imitatefeign

Imitatefeign is a library that provides a declarative HTTP client pattern inspired by Netflix Feign. It allows developers to declare interfaces whose methods correspond to HTTP endpoints; at runtime, a dynamic proxy generates implementation that constructs and sends HTTP requests and deserializes responses into domain types. The primary goal is to reduce boilerplate code when integrating with remote REST services and to promote consistent error handling and configuration across clients.

Design and implementation: It uses interface-based contracts augmented with annotations to specify method, path, query, headers, and body. It relies on a pluggable encoder/decoder pipeline for serialization, and can integrate with one or more underlying HTTP engines. Implementations typically use runtime reflection or compile-time code generation to create proxies. The project emphasizes testability, offering hooks for mock responses or stub servers.

Features and scope: Common features include declarative method annotations, configurable HTTP timeouts, retry and circuit-breakers, custom error mapping, and support for multiplexed or streaming responses. It aims for modularity so developers can swap HTTP client backends and encoders without changing interfaces.

Usage and adoption: Often used in microservice architectures to generate REST clients with minimal code, enabling contract-driven development and easier mocking in tests. It is usually complementary to service registries and load balancing tools.

See also: Feign, Retrofit, HTTP client libraries, declarative REST clients.