How to Inject EJBs into JAX-RS Web Services and Avoid NullPointerExceptions?

Injection of EJBs into JAX-RS Web Services

In an effort to integrate JAX-RS web services with EJBs via annotations, a common issue arises when the injected EJB remains null, leading to a NullPointerException. To address this problem, we need to further explore the options available.

Option 1: Utilize the Injection Provider SPI

An effective approach involves implementing a provider that performs the necessary lookup and injection of the EJB. This approach leverages the injection provider Service Provider Interface (SPI).

Option 2: Design the BookResource as an EJB

Alternatively, the BookResource itself can be designed as an EJB, providing a viable solution for integrating EJBs into the web service.

Option 3: Employ CDI (Contexts and Dependency Injection)

CDI offers another option for injection by incorporating the @Inject annotation. This approach aligns well with CDI's principles of managing dependencies and providing dependency injection capabilities.

For more in-depth exploration, refer to the following resources:

• [EJB Injection](https://docs.oracle.com/javaee/7/api/javax/ejb/EJB.html)
• [How to Combine REST Services with EJB 3.1](https://jaxenter.com/how-to-combine-rest-services-with-ejb-3-1-58834.html)
• [EJB 3.1 And REST - The Lightweight Hybrid](https://www.infoq.com/articles/ejb31-rest-lightweight-hybrid)
• [Injecting an EJB from a jar into a jax-rs class in a war](https://stackoverflow.com/questions/15770910/injecting-an-ejb-from-a-jar-into-a-jax-rs-class-in-a-war)

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