Using Annotations to Check Structural Properties of Classes

The specification of meta-information, by using attributes in .NET or annotations in Java, along with the source code is gaining widespread use. Meta-information is used for different purposes such as code generation or configuration of the environment in which a class is deployed. However, in most cases using an annotation also implies that constraints, beyond those defined by the language's semantics, have to be followed. E.g., a class must define a no-arguments constructor or the parameters of a method must have specific types. Currently, these constraints are not checked at all or only to a very limited extend. Hence, a violation can remain undetected and result in deployment-time or even subtle run-time errors. In this paper, we present a user-extensible framework that enables the definition of constraints to check the properties of annotated elements. Further, we demonstrate the application of the framework to check the constraints defined in the EJB 3.0 specification, and an evaluation of the approach based on checking the xPetstore-EJB3.0 project from within Eclipse to test the performance.