Package org.eclipse.microprofile.reactive.messaging.spi

Interface OutgoingConnectorFactory

All Superinterfaces:
ConnectorFactory
public interface OutgoingConnectorFactory extends ConnectorFactory
SPI used to implement a connector managing a sink of messages for a specific transport. For example, to handle dispatch messages to Kafka, the reactive messaging extension would implement a bean implementing this interface. This bean is called for every stream that needs to be created for this specific transport (so Kafka in this example). These streams are connected to methods annotated with Outgoing.

The factory is called to create a subscriber for each configured transport. The configuration is done using MicroProfile Config. The following snippet gives an example for a hypothetical Kafka connector: 

 mp.messaging.outgoing.my-channel.connector=acme.kafka
 mp.messaging.outgoing.my-channel.topic=my-topic
 mp.messaging.connector.acme.kafka.bootstrap.servers=localhost:9092
 ...

The configuration keys are structured as follows: mp.messaging.[incoming|outgoing].channel-name.attribute or mp.messaging.[connector].connector-name.attribute. Channel names are not expected to contain . so the first occurrence of a . in the channel-name portion of a property terminates the channel name and precedes the attribute name. For connector attributes, the longest string, inclusive of .s, that matches a loadable connector is used as a connector-name. The remainder, after a . separator, is the attribute name. Configuration keys that begin mp.messaging.incoming are not used for OutgoingConnectorFactory configuration.

The channel-name segment in the configuration key corresponds to the name of the channel used in the Outgoing annotation: 

 @Outgoing("my-channel")
 public CompletionStage<String> produce(String s) {
      // ...
 }

The set of attributes depend on the connector and transport layer (For example, bootstrap.servers is Kafka specific). The connector attribute indicates the name of the connector. It will be matched to the value returned by the Connector qualifier used on the relevant OutgoingConnectorFactory bean implementation. This is how a reactive messaging implementation looks for the specific OutgoingConnectorFactory required for a channel. Any mp.messaging.connector attributes for the channel's connector are also included in the set of relevant attributes. Where an attribute is present for both a channel and its connector the value of the channel specific attribute will take precedence. In the previous configuration, the reactive messaging implementation would need to find the OutgoingConnectorFactory implementation qualified with the Connector qualifier with the value acme.kafka to create the my-channel subscriber. Note that if the connector cannot be found, the deployment must be failed with a DeploymentException.

The getSubscriberBuilder(Config) is called for every channel that needs to be created. The Config object passed to the method contains a subset of the global configuration, and with the prefixes removed. So for the previous configuration, it would be: 

 bootstrap.servers = localhost:9092
 topic = my-topic

So the connector implementation can retrieve the value with Config.getValue(String, Class) and Config.getOptionalValue(String, Class).

If the configuration is invalid, the getSubscriberBuilder(Config) method must throw an IllegalArgumentException, caught by the reactive messaging implementation and triggering a failure in the deployment.

Note that a Reactive Messaging implementation must support the configuration format described here. Implementations are free to provide additional support for other approaches.