Question

I’ve participated in several projects of Spring-based web-application – and have written a quantity myself. Usually we have (roughly speaking) following folders to divide our classes by categories like dao, models, web (for controllers if we use Spring MVC or backing beans for JSF for example) and also service – here we keep what we think is business-logic (even when sometimes classes here simply forward methods to dao).

Now I am faced with development of EJB application – I’ve learnt that I will have some web and model classes anyway. Also I may use dedicated dao layer or may put data access into facades (I prefer dedicated folder though it increases verbosity).

But I do not understand clearly whether facades are exactly the place to put business-logic in it, or I should add services folder for it and use facades more like dao (eliminating dao itself).

I also would be glad for short and comprehensive compilation of hints on EJB application architecture.

Answer 1

I would go with a similar setup with EJB as you have done with Spring. You have your web package (MVC stuff), then your service layer which contains most business logic and then DAO layer which contains basic CRUD operations and some database queries.

In this scenario you can test the possibly complex business logic in the session beans with fast unit tests that don’t need database and you can mock the DAO access here. Then you can have relatively simple tests for your DAO layer, so the number of tests requiring database (ie. that are consirably slower) is smaller.

Normally I would call facade a set of session beans that offer simple methods for operating the system via for example Web services. These beans would use the normal service layer beans. With just a web layer and no integration layers I don’t see a reason to create an extra facade layer.