The purpose of this article is to present how to design, test, and monitor a REST service client. The article includes a repository with clients written in Kotlin using various technologies such as WebClient, RestClient, Ktor Client, Retrofit. It demonstrates how to send and retrieve data from an external service, add a cache layer, and parse the received response into domain objects.
We’re all familiar with TDD, or at least write unit tests for our software, but unit tests won’t check application state after complex UI interactions. If you want to make sure that an application behaves correctly when users interact with it, then you need to write UI tests.
SOA (Service Oriented Architecture) as a modern approach to build distributed enterprise applications gives us many benefits, including resiliency and fault-tolerance. On the other hand, there are many new kinds of SOA-specific faults, like publishing, discovery, composition, binding or execution faults (as stated in A Fault Taxonomy for Service-Oriented Architecture). Error handling is one of the most important things to have services right designed and implemented (see article Error Handling Considerations in SOA Analysis & Design). In this article, I want to focus only on a small aspect of this broad subject: unexpected service behaviors which, if not properly handled by the client, can lead to application inaccessibility.
