Kotlin is a programming language which interoperates fully with Java and the JVM. As Axon is written in Java it can be used in conjunction with Kotlin too, offering a different feel when using the framework.
Some of Axon's API's work perfectly well in Java, but have a rather awkward feel when transitioning over to Kotlin. The goal of the Kotlin Extension is to remove that awkwardness, by providing inline and reified methods of Axon's API.
Several solutions are currently given, which can roughly be segregated into the distinct types of messages used by Axon. This thus provides a commands, events and queries section on this page.
Currently, the Kotlin Extension has been release experimentally (e.g. release 0.1.0). This means that all implementations are subject to change until a full release (e.g. a release 1.0.0) has been made.
An inlined method has been introduced on the CommandGateway which allows the introduction of a dedicated function to be invoked upon success or failure of handling the command. As such it provides a shorthand instead of using the CommandCallback directly yourself.
Here is a sample of how this can be utilized within your own project:
A simplified implementation of the Single Event Upcaster is given, which allows for a shorter implementation cycle. Making an upcaster to upcast the CardIssuedEvent from revision 0 to 1 can be written as follows:
There are multiple variants of the query method provided, for each type of ResponseType:
An inline emit method has been added to QueryUpdateEmitter to simplify emit method's call by using generics and moving the lambda predicate at the end of parameter list. This way the lambda function can be moved outside of the parentheses.