Web Services: A Java™ Developer’s Guide Using E-Speak

5.2. Contracts

In the previous chapters, you saw how services developed business logic to abide by the service interface. In those cases, the entities creating the service interface and implementation (and even client) were all one and the same. Until now, interfaces have been merely a means to allow the clients to interact with the service. The interfaces defined a set of methods that the service implemented and could then be invoked by the client, once the client received the handle to the service. Also recall that a prior out-of-band interaction had to take place between the service deployer and client, which gave the client the service stub. The client already knew what the methods and the invocation sequence were and simply needed to establish ...