Decouple validation processes from your business object implementations
Version 1.3 of the Java platform saw the introduction of the dynamic proxy facility. Dynamic proxies offer many interesting solutions to Java developers, including a validation scheme that easily decouples validation logic from an application’s core business logic. In this article, Java developer Eric Olson shows you how dynamic proxies can keep your core application code free of validation routines and focused solely on business logic.
Validation is an essential aspect of many enterprise applications. Most business methods contain validation logic to ensure that pre-conditions are met before carrying out business logic. Code that deals with values entered through a user interface employs validation logic to ensure that the values entered by a user are valid before carrying out actions that may affect other areas of the application or other users. Validation is an especially important component of applications that employ and interact with other loosely coupled components, as well as services that may not be strict in their assertions.
As important as it is to the safety and functionality of your business applications, core application logic is often cluttered with validation routines. Validation processes are often scattered throughout method calls, making it difficult to tell the difference between validation logic and core business logic. In most cases, business objects and methods must know some details of the validation process and deal with them directly in their implementation — for example, a business object may throw a validation exception directly from the business method (either coded directly in the method, or as a result of calling some validation service). The validation exception in this case is really a byproduct of the validation process, however, and would ideally be hidden from the business object implementation.
In this article, I’ll show you a more decoupled and centralized approach to validation, using the dynamic proxy facility introduced to the Java platform with version 1.3. Working with a single example throughout the article, I’ll demonstrate the weaknesses of both tightly coupled and loosely coupled validation schemes, and then show you how dynamic
