server/io.spine.server.command/AbstractCommandHandler

AbstractCommandHandler

public abstract class AbstractCommandHandler extends AbstractCommandDispatcher implements CommandHandler

The abstract base for non-aggregate classes that expose command handling methods and post their results to EventBus.

A command handler is responsible for:

Changing the state of the business model in response to a command. This is done by one of the command handling methods to which the handler dispatches the command.
Producing corresponding events.
Posting events to EventBus.

Event messages are returned as values of command handling methods.

A command handler does not have its own state. So the state of the business model it changes is external to it. Even though such behaviour may be needed in some rare cases, using aggregates is a preferred way of handling commands.

This class implements CommandDispatcher dispatching messages to methods declared in the derived classes.

See also

Aggregate

CommandDispatcher

Constructors

AbstractCommandHandler

public void AbstractCommandHandler()

Functions

public DispatchOutcome dispatch(CommandEnvelope envelope)

Dispatches the command to the handler method and posts resulting events to the EventBus.

public ImmutableSet<CommandClass> messageClasses()

Obtains a set of message classes that can be processed by this dispatcher.

public ImmutableSet<EventClass> producedEvents()

Obtains classes of the events produced by this object.

public void registerWith(BoundedContext context)

Registers this instance as a part of the given Bounded Context.

public Version version()

Always returns empty version.

Inherited functions

public boolean canDispatch(E envelope)

Checks if this dispatcher can dispatch the given message.

checkNotRegistered

public void checkNotRegistered()

Verifies that this instance is NOT registered yet.

checkRegistered

public void checkRegistered()

Verifies that this instance is already registered.

dispatchesCommands

public boolean dispatchesCommands()

Verifies if this instance dispatches at least one command.

public boolean equals(Object o)

Indicates whether some other command handler is "equal to" this one.

public int hashCode()

public String id()

Obtains identity string of the dispatcher.

public boolean isRegistered()

Determines if this instance is already registered with a Bounded Context.

public Nothing nothing()

Obtains the io.spine.server.model.

protected void onError(SignalEnvelope<? extends Object, ? extends Object, ? extends Object> signal, Error error)

protected void onRejection(SignalEnvelope<? extends Object, ? extends Object, ? extends Object> signal, Event rejection)

protected void postEvents(Iterable<Event> events)

Posts passed events to EventBus.

public Any producerId()

Obtains ID packed into Any for being used in generated events.