code: protected final ServletContextInitializer[] mergeInitializers(
  			ServletContextInitializer... initializers) {
  		List<ServletContextInitializer> mergedInitializers = new ArrayList<>();
  		mergedInitializers.add((servletContext) -> this.initParameters
  				.forEach(servletContext::setInitParameter));
  		mergedInitializers.add(new SessionConfiguringInitializer(this.session));
  		mergedInitializers.addAll(Arrays.asList(initializers));
  		mergedInitializers.addAll(this.initializers);
  		return mergedInitializers.toArray(new ServletContextInitializer[0]);
  	}
docs: Utility method that can be used by subclasses wishing to combine the specified
  {@link ServletContextInitializer} parameters with those defined in this instance.
  @param initializers the initializers to merge
  @return a complete set of merged initializers (with the specified parameters
  appearing first)