The program to interface principle adds flexibility to the Business Delegate design. It
may happen that you decide to switch from EJBs to an alternative remoting option such
as Burlap-Hessian or web services. In such a scenario you need a new implementation of
the business delegate. But the page controllers (which are clients of business delegates)
will remain unaffected because they use business delegate interfaces. Finally, you will
need to wire this bean in the Spring configuration to replace the EJB.
• The intermediate business delegate layer decouples the business layer from the
presentation layer. As a result, you have a more flexible and maintainable presen-
• The business delegate exposes a uniform API to the presentation tier to access
business logic. It also handles exceptions and converts them into types that the
presentation tier understands.
• With Spring dependency injection support, the development and use of the POJO
business delegate are immensely simplified.