCodeException: 0 
    at Unknown.java_lang_RuntimeException_RuntimeException__Ljava_lang_String_2Ljava_lang_Throwable_2V(Unknown Source)
    at Unknown.com_google_gwt_user_client_rpc_StatusCodeException_StatusCodeException__ILjava_lang_String_2V(Unknown Source)
    at Unknown.com_google_gwt_user_client_rpc_impl_RequestCallbackAdapter_$onResponseReceived__Lcom_google_gwt_user_client_rpc_impl_RequestCallbackAdapter_2Lcom_google_gwt_http_client_Request_2Lcom_google_gwt_http_client_Response_2V(Unknown Source)
    at Unknown.com_google_gwt_http_client_Request_$fireOnResponseReceived__Lcom_google_gwt_http_client_Request_2Lcom_google_gwt_http_client_RequestCallback_2V(Unknown Source)
    at Unknown.com_google_gwt_http_client_RequestBuilder$1_onReadyStateChange__Lcom_google_gwt_xhr_client_XMLHttpRequest_2V(Unknown Source)
    at Unknown.<anonymous>(Unknown Source)
    at Unknown.com_google_gwt_core_client_impl_Impl_apply__Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_Object_2Ljava_lang_Object_2(Unknown Source)

After spending some time Googling i found this: http://www.mail-archive.com/[email protected]/msg79537.html

There an interesting hint was given: it occured if you disconnect your WLAN and connect again - then the error arises. I tried this on my notebook - then the exception occurs.

Another problem is this exception arises sometimes (not really always at the same time or when executing a specific action - so seemingly random) although the network connection is fine. I don't know why this happens nor what's the correct way to handle it - sure I can catch and ignore it. But the request never goes to the server and the action is not executed - not quite a good error handling.

Some data about this app - maybe this helps narrowing or hopefully solving the problem:

• GWT 2.4 with Sencha GXT 3.0.1
• Occurs on all the top browsers in newest version: IE, Chrome, Firefox
• Using Cloudflare (I also tried without it - but it's the same problem. So this seems not to be originated by using this Proxy-Service.)

Thanks a lot for every hint and every idea how to handle/solve this.

Answer 1

Since there is no HTTP status code 0, this appears not to be from the server - it could be worthwhile to test using Firebug or something, just to make sure that there isn't a bad response like this coming back.

Instead, this is almost certainly from the browser itself, either the connection timed out or was dropped by the server, or the browser couldn't reach the server (bad dns, bad gateway, lost wifi, server not available).

Treat this like any unexpected server failure - perhaps back off and try again, display a message to the user, log an error and send that when the connections are working again.

The fact that it is happening in all browsers points to a network or server issue - it is extremely unlikely that all browsers are failing in unpredictable ways together. This fact also makes it easier to debug - you can use your favorite browser's debug tools.