Java Enterprise Best Practices

Use Standard Design Architecture

As I mentioned earlier, it is usually a good idea to design most of the application before implementing it. This is especially true of J2EE applications, which regularly contain many different components.

Even though every developer or system architect has a unique approach to application design, most people follow some general principles. The first of these principles is the layered structure of a J2EE application:

Presentation layer

This is the UI of the application. It usually contains servlets, JSP files, applets, and various presentation and display logic. This layer is considered to be a client of the business logic layer because it exclusively uses that layer to complete its operations.

Business logic layer

This is the most important layer of the application, at least from the perspective of an EJB programmer. This layer contains the business workflow and various services used by the client. It relies on the persistence layer for storing and retrieving data.

Persistence layer

This layer is obviously used to persist application data. Most of the code here will comprise entity beans, and possibly some other layers of persistence abstraction, such as data access objects (which abstract the source of the data).

These layers are by no means set in stone. You might encounter a situation in which adding an additional logical layer will make the application design cleaner and easier to implement. Or you might find that you don’t need a presentation ...