Abstract: In accordance with an embodiment, described herein is a system and method for enabling use of a reactive messaging client in microservice environments. A microservices (e.g., Helidon) environment provides a development framework that enables a software developer to create and use microservices. In accordance with an embodiment, the system can include a reactive messaging API, for use with long-running activities or other types of transactions associated with microservices, which enables the system to additionally support various reactive messaging features, such as, for example, transaction processing, asynchronous messaging, reactive streams, or the use of messaging channels, in a microservices environment.