code: public ThymeleafEngineConfigBuilder<P> setMessageResolver(final IMessageResolver messageResolver) {
  		messageResolvers().clear();
  		messageResolvers().add(messageResolver);
  		return this;
  	}
docs: <p>
  Sets a single message resolver for this template engine.
  </p>
  <p>
  Calling this method is equivalent to calling
  {@link #setMessageResolvers(Set)} passing a Set with only one message
  resolver.
  </p>
  <p>
  This operation can only be executed before processing templates for the
  first time. Once a template is processed, the template engine is
  considered to be <i>initialized</i>, and from then on any attempt to
  change its configuration will result in an exception.
  </p>
  
  @param messageResolver
  the message resolver to be set.
  @return this for fluent use