EJB 3.1 Interceptors -- Same Transaction, Same Principal
Few days ago I’ve created a simple interceptors spike-solution at Github. Its purpose was to show my colleagues that in the EJB’s interceptors you can implement a code that exists in the same transaction and the same security context as the called EJB business method. Moreover, you can benefit from all the dependency injection you need.
This project uses the following resources injected by the Application Server:
TransactionSynchronizationRegistry– used for getting current transaction key and checking if we’re in the same transaction (I’ve written about it e.g. here),SessionContext– for reading user’s principal – user’s security context is also available in the interceptor,EntityManager– to persist some data before invoking the business method; it exists in the same transaction as the called method, so either both: the interceptor persistence and business method ends with success or both of them will be rolled-back.
This example also shows how easily you can add RESTful Web Service to your application (take a look at com.piotrnowicki.interceptors.web package).
It also shows that you can define interceptors in the deployment descriptor – without recompilation of your code. Such interceptors will be invoked for every business method in the given module (assuming no exclusion through annotation or DD occurs). An alternative is to define what beans or methods should be intercepted.