code: public ModelHandler borrowHandlerObject(String formName) {
  		ModelHandler modelHandler = null;
  		try {
  			modelHandler = makeHandlerObject(formName);
  		} catch (Exception e) {
  			Debug.logError("[JdonFramework]borrowHandlerObject error:" + e, module);
  		}
  		/**
  		 * ModelHandler modelHandler = null; try { String poolKey =
  		 * (modelHandlerClassBuilder.getModelMapping(formName)).getHandler();
  		 * 
  		 * LinkedList listFree = (LinkedList) handlerFreePool.get(poolKey); if
  		 * ((listFree == null) || (listFree.isEmpty())) { // 如果空了，生产 listFree =
  		 * makeHandlerObjects(formName); handlerFreePool.put(poolKey, listFree);
  		 * } modelHandler = (ModelHandler) listFree.removeFirst();
  		 * 
  		 * // 加入已经用的池 LinkedList listUsed = (LinkedList)
  		 * handlerUsedPool.get(poolKey); if (listUsed == null) { listUsed = new
  		 * LinkedList(); handlerUsedPool.put(poolKey, listUsed); }
  		 * listUsed.add(modelHandler);
  		 * 
  		 * Debug.logVerbose("[JdonFramework]--> borrow Modelhandler instance " +
  		 * poolKey + listFree.size() + " for " + formName, module); } catch
  		 * (Exception e) {
  		 * Debug.logError("[JdonFramework]borrowHandlerObject error:" + e,
  		 * module); }
  		 **/
  		return modelHandler;
  	}
docs: 获得一个空闲的ModelHandler 如果空闲池没有，就重新生成指定个数的ModelHandler实例。 获得成功，则记入在用池。
  当客户端调用完毕，调用returnHandlerObject返回该ModelHandler实例备重用。
  
  @param formName
  @return
  @throws java.lang.Exception