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web-servicesrestjax-rsdaojava-ee-7

Where/when should the DAOImplementation instances be located/created?

I am working on a JAX-RS project, with a DAO layer. I am not sure about which architecture to follow.

For example, let's say we have a ProductDAOImpl class that implements a ProductDAO interface, and a ProductRS class as the entrypoint for the products REST service.

Question 1
Where should the ProductDAO (actually ProductDAOImpl) instance be created?

Options:
A) In each method of the ProductRS class that needs access to the product?
B) As a member of the ProductRS class?
(Can this option introduce data races? Not sure how the container handles the REST services classes - Possibly related to question 2 below.)

Question 2
Should I use annotations for JAX-RS classes, such as @Stateless?

Question 3
What are the best practices for the architecture and class relationship in a JAX-RS application with a DAO layer and possibly a Service layer?
(Any links to study for this topic are more than welcome.)

Question 4
Should the DAO implementation classes provide static methods? (as seen here)

Implementation specific details
Using Jersey implementation of JAX-RS with Glassfish server and a DAO layer with JDBC access to the data source.

Solution

  • Question 1

    I wouldn't create instances explicitly. Usually dependency injection it is used for this reason - inject ProductDAO interface in your ProductRS class.

    Question 2 - 3

    Some examples related (although not exact) for your technology stack.

    Jersey + Spring example: https://www.mkyong.com/webservices/jax-rs/jersey-spring-integration-example/

    Jersey + Guice example: http://www.nailedtothex.org/roller/kyle/entry/lean-example-of-tomcat-82

    Guice + Hibernate example: http://www.benmccann.com/hibernate-with-jpa-annotations-and-guice/

    Jersey + Hibernate + Spring example: http://www.benchresources.net/jersey-2-x-web-service-integrating-with-spring-and-hibernate-orm-framework-using-annotation/

    Question 4

    There are no static methods in the provided link (Should we always use Asynchronous JAX-RS resources For mobile backend?)

    UPDATE

    It is recommended to avoid static methods in DAO because of difficult testing. Related discussions: