StrutsCatalog: Check Actions for preconditions

The  execute  method in the Action is a key hotspot in the framework, and may be realizing several different API contracts. To be sure all the contracts are being met, provide a general error catching routine for your Actions. This method can look for any number of preconditions, such as whether there is a form bean for the expected subclass. If these preconditions fail, in most cases a runtime exception should be thrown. A broken contract is usually a programming error that needs to be fixed without delay. The Action should expose the error so that it can be quickly corrected.

{ { { A common case is checking for a null form bean. If an Action expects an ActionForm bean, then its API contract with the ActionMappings should require that a particular ActionForm bean, or subclass thereof, be named in the ActionMapping. The Action's contract with the controller is that it will always instantiate the bean before the Action is called. If either contract is broken, the application should expose a null pointer exception, or other runtime exception, so that the programming error is fixed and the misunderstanding resolved. Whether an Action expects an ActionForm bean should be specified in its Javadoc. } } }



StrutsCatalogPreconditions (last edited 2009-09-20 23:11:51 by localhost)