DI

Despite the fact that EJB inheritance sometimes uses Java inheritance – they’re not always the same. Just as you could read in my previous post, EJB doesn’t have to implement any interface to expose a business interface. The other way around is also true – just because EJB is implementing some interface or extending other EJB doesn’t mean it exposes all or any of its views. Let’s say we want to have some basic EJB exposing remote business interface. We then want to extend this EJB and override remote business methods. Nothing fancy, right? But let’s take a look at some examples. ...

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). ...

You probably know that if you use BMT (Bean Managed Transactions) you can get information about current transaction status by using UserTransaction interface (which implementation can be fetched either by JNDI or using dependency injection) and executing it’s getStatus() method. If you use CMT (Container Managed Transactions) you cannot use UserTransaction interface. Instead, you can manage your transaction through SessionContext interface. This interface gives you two places that hooks to the current transaction: setRollbackOnly(-) and getRollbackOnly(). But what if you would like to check the current transaction’s status? ...