Send Signal to Workflows

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It is possible to send a signal to running workflows. Sending signals is done through channels that must be described in the workflow interface, for example:

public interface HelloWorld {
    SendChannel<String> getNotificationChannel();

    String greet(@Nullable String name);
}

interface HelloWorld {
    val notificationChannel: SendChannel<String>

    fun greet(name: String?): String
}

This signal can be any serializable object of the type described in the workflow interface.

We can send an object to a running instance targeted by id:

// stub targeting a running HelloWorld workflow with a specific id
HelloWorld helloworld = client.getWorkflowById(HelloWorld.class, "05694902-5aa4-469f-824c-7015b0df906c");

// send a signal to this instance through a channnel
helloworld.getNotificationChannel().send("foobar");

// stub targeting a running HelloWorld workflow with a specific id
val helloworld: HelloWorld = client.getWorkflowById(HelloWorld::class.java, "05694902-5aa4-469f-824c-7015b0df906c")

// send a signal to this instance through a channnel
helloworld.notificationChannel.send("foobar")

or running instances targeted by tag:

// stub targeting running HelloWorld workflows with a specific tag
HelloWorld helloworld = client.getWorkflowByTag(HelloWorld.class, "foo");

// send a signal to those instances through a channnel
helloworld.getNotificationChannel().send("foobar");

// stub targeting running HelloWorld workflows with a specific tag
val helloworld: HelloWorld = client.getWorkflowByTag(HelloWorld::class.java, "tag")

// send a signal to those instances through a channnel
helloworld.notificationChannel.send("foobar")