Structure of the project

Here there is a picture of the architecture of the project that I will implement. 

Mainly the structure is divided into three tiers:

A persistence tier to manage the persistence of the data objects, a business tier, that contains all the logic used in the application  and the web tier where there are the html pages and the servlets that access to the business logic implemented in the EJB using the Business Delegate pattern.

So from this picture can be understand also the design patterns that I will adopt to develop the application. In particular I will use:

• DAO pattern: has the purpose to separate the business logic from the logic to access the data.
• DTO pattern: reduce the network overhead transmitting an entire entity in one call instead of transmitting  each field of the entity.
• Session Facade pattern: expose an interface of the business logic, hiding the implementation  details and the complexity of the business tier. 
• Service locator pattern: hide the mechanisms of the lookup to the client.
• Business Delegate pattern: decouples business components from the clients.