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. A
Function is exposed as an HTTP POST if spring-cloud-function-web
is on the classpath, and as a Spring Cloud Stream Processor if
spring-cloud-function-stream is on the classpath and a
spring.cloud.function.stream.endpoint property is configured in the Spring
environment. A Consumer is also exposed as an HTTP POST, or as a Stream
Sink. A Supplier translates to an HTTP GET, or a Stream Source.
Functions can 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. TBD: support for Flux<Message<Pojo>> and maybe plain
Pojo types (Fluxes implied and implemented by the framework).
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.