REST and JAVA JPA

Question

I am trying to understand the code of some project which is not properly documented.Am the only developer working on the task.I dont have much experience. There is a data model and there are some classes witten to access it.It was mentioned that the data model has some rest api on top of it.But when i see the code i can see getter code which makes some rest call to some uri. But i look at setter methods it has plain jpa used to persisit the object. ex extitymanger.persist(objname).

Now is it possible to use REST interface for getting the data and using JPA to persiste the data?

Answer 1

That's definitely possible. It sounds like the access classes are abstracting around a database for storage. Thus it's behaving like a DAO and using JPA to access the datasource. For the getters your access class is using an exposed REST interface from some service. So rather than using JPA to query and return the data, it's using a service that's performing the same tasks.

Maybe the REST interface is a get only and doesn't provide a mechanism for storing data and that's why the direct JPA is used.

Answer 2

Yes, it is possible. Without knowing more it is not possible to know if it is effective. My instincts tell me it is not the best solution.

Answer 3

It is possible to use JPA for all the rest operations. You can check out an example I posted to my blog:

• Part 1 - The Database
• Part 2 - Mapping the Database to JPA Entities
• Part 3 - Mapping JPA entities to XML (using JAXB)
• Part 4 - The RESTful Service
• Part 5 - The Client

Answer 4

I think the best thing to do is to forget trying to work out the individual pieces of code and focus on the big picture. Work out all of the inputs and all of the outputs. Even write some test cases to test various inputs create various outputs.

That way you can understand what the code does without needing to know all of the minor ddetails.