composer - getData beforeCompose

<script type="text/JavaScript">
 				 <![CDATA[
 				function init() {
 				var data = '${mapView$composer.data}'.evalJSON();
 				for (var key in data) {
						if (data.hasOwnProperty(key)) {
							alert(key);
						  }
					}
 				}
  				]]>
			</script>

//this work fine if i hardcode the objects
public JSONArray getData(){
		JSONArray a = new JSONArray();
		a.push("m3");
                a.push("m4");
		return a;
	}

MyWindow container = (MyWindow) comp.getParent();

public JSONArray getData(){
//this won't work because javascript calls the method before the page is composed, therefore container = null;
		JSONArray a = new JSONArray();
		List<String> list = new ArrayList<String>();
		list = container.getList();
		
		for(String str : list){
			a.push(str);
		}
		return a;
	}