Using CDI in a singleton pattern

Question

I\'m trying to inject a logger object in a class that is implemented following a singleton approach.

The code almost looks like this:

Logger class:<

Answer 1

Injections happens after construct. So you cant use it in the constructor.

One way is to add a method annotated @PostConstruct that can will be invoked after injections.

@PostConstruct
public void init() {
    logger.info("Creating one and only one instance here!");
}

On a sidenote i Think you are aprouching the problem in the wrong way. CDI has a nice singleton support

create a class annotated @Singleton

@Singleton
public class MySingleton {

    @Inject
    Logger logger;

    @PostConstruct
    public void init() {
        logger.info("Creating one and only one instance here!");
    }

}

Above assumes you are using CDI for java ee (JSR-299).

If you are using JSR 330 Dependency Injection (guice etc.) link

You could use constructor injection:

@Singleton
public class MySingleton {


    private final Logger logger;

    @Inject
    public MySingleton (Logger logger) {
        this.logger = logger;
        logger.info("Creating one and only one instance here!");
    }
}