Basics

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Handle event input

Sends an incoming even to the EventProcessor to trigger a new stream calculation. Any method annotated with @OnEvent receives the event from the event processor

See sample - WrapNode.java

public class WrapNode {
    public static class MyNode {
        @OnEventHandler
        public boolean handleStringEvent(String stringToProcess) {
            System.out.println("received:" + stringToProcess);
            return true;
        }
    }

    public static void main(String[] args) {
        var processor = DataFlowBuilder
                .subscribeToNode(new MyNode())
                .build();

        processor.onEvent("TEST");
    }
}

Output

received:TEST

Handle multiple event types

An event handler class can handle multiple event types. Add as many handler methods as required and annotate each method with an @OnEvent annotation.

See sample - MultipleEventTypes.java

public class MultipleEventTypes {

    public static class MyNode {
        @OnEventHandler
        public boolean handleStringEvent(String stringToProcess) {
            System.out.println("String received:" + stringToProcess);
            return true;
        }

        @OnEventHandler
        public boolean handleIntEvent(int intToProcess) {
            System.out.println("Int received:" + intToProcess);
            return true;
        }
    }

    public static void main(String[] args) {
        var processor = DataFlowBuilder
                .subscribeToNode(new MyNode())
                .build();

        processor.onEvent("TEST");
        processor.onEvent(16);
    }
}

Output

String received:TEST
Int received:16

Handling unknown event types

An unknown event handler can be registered at runtime with the event processor, to catch any event types that are not handled by the processor. Register the unKnownEventHandler with:

[processor].setUnKnownEventHandler(Consumer<T> consumer)

See sample - UnknownEventHandling.java

public class UnknownEventHandling {

    public static void main(String[] args) {
        var processor = DataFlowBuilder
                .subscribeToNode(new MyNode())
                .build();

        //set an unknown event handler
        processor.setUnKnownEventHandler(e -> System.out.println("Unregistered event type -> " + e.getClass().getName()));
        processor.onEvent("TEST");

        //handled by unKnownEventHandler
        processor.onEvent(Collections.emptyList());
    }

    public static class MyNode {
        @OnEventHandler
        public boolean handleStringEvent(String stringToProcess) {
            System.out.println("received:" + stringToProcess);
            return true;
        }
    }
}

Output

received:TEST
Unregistered event type -> java.util.Collections$EmptyList