io.elastic.api

Interface Module

public interface Module

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 implements Module {


    @Override
    public void execute(ExecutionParameters parameters) {

       final JsonObject snapshot = Json.createObjectBuilder()
               .add("echo", parameters.getSnapshot())
               .build();

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

    private Message echoMessage(ExecutionParameters parameters) {

       final Message msg = parameters.getMessage();

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

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

See Also:

ExecutionParameters, Message, EventEmitter

Method Summary

Modifier and Type	Method and Description
void	execute(ExecutionParameters parameters) Executes this component with the given ExecutionParameters.
default void	init(javax.json.JsonObject configuration) Used to initialize a component before message processing.
default javax.json.JsonObject	startup(javax.json.JsonObject configuration) Used to initialize the component on flow start.

Method Detail

execute

void execute(ExecutionParameters parameters)

Executes this component with the given ExecutionParameters.

Parameters:

parameters - parameters to execute component with

startup

default javax.json.JsonObject startup(javax.json.JsonObject configuration)

Used to initialize the component on flow start. For example, a webhook trigger can subscribe a webhook url to receive events from a target API inside this method. The subscription data, such as ID, can be returned from this method as JSON object for persistence in the platform. Once shutdown method is supported, the persisted JSON will be passed as argument to shutdown method where the subscription can be canceled on flow stop.

Parameters:

configuration - component's configuration

Returns:

JSON object to be persisted or null

Since:

2.0

init

default void init(javax.json.JsonObject configuration)

Used to initialize a component before message processing. For polling flows this method is called once per scheduled execution. For real-time flows this method is called once on first execution.

Parameters:

configuration - component's configuration

Since:

2.0