当会话超时时，重定向到GWT项目中的登录页面

Question

您能告诉我如何在GWT项目中捕获会话超时吗。我正在使用gwt调度库。我想知道我能不能做一些事情，比如实现一个过滤器，然后检查会话是否存在，但我想在gwt项目中有不同的方法。欢迎任何帮助。

感谢

Answer 1

客户端：所有回调都扩展了一个抽象回调，您可以在其中实现onFailur（）

public abstract class AbstrCallback<T> implements AsyncCallback<T> {
  @Override
  public void onFailure(Throwable caught) {
    //SessionData Expired Redirect
    if (caught.getMessage().equals("500 " + YourConfig.ERROR_MESSAGE_NOT_LOGGED_IN)) {
      Window.Location.assign(ConfigStatic.LOGIN_PAGE);
    }
    // else{}: Other Error, if you want you could log it on the client
  }
}

服务器：所有服务实现都扩展了AbstractServicesImpl，您可以在其中访问SessionData。重写onBeforeRequestDeserialized（StringserializedRequest）并检查那里的SessionData。如果SessionData已过期，则向客户端写入一条空间错误消息。此错误消息在您的AbstratrCallback中被选中并重定向到登录页面。

public abstract class AbstractServicesImpl extends RemoteServiceServlet {
  protected ServerSessionData sessionData;
  @Override
  protected void onBeforeRequestDeserialized(String serializedRequest) {
    sessionData = getYourSessionDataHere()
    if (this.sessionData == null){ 
      // Write error to the client, just copy paste
      this.getThreadLocalResponse().reset();
      ServletContext servletContext = this.getServletContext();
      HttpServletResponse response = this.getThreadLocalResponse();
      try {
        response.setContentType("text/plain");
        response.setStatus(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);
        try {
          response.getOutputStream().write(
            ConfigStatic.ERROR_MESSAGE_NOT_LOGGED_IN.getBytes("UTF-8"));
          response.flushBuffer();
        } catch (IllegalStateException e) {
          // Handle the (unexpected) case where getWriter() was previously used
          response.getWriter().write(YourConfig.ERROR_MESSAGE_NOT_LOGGED_IN);
          response.flushBuffer();
        }
      } catch (IOException ex) {
        servletContext.log(
          "respondWithUnexpectedFailure failed while sending the previous failure to the client",
          ex);
      }
      //Throw Exception to stop the execution of the Servlet
      throw new NullPointerException();
    }
  }
}

此外，您还可以重写doUnexpectedFailure（Throwablet）以避免记录抛出的NullPointerException。

@Override
protected void doUnexpectedFailure(Throwable t) {
  if (this.sessionData != null) {
    super.doUnexpectedFailure(t);
  }
}