samer@0: package samer.core;
samer@0: import  java.util.Hashtable;
samer@0: 
samer@0: /**
samer@0: 	The Registry stores Object class - Viewer class pairs.
samer@0: 	Associations can be added as Class objects or Class names (Strings).
samer@0: 	When creating a Viewer for a given object, matching is done on the
samer@0: 	basis that an exact Class matches is preferred, but failing that, parent
samer@0: 	Class matches are attempted up the Class heirarchy until a match is
samer@0: 	found.
samer@0: */
samer@0: 
samer@0: public class Registry
samer@0: {
samer@0: 	static { Shell.trace("initialising Registry"); }
samer@0: 	private static Hashtable map=new Hashtable();
samer@0: 
samer@0: 	/** register viewer as a Viewer class for objects of class obj */
samer@0: 	public static void put(Class obj, Class viewer) { map.put(obj.getName(),viewer); }
samer@0: 
samer@0: 	/** Registering by class name saves loading the class itself
samer@0: 		until it is actually needed. */
samer@0: 	public static void put(String obj, String viewer) { map.put(obj,viewer); }
samer@0: 
samer@0: 	/** Create and return a Viewer for the supplied object */
samer@0: 	public static Viewer createViewer(Object obj)
samer@0: 	{
samer@0: 		Class cl=obj.getClass();
samer@0: 
samer@0: 		// lookup by class NAME
samer@0: 		Object vwr=map.get(cl.getName());
samer@0: 		while (vwr==null) {
samer@0: 			cl=cl.getSuperclass();
samer@0: 			if (cl==null) return null;
samer@0: 			vwr=map.get(cl.getName());
samer@0: 		}
samer@0: 
samer@0: 		Class [] types = { cl };
samer@0: 		Object [] parms = { obj };
samer@0: 
samer@0: 		try {
samer@0: 			if (vwr instanceof String) vwr=Class.forName((String)vwr);
samer@0: 			return (Viewer)((Class)vwr).getConstructor(types).newInstance(parms);
samer@0: 		} catch (Exception ex) {
samer@0: 			Shell.trace(ex.toString());
samer@0: 			return null;
samer@0: 		}
samer@0: 	}
samer@0: }