package com.atlassian.johnson.spring.lifecycle;
   
   import com.atlassian.johnson.spring.web.context.support.JohnsonHttpRequestHandlerServlet;
   
   import javax.annotation.Nonnull;
   import javax.servlet.ServletException;
   import javax.servlet.http.HttpServletRequest;
   import javax.servlet.http.HttpServletResponse;
   import java.io.IOException;
  
  /**
   * A specialized {@link JohnsonHttpRequestHandlerServlet} for use with the {@link LifecycleDispatcherServlet}. This
   * servlet automatically redirects to the error page when requests are received during application startup.
   *
   * @since 3.0
   */
  public class LifecycleHttpRequestHandlerServlet extends JohnsonHttpRequestHandlerServlet {
  
      private volatile boolean starting = true;
  
      @Override
      public void init() throws ServletException {
          LifecycleState state = LifecycleUtils.getCurrentState(getServletContext());
          if (state == LifecycleState.STARTED) {
              starting = false;
  
              super.init();
          }
      }
  
      @Override
      protected void service(@Nonnull HttpServletRequest request, @Nonnull HttpServletResponse response)
              throws ServletException, IOException {
          if (starting) {
              if (LifecycleUtils.isStarting(getServletContext())) {
                  //Otherwise, if the application is still starting, redirect the request to the error page
                  sendRedirect(response);
  
                  return;
              } else {
                  //The first time we see a status other than CREATED or STARTING, note that the application
                  //is no longer starting and service the request normally
                  starting = false;
              }
          }
  
          super.service(request, response);
      }
  }