Here are some tips when authoring web service clients:
- Decouple connectivity from request construction. This will isolate variations in input construction and the mechanics of service invocation cleanly separated. Additionally, the request construction might depend on the particular resource – e.g. they can be set of query string parameters or a more complex object structure.
- Connectivity logic should encapsulate the service URL and automatic-retry considerations. The client can automatically retry GET requests specified number of times if invocation encounters a connection timeout. It should also ensure response is OK (either via HTTP status codes or by examining appropriate response-specific data structures).
- Don’t swallow exceptions – the service might return a resource not found or an internal server error – the code that is using the client should be given the flexibility to deal with these exceptions appropriately – the client code shouldn’t assume or mask these exceptions. When in doubt, don’t suppress runtime exceptions.
- Decouple domain logic from service client – domain logic might dictate whether or not a service call needs to be made, or the nature of input resource data, etc. – this logic is more likely to change per the consuming application’s evolving requirements and shouldn’t be hosting service invocation code in the same class.
- Provide reusable API hooks for addressing cross-cutting concerns – such as response time capture and input and output messages – if you want to report response time trends when invoking a service you will not want to clutter this all over the consuming application’s codebase – the client can and should centralize these.
Remember the above is useful whether you are consuming a service or providing clients for your prospective service consumers.