CDI Injection and serialization

Question

I'm considering to use CDI injection for slf4j logger, so I've created a producer.

I'm injecting it into an ApplicationScoped bean which is serializable:

@ApplicationScoped
public final class CurrentApplicationBean implements Serializable {
    @Inject
    private transient Logger          logger;
}

It must be transient because org.slf4j.Logger is an interface which doesn't extend Serializable, but this means that the logger must be re-injected after deserialization.

I think that CDI doesn't handle that, what's you knowledge?

Moreover, the provider always provides a new Logger instance beacuse it must set the logger name from the InjectionPoint, this means that RequestScoped beans have their own logger instance instead of a static per class logger.

Maybe logging is not a good context for CDI injection... what are your considerations?

While org.slf4j.Logger is not marked as serializable for backward compatibility reasons, most if not all actual implementations of org.slf4j.Logger are serializable. Please also see glauche.de/2009/08/24 — Ceki
>>I think that CDI doesn't handle that, what's you knowledge No it does not. >>Maybe logging is not a good context for CDI injection It's a great context :) Your original code should compile with a warning, you should be just fine — Jonathan S. Fisher

apurohit apurohit · Accepted Answer · 2013-12-20T21:58:49

but this means that the logger must be re-injected after deserialization.

The CDI Container proxy is serializable. When deserialized, the proxy locates/binds to the proper injection. I would not not mark the injection point as transient; as that would prevent the container to locate/rebind the injection and results in a NPE.

this means that RequestScoped beans have their own logger instance instead of a static per class logger

If your producer method is something like the following

@RequestScoped
@Produces   
public Logger produceLog(InjectionPoint injectionPoint) {   
    return LoggerFactory.getLogger(injectionPoint.getMember().getDeclaringClass().getName());   
}

The LoggerFactory.getLogger() is creating one logger per class.

Maybe logging is not a good context for CDI injection... what are your considerations?

It is your choice.

CDI Injection and serialization

1 Answers