I think getParameter is a method where in the you get the things from Url. No where you set the paramter values to get it,but in getAttribute you need to first set the attribute values using setAttribute method.
Newcomers to Web app development often get confused between attributes and parameters. Following are the two key differences between parameters and attributes: 1. Attributes are always set programmatically, while initialization parameters ( for example, servlet initialization and context initialization) are set declaratively in the DD file. 2. Also, there�s different in their APIs, for instance, the return type of parameters is String while that of Attributes is an Object.