What options do you have to communicate between the WARs in an EAR?
We have several WARs providing different webservices deployed within one EAR. For their tasks they need to communicate with the other WARs. Of course they could communicate using webservices. What other, perhaps more efficient, options are there?
EDIT: The reason for the communication is that the modules use some shared functionality, and we want to locate this functionality in only one place, since it requires a significant amount of resources. Also, this requires synchronous communication.
First, you should be clear about what is that you are sharing. You should differentiate between the service and a library.
Library lets you share the common functionality, this is what you achieve when you use log4j library for example. In that case, you setup log4j in each project that is using it.
On the other hand, you could have the centralized logging service that has its own logging configuration and lets you manage this in a single place. In this case, you need to share the service.
You can share the library by placing the jar inside each war or inside the ear.
You can share the service by being the service client. So, your web services can use another service. In that case, one web service is a client of another, achieving service composition (a common pattern in enterprise development)
If both service client and service itself reside inside the same ear, than you might avoid some overhead by calling the service “directly”, for example using the Spring’s parent context feature:
http://springtips.blogspot.com/2007/06/using-shared-parent-application-context.html
but I would advise against flattening the service because you will loose different benefits that having service in the first place provides like governance, manageability etc.