com.diffusiondata.gateway.framework

Interface SinkHandler<T>

Type Parameters:

T - the type of object that is expected by the update(java.lang.String, T, com.diffusiondata.gateway.framework.TopicProperties) method. This should match the type that is output by the payload converter in use for the service.

All Superinterfaces:

ServiceHandler

All Known Subinterfaces:

HybridHandler<T>

public interface SinkHandler<T>
extends ServiceHandler

The interface that a sink handler must implement.

A sink handler receives updates from the framework via its update method. A sink handler will only receive updates when the service is in an ACTIVE state.

A sink handler will not receive updates until the start method has been called. It will also not receive updates if the pause method has been called and updates will not resume until the resume method is called.

An object that implements this interface must be returned when the GatewayApplication.addSink method is called. A different object must be returned for each different service. The object must implement the update method to publish any update(s) received from the framework to the back end sink.

The handler may also optionally return service specific properties via its getSinkServiceProperties() method. If it does not then defaults will be assumed.

Author:

DiffusionData Limited

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	SinkHandler.SinkServiceProperties The service properties that apply to the sink service.
static class	SinkHandler.UnsubscriptionReason The reason for an unsubscription from a Diffusion topic.

Nested classes/interfaces inherited from interface com.diffusiondata.gateway.framework.ServiceHandler

ServiceHandler.PauseReason, ServiceHandler.ResumeReason

Method Summary

Modifier and Type	Method and Description
default SinkHandler.SinkServiceProperties	getSinkServiceProperties() This is used to set topic-specific properties for topics consumed by this service.
default CompletableFuture<?>	onSubscription(String topicPath, TopicProperties topicProperties) Called when the sink service is subscribed to a Diffusion topic.
default CompletableFuture<?>	onUnsubscription(String topicPath, TopicProperties topicProperties, SinkHandler.UnsubscriptionReason reason) Called when the sink service is unsubscribed from a Diffusion topic.
CompletableFuture<?>	update(String path, T value, TopicProperties topicProperties) Called by the framework to publish a new value received from Diffusion to the sink.
Class<T>	valueType() Class of the value expected by this handler.

Methods inherited from interface com.diffusiondata.gateway.framework.ServiceHandler

pause, resume, start, stop

Method Detail

getSinkServiceProperties

default SinkHandler.SinkServiceProperties getSinkServiceProperties()
                                                            throws InvalidConfigurationException

This is used to set topic-specific properties for topics consumed by this service.

Properties can be built using a builder which can be created using DiffusionGatewayFramework.newSinkServicePropertiesBuilder().

The default implementation returns null, which means that all defaults are assumed for service properties. See the methods of SinkHandler.SinkServiceProperties.Builder for details about defaults.

Returns:

service properties or null to indicate defaults

Throws:

InvalidConfigurationException - possibly thrown by SinkHandler.SinkServiceProperties.Builder

update

CompletableFuture<?> update(String path,
                            T value,
                            TopicProperties topicProperties)

Called by the framework to publish a new value received from Diffusion to the sink.

One or more payload converters defined for the service will have been applied to the Diffusion value received from the topic to produce the sink specific value.

Parameters:

path - the path of the Diffusion topic from where the value has been received

value - the final value to publish to the sink. This value could be of different type from the type of the Diffusion topic as it could have been converted using a converter

topicProperties - the properties of the Diffusion topic from which the value has been received

Returns:

a completable future that completes successfully when the update has been performed.

If the update completes successfully, the CompletableFuture result should be null. The result type is any rather than Void to provide forward compatibility with future iterations of this API that may provide a non-null result with a more specific result type.

If the future completes exceptionally or the future fails to complete within the timeout specified in the configuration, the framework will pause the service. If the method throws an exception, it will be logged but the service will not be paused.

onSubscription

default CompletableFuture<?> onSubscription(String topicPath,
                                            TopicProperties topicProperties)

Called when the sink service is subscribed to a Diffusion topic.

This can be used to perform any required operations when a subscription to a Diffusion topic occurs.

Parameters:

topicPath - the Diffusion topic path

topicProperties - the Diffusion topic properties

Returns:

a completable future that completes successfully when any operations following topic subscription completes.

If it completes successfully, the CompletableFuture result should be null. The result type is any rather than Void to provide forward compatibility with future iterations of this API that may provide a non-null result with a more specific result type.

If the future completes exceptionally or throws an exception, it will be logged by the framework.

onUnsubscription

default CompletableFuture<?> onUnsubscription(String topicPath,
                                              TopicProperties topicProperties,
                                              SinkHandler.UnsubscriptionReason reason)

Called when the sink service is unsubscribed from a Diffusion topic.

This can be used to perform any required operations when an unsubscription from a Diffusion topic occurs.

Parameters:

topicPath - the Diffusion topic path

topicProperties - the Diffusion topic properties

reason - the reason for unsubscription

Returns:

a completable future that completes successfully when any operations following topic unsubscription completes.

If it completes successfully, the CompletableFuture result should be null. The result type is any rather than Void to provide forward compatibility with future iterations of this API that may provide a non-null result with a more specific result type.

If the future completes exceptionally or throws an exception, it will be logged by the framework.

valueType

Class<T> valueType()

Class of the value expected by this handler.

When adding a sink service, this is called by the framework to validate that the configured payload converter converts the value to the type expected by the handler.

Returns:

the class of the value expected by this handler.