The Motown Core is the heart of the system which keeps track of the state of the aggregates. As the Core has been built on the Axon Framework, the Core-API enables the communication with the Core through Commands and Events. This API will primarily be used by the (new to develop) add-ons in the Motown ecosystem.

The available commands to send, and events to listen for, are located in the package io.motown.domain.api.chargingstation located in the core-api project.

In order to send commands to the Core, an Axon CommandBus and CommandGatewayFactory are necessary.

Sample configuration:

    <axon:command-bus id="commandBus">
        <axon:handlerInterceptors>
            <bean class="io.motown.domain.utils.axon.CorrelationCommandHandlerInterceptor"/>
            <bean class="org.axonframework.commandhandling.interceptors.LoggingInterceptor"/>
        </axon:handlerInterceptors>
    </axon:command-bus>

    <bean id="domainCommandGateway" class="org.axonframework.commandhandling.gateway.CommandGatewayFactoryBean">
        <property name="commandBus" ref="commandBus"/>
        <!-- Interface which defines the specific commands you want to be able to send from the add on -->
        <property name="gatewayInterface" value="io.motown.ocpp.viewmodel.domain.DomainCommandGateway"/>
    </bean>

Next the defined CommandGatewayFactory can be used to send the commands. For example, to request a charging station to unlock an EVSE:

commandGateway.send(new RequestUnlockEvseCommand(new ChargingStationId("CS-001"), new EvseId(1), identityContext), new CorrelationToken());

More information regarding commands, command buses and command gateways can be found in Axon's documentation.

Listening for relevant events allows add-ons to keep track of any state changes in the aggregates, and update their own persistency layer.

You can listen for events by adding an Axon @EventHandler annotation on the method that will handle the event.

Sample code snippet of an event handling method:

    @EventHandler
    public void handle(ChargingStationCreatedEvent event) {
        LOG.debug("ChargingStationCreatedEvent creates [{}] in operator api repo", event.getChargingStationId());
        ChargingStation station = new ChargingStation(event.getChargingStationId().getId());
        repository.createOrUpdate(station);
    }

For the @EventHandler annotation to work, it requires the following entry to be present in the Spring context xml:

    <axon:annotation-config/>