Bean Validation

Abstract

The previous chapter talked about Context and Dependency Injection which has become a central and common specification across Java EE. It solves recurrent problems (injection, alternatives, stereotypes, producers . . .) that developers have in their day-to-day job. Validating data is also a common task that is spread across several, if not all, layers of today's applications (from presentation to database). Because processing, storing, and retrieving valid data are crucial for an application, each layer defines validation rules its own way. Often the same validation logic is implemented in each layer, proving to be time-consuming, harder to maintain, and error prone. To avoid duplication of these validations in each layer, developers often bundle validation logic directly into the domain model, cluttering domain classes with validation code that is, in fact, metadata about the class itself.