Package io.elastic.api

Interface Function

public interface Function

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 Function {


    @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	Description
void	execute(ExecutionParameters parameters)	Executes this component with the given ExecutionParameters.
default void	init(InitParameters parameters)	Used to initialize a component before message processing.
default void	shutdown(ShutdownParameters parameters)	Used to shutdown a component gracefully before its process is killed.
default jakarta.json.JsonObject	startup(StartupParameters parameters)	Used to initialize the component on flow start.

Method Details

execute

void execute(ExecutionParameters parameters)

Executes this component with the given ExecutionParameters.

Parameters:

parameters - parameters to execute component with

startup

default jakarta.json.JsonObject startup(StartupParameters parameters)

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. The persisted JSON will be passed to shutdown(ShutdownParameters) method where the subscription can be canceled on flow stop.

Parameters:

parameters - parameters to startup the module with

Returns:

state to be persisted

Since:

2.0.0

init

default void init(InitParameters parameters)

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:

parameters - to init the module with

Since:

2.0.0

shutdown

default void shutdown(ShutdownParameters parameters)

Used to shutdown a component gracefully before its process is killed. This method is invoked when the flow the component is used in is inactivated. It is considered as the counterpart of startup(StartupParameters). For example, this method may be used to cancel a webhook subscription on flow stop.

Parameters:

parameters - parameters to shutdown the module with

Since:

2.2.0