1. Eclipse中的Command模式，使得具體的實現和Command定義分離，便於維護。

但是在Debug的時候，或者沒有souce code的時候，我們想知道每一個commandId對應的Handler是什麼，怎麼辦？

2. 在Eclipse 4.x中，其實當Eclipse啟動完成後，它已經建立了commandId和對應Handler的Map，儲存在EclipseContext中，

然後通過反射呼叫到對應的Handler。 見下圖：

Eclipse是在上圖中我框出來的地方，通過commandId在EclipseContext中查詢到。

3. 如何將EclipseContext中的Handler都dump出來呢？

一句話，反射。

注意，以下程式碼我只在Eclipse 4.3.0上測試通過。

		//try to print all handler in eclipse 4.x
		result = ReflectionUtils.getField("e4Context", site);
		if(!isSuccess(result)) {
			return;
		}
		
		if(result instanceof IEclipseContext) {
			IEclipseContext context = (IEclipseContext)result;
			printHandlerForEclipseContext(context, 0);
		}

 

	@SuppressWarnings("unchecked")
	private void printHandlerForEclipseContext(IEclipseContext context, int step) {
		Assert.isNotNull(context);
		
		Object result = null;
		if(step != 0) {
			result = ReflectionUtils.getField("localValueComputations", context);
		} else {
			result = ReflectionUtils.getField("localValues", context);
		}
		if(!isSuccess(result)) {
			return;
		}
		
		if(result instanceof Map) {
			String stepString = makeStep(step);
			Map<String, Object> localValueComputations = (Map<String, Object>)result;
			for (String string : localValueComputations.keySet()) {
				Object object = localValueComputations.get(string);
				
				String last = object.toString();
				if(string.startsWith("legacy::handler::")) {
					if(object instanceof ArrayList) {
						ArrayList list = (ArrayList)object;
						//TODO may be more than one item in list
						object = list.get(0);
						if(object instanceof IHandlerActivation) {
							IHandlerActivation activation = (IHandlerActivation)object;
							last = activation.getHandler().toString();
						}
					}
				}
				System.out.println(stepString + string + ", " + last);
			}
		}
		result = null;
		
		result = ReflectionUtils.invokeMethod(context, "getChildren");
		if(!isSuccess(result)) {
			return;
		}
		
		if(result instanceof Set) {
			Set<IEclipseContext> children = (Set<IEclipseContext>)result;
			Iterator<IEclipseContext> iterator = children.iterator();
			IEclipseContext child = null;
			int moreStep = step + 1;
			while(iterator.hasNext()) {
				child = iterator.next();
				printHandlerForEclipseContext(child, moreStep);
			}
			step ++;
		}
	}
 

...

legacy::handler::org.eclipse.ui.edit.text.recenter, ActionHandler([email protected])
legacy::handler::org.eclipse.jdt.ui.edit.text.java.search.declarations.in.hierarchy, ActionHandler([email protected]26e4a)
legacy::handler::org.eclipse.jdt.ui.edit.text.java.search.declarations.in.project, ActionHandler([email protected]3f5)
legacy::handler::org.eclipse.jdt.ui.edit.text.java.surround.with.try.multicatch, ActionHandler([email protected]996)
legacy::handler::org.eclipse.jdt.ui.edit.text.java.override.methods, ActionHandler([email protected])
legacy::handler::org.eclipse.ui.edit.findPrevious, ActionHandler(org.eclipse.ui.texteditor.FindNextAction@69d5ee81)
handler::org.eclipse.jdt.ui.edit.text.java.remove.block.comment, org.eclipse.ui.[email protected]207462c0

...