Getting started with persistence

Using Guice-Persist

<dependency>
    <groupId>com.guicedee.services</groupId>
    <artifactId>guice-persist</artifactId>
</dependency>

To enable persistence support, simply install the JPA module in the IGuiceModule SPI. This method is restricted to JPA, and multiple jpa bindings require private modules.

module my.module{
    provides IGuiceModule with MyJpaPersistModule;
}

public class MyJpaPersistModule extends JpaPersistModule
{
    public MyJpaPersistModule()
    {
        super("myFirstJpaUnit");
    }
}

Finally, you must decide when the persistence service is to be started by invoking start() on PersistService. I typically use a simple initializer class that I can trigger at a time of my choosing:

public class MyInitializer {
@Inject MyInitializer(PersistService service) {
    service.start();
    // At this point JPA is started and ready.
    }
}

By default, any method marked with @Transactional will have a transaction started before, and committed after it is called.

@Transactional
@Transactional(rollbackOn = { IOException.class, RuntimeException.class, ... })
@Transactional(rollbackOn = IOException.class, ignore = FileNotFoundException.class)
public void myMethod() { ... }
        

A unit of work is roughly the lifespan of an EntityManager (in JPA). It is the session referred to in the session-per-* strategies.

public class MyBackgroundWorker {
    @Inject private UnitOfWork unitOfWork;
    public void doSomeWork() {
        unitOfWork.begin();
        try {
        // Do transactions, queries, etc...
        //...
        } finally {
        unitOfWork.end();
        }
    }
}