code: public Object getParamKeyValue(HttpServletRequest request, ModelHandler modelHandler) {
  
  		Object keyValue = null;
  		try {
  			ModelMapping modelMapping = modelHandler.getModelMapping();
  			String keyName = modelMapping.getKeyName();
  			Debug.logVerbose("[JdonFramework] the keyName is  " + keyName, module);
  			String keyValueS = request.getParameter(keyName);
  			Debug.logVerbose("[JdonFramework] got the keyValue is  " + keyValueS, module);
  			if (keyValueS == null) {
  				Debug.logVerbose("[JdonFramework]the keyValue is null", module);
  			}
  			Class keyClassType = modelMapping.getKeyClassType();
  			if (keyClassType.isAssignableFrom(String.class)) {
  				keyValue = keyValueS;
  			} else {
  				Debug.logVerbose("[JdonFramework] convert String keyValue to" + keyClassType.getName(), module);
  				keyValue = ConvertUtils.convert(keyValueS, keyClassType);
  			}
  		} catch (Exception e) {
  			Debug.logError("[JdonFramework] getParamKeyValue error: " + e);
  		}
  		return keyValue;
  	}
docs: 获得参数key值 例如： /admin/productAction.do?action=edit&productId=1721
  缺省:productId为product的modelmapping.xml中key定义值
  
  对于如下调用： /admin/productAction.do?action=edit&userId=16
  userId不是modelmapping.xml中key定义值，则需要override本方法，
  
  
  @param actionMapping
  @param request
  @return 参数key值
  @throws java.lang.Exception