Services form the layer that defines a set of Middleware operations available to the client tier. In other words, a service is an entry point to the Middleware business logic. In a service, you can manage transactions, check user permissions, work with the database or delegate execution to other managed beans of the middle tier.

Below is a class diagram which shows the components of a service:

The service interface is located in the global module and is available for both middle and client tiers. At runtime, a proxy is created for the service interface on the client tier. The proxy provides invocation of service bean methods using Spring HTTP Invoker mechanism.

The service implementation bean is located in the core module and is available on the middle tier only.

ServiceInterceptor is called automatically for any service method using Spring AOP. It checks the availability of the user session for the current thread, and transforms and logs exceptions if the service is called from the client tier.