128. Building and Running a Function

The sample @SpringBootApplication above has a function that can be decorated at runtime by Spring Cloud Function to be an HTTP endpoint, or a Stream processor, for instance with RabbitMQ, Apache Kafka or JMS.

The @Beans can be Function, Consumer or Supplier (all from java.util), and their parametric types can be String or POJO.

Functions can also be of Flux<String> or Flux<Pojo> and Spring Cloud Function takes care of converting the data to and from the desired types, as long as it comes in as plain text or (in the case of the POJO) JSON. There is also support for Message<Pojo> where the message headers are copied from the incoming event, depending on the adapter. The web adapter also supports conversion from form-encoded data to a Map, and if you are using the function with Spring Cloud Stream then all the conversion and coercion features for message payloads will be applicable as well.

Functions can be grouped together in a single application, or deployed one-per-jar. It’s up to the developer to choose. An app with multiple functions can be deployed multiple times in different "personalities", exposing different functions over different physical transports.