Factory-method and constructors with arguments

[azack]

Hi, I've noticed a behavior that seems counter-intuitive to me and am wondering if I have made a bad assumption and if this is the way it is supposed to work.

I believe that if I use factory-method, Spring AS should call the method specified and not the constructor of the class. This seems to be true unless the constructor takes an argument; if it does, then Spring AS calls the constructor, then the method specified by factory-method.

Consider this example. I have the following object in my application context XML:

	<object id="mySingleton" class="single.MySingleton" factory-method="getInstance">
	</object>

If MySingleton is this:

package single {
	public class MySingleton {
		private static var _instance : MySingleton;
		
		public function MySingleton() {
			trace('Constructor');
		}
		
		public static function getInstance() : MySingleton {
			trace('getInstance()');
			if (_instance == null) {
				_instance = new MySingleton();
			}
			return _instance;
		}
	}
}

Then it works as I expected; Spring AS calls my getInstance method, which internally calls my constructor. In the debugger I see:

Fri Oct 23 17:39:17 GMT-0400 2009 INFO - org.springextensions.actionscript.ioc.factory.supp ort.DefaultListableObjectFactory - Pre-instantiating singletons in [object FlexXMLApplicationContext]
getInstance()
Constructor

If, however, MySingleton is this:

package single {
	public class MySingleton {
		private static var _instance : MySingleton;
		
		public function MySingleton( value : String ) {
			trace('Constructor: ' + value);
		}
		
		public static function getInstance() : MySingleton {
			trace('getInstance()');
			if (_instance == null) {
				_instance = new MySingleton("foo");
			}
			return _instance;
		}
	}
}

I see this:

Fri Oct 23 17:38:33 GMT-0400 2009 INFO - org.springextensions.actionscript.ioc.factory.supp ort.DefaultListableObjectFactory - Pre-instantiating singletons in [object FlexXMLApplicationContext]
Constructor: null
getInstance()
Constructor: foo

Obviously if the value passed to the constructor is used in a nontrivial way, bad things can happen (null reference or other runtime error).

Can someone please help me understand what's happening here? Thanks.

[666shooter]

this is very probably related to this:

http://www.springactionscript.org/faq.html#trace-errors

Its a workaround for a flashplayer bug in the reflection API, it needs to call the constructor without constructor arguments once, to be able to retrieve the information about the constructor arguments.
This is a very unfortunate side-effect that right now we can't do anything about.

cheers,

Roland

[azack]

Alright, I understand the underlying problem with Flash that requires the constructor to be called in order to figure out its arguments.

However, what I don't understand now is why should the framework want to even do that when there is a factory-method specified. Is it to support autowiring of the constructor arguments?