How to Inject Stateless EJBs into JAX-RS Web Services?

Injecting EJBs into JAX-RS Web Services

Issue Description:

In an attempt to inject a Stateless EJB into a JAX-RS web service using annotations, the EJB instance remains null in the service class, resulting in a NullPointerException upon use.

Environment Details:

• Glassfish 3.1
• Netbeans 6.9 RC 2
• Java EE 6

Solution Options:

Option 1: Inject using the Injection Provider SPI

• Implement a custom injection provider that performs the EJB lookup and injection.
• For example, in Jersey 1.17:

import com.sun.jersey.core.spi.component.ComponentContext;
import ...
public class EJBProvider implements InjectableProvider<EJB, Type> {
    // Implementation details...
}

Option 2: Convert the Resource Class to an EJB

• Make the JAX-RS resource class a Stateless EJB itself, allowing it to manage its own dependencies.

Option 3: Leverage CDI

• Use Context and Dependency Injection (CDI) to inject the EJB into the JAX-RS resource class.

Example:

@Path("book")
@RequestScoped
public class BookResource {
    @Inject
    private BookEJB bookEJB;
    // Implementation details...
}

Additional Resources:

• [EJB Injection](https://docs.oracle.com/javaee/7/api/javax/ejb/EJB.html)
• [@EJB Injection](https://stackoverflow.com/questions/1130846/ejb-injection)
• [Combining REST Services with EJB 3.1](https://dzone.com/articles/combining-rest-services-with-ejb-31)
• [EJB 3.1 and REST - The Lightweight Hybrid](https://weblogs.java.net/blog/emcfarlane/archive/2009/12/10/ejb-31-and-rest-lightweight-hybrid)
• [Injecting an EJB from a jar into a jax-rs class in a war](https://stackoverflow.com/questions/6474811/injecting-an-ejb-from-a-jar-into-a-jax-rs-class-in-a-war)

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