When session timeout redirect to login page in GWT project

Could you advice me how to proceed in catching session timeout in a GWT project. I m using gwt dispatch lib. I m wonderig can i do something like implementing a filter and then checking if session exist or no but i suppose in gwt projects there are different approaches. Any help is welcome.



Client: All Callbacks extend a Abstract Callback where you implement the onFailur()

public abstract class AbstrCallback<T> implements AsyncCallback<T> {

  public void onFailure(Throwable caught) {
    //SessionData Expired Redirect
    if (caught.getMessage().equals("500 " + YourConfig.ERROR_MESSAGE_NOT_LOGGED_IN)) {
    // else{}: Other Error, if you want you could log it on the client

Server: All your ServiceImplementations extend AbstractServicesImpl where you have access to your SessionData. Override onBeforeRequestDeserialized(String serializedRequest) and check the SessionData there. If the SessionData has expire then write a spacific error message to the client. This error message is getting checkt in your AbstrCallback and redirect to the Login Page.

public abstract class AbstractServicesImpl extends RemoteServiceServlet {

  protected ServerSessionData sessionData;

  protected void onBeforeRequestDeserialized(String serializedRequest) {

    sessionData = getYourSessionDataHere()

    if (this.sessionData == null){ 
      // Write error to the client, just copy paste
      ServletContext servletContext = this.getServletContext();
      HttpServletResponse response = this.getThreadLocalResponse();
      try {
        try {
        } catch (IllegalStateException e) {
          // Handle the (unexpected) case where getWriter() was previously used
      } catch (IOException ex) {
          "respondWithUnexpectedFailure failed while sending the previous failure to the client",
      //Throw Exception to stop the execution of the Servlet
      throw new NullPointerException();


In Addition you can also Override doUnexpectedFailure(Throwable t) to avoid logging the thrown NullPointerException.

protected void doUnexpectedFailure(Throwable t) {
  if (this.sessionData != null) {

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