io.elastic.api

Class Component

java.lang.Object

io.elastic.api.Component

public abstract class Component
extends java.lang.Object

A component is an unit implementing a custom business logic to be executed in the elastic.io runtime.

A component is executed with a ExecutionParameters which provides the component with a Message, configuration and a snapshot.

The given Message represents component's input. Besides other things it contains a payload to be consumed by a component.

A configuration is an instance JsonObject containing required information, such as API key or username/password combination, that components needs to collect from user to function properly.

A snapshot is an instance of JsonObject that represents component's state. For example, a Twitter timeline component might store the id of the last retrieved tweet for the next execution in order to ask Twitter for tweets whose ids are greater than the one in the snapshot.

A component communicates with elastic.io runtime by emitting events, such as data, error, etc. For more info please check out EventEmitter.

The following example demonstrates a simple component which echos the incoming message.

 

 public class EchoComponent extends Component {

    public EchoComponent(EventEmitter eventEmitter) {
       super(eventEmitter);
    }

    @Override
    public void execute(ExecutionParameters parameters) {

       final JsonObject snapshot = new JsonObject();
       snapshot.add("echo", parameters.getSnapshot());

       getEventEmitter()
          .emitSnapshot(snapshot)
          .emitData(echoMessage(parameters));
    }

    private Message echoMessage(ExecutionParameters parameters) {

       final Message msg = parameters.getMessage();

       final JsonObject body = new JsonObject();
       body.add("echo", msg.getBody());
       body.add("config", parameters.getConfiguration());

       return new Message.Builder()
                   .body(body)
                   .attachments(msg.getAttachments())
                   .build();
    }
 }
 
 

See Also:

ExecutionParameters, Message, EventEmitter

Constructor Summary

Constructors

Constructor and Description
Component(EventEmitter eventEmitter) Creates a component instance with the given EventEmitter.

Method Summary

Modifier and Type	Method and Description
abstract void	execute(ExecutionParameters parameters) Executes this component with the given ExecutionParameters.
protected EventEmitter	getEventEmitter() Used to emit data to component's callee by sending events.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Component

public Component(EventEmitter eventEmitter)

Creates a component instance with the given EventEmitter.

Parameters:

eventEmitter - emitter to emit events

Method Detail

execute

public abstract void execute(ExecutionParameters parameters)

Executes this component with the given ExecutionParameters.

Parameters:

parameters - parameters to execute component with

getEventEmitter

protected EventEmitter getEventEmitter()

Used to emit data to component's callee by sending events.

Returns:

instance of EventEmitter