Package org.axonframework.commandhandling

Class SimpleCommandBus

java.lang.Object

org.axonframework.commandhandling.SimpleCommandBus

All Implemented Interfaces:

CommandBus, MessageDispatchInterceptorSupport<CommandMessage<?>>, MessageHandlerInterceptorSupport<CommandMessage<?>>

Direct Known Subclasses:

AsynchronousCommandBus

public class SimpleCommandBus
extends Object
implements CommandBus

Implementation of the CommandBus that dispatches commands to the handlers subscribed to that specific command's name. Interceptors may be configured to add processing to commands regardless of their type or name, for example logging, security (authorization), sla monitoring, etc.

Since:

0.5

Author:

Allard Buijze, Martin Tilma

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	SimpleCommandBus.Builder	Builder class to instantiate a SimpleCommandBus.

Constructor Summary

Constructors

Modifier	Constructor	Description
protected	SimpleCommandBus(SimpleCommandBus.Builder builder)	Instantiate a SimpleCommandBus based on the fields contained in the SimpleCommandBus.Builder.

Method Summary

Modifier and Type	Method	Description
static SimpleCommandBus.Builder	builder()	Instantiate a Builder to be able to create a SimpleCommandBus.
<C> void	dispatch(CommandMessage<C> command)	Dispatch the given command to the CommandHandler subscribed to the given command's name.
<C, R> void	dispatch(CommandMessage<C> command, CommandCallback<? super C,? super R> callback)	Dispatch the given command to the CommandHandler subscribed to the given command's name.
protected <C, R> void	doDispatch(CommandMessage<C> command, CommandCallback<? super C,? super R> callback)	Performs the actual dispatching logic.
protected <C, R> void	handle(CommandMessage<C> command, MessageHandler<? super CommandMessage<?>> handler, CommandCallback<? super C,? super R> callback)	Performs the actual handling logic.
protected <C> CommandMessage<C>	intercept(CommandMessage<C> command)	Invokes all the dispatch interceptors.
Registration	registerDispatchInterceptor(MessageDispatchInterceptor<? super CommandMessage<?>> dispatchInterceptor)	Registers the given list of dispatch interceptors to the command bus.
Registration	registerHandlerInterceptor(MessageHandlerInterceptor<? super CommandMessage<?>> handlerInterceptor)	Registers the given interceptor to the command bus.
void	setRollbackConfiguration(RollbackConfiguration rollbackConfiguration)	Sets the RollbackConfiguration that allows you to change when the UnitOfWork is rolled back.
Registration	subscribe(String commandName, MessageHandler<? super CommandMessage<?>> handler)	Subscribe the given handler to commands with given commandName.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

SimpleCommandBus

protected SimpleCommandBus(SimpleCommandBus.Builder builder)

Instantiate a SimpleCommandBus based on the fields contained in the SimpleCommandBus.Builder.

Will assert that the TransactionManager, MessageMonitor and RollbackConfiguration are not null, and will throw an AxonConfigurationException if any of them is null.

Parameters:

builder - the SimpleCommandBus.Builder used to instantiate a SimpleCommandBus instance

Method Details

builder

public static SimpleCommandBus.Builder builder()

Instantiate a Builder to be able to create a SimpleCommandBus.

The TransactionManager is defaulted to a NoTransactionManager, the MessageMonitor is defaulted to a NoOpMessageMonitor, the RollbackConfiguration defaults to a RollbackConfigurationType.UNCHECKED_EXCEPTIONS, the DuplicateCommandHandlerResolver defaults to DuplicateCommandHandlerResolution.logAndOverride() and the CommandBusSpanFactory defaults to a DefaultCommandBusSpanFactory with a NoOpSpanFactory. The TransactionManager, MessageMonitor and RollbackConfiguration are hard requirements. Thus setting them to null will result in an AxonConfigurationException.

Returns:

a Builder to be able to create a SimpleCommandBus

dispatch

public <C> void dispatch(@Nonnull
 CommandMessage<C> command)

Description copied from interface: CommandBus

Dispatch the given command to the CommandHandler subscribed to the given command's name. No feedback is given about the status of the dispatching process. Implementations may return immediately after asserting a valid handler is registered for the given command.

Specified by:

dispatch in interface CommandBus

Type Parameters:

C - The payload type of the command to dispatch

Parameters:

command - The Command to dispatch

See Also:

• GenericCommandMessage.asCommandMessage(Object)

dispatch

public <C,
R> void dispatch(@Nonnull
 CommandMessage<C> command,
 @Nonnull
 CommandCallback<? super C,? super R> callback)

Description copied from interface: CommandBus

Dispatch the given command to the CommandHandler subscribed to the given command's name. When the command is processed, one of the callback's methods is called, depending on the result of the processing.

There are no guarantees about the successful completion of command dispatching or handling after the method returns. Implementations are highly recommended to perform basic validation of the command before returning from this method call.

Implementations must start a UnitOfWork when before dispatching the command, and either commit or rollback after a successful or failed execution, respectively.

Specified by:

dispatch in interface CommandBus

Type Parameters:

C - The payload type of the command to dispatch

R - The type of the expected result

Parameters:

command - The Command to dispatch

callback - The callback to invoke when command processing is complete

See Also:

• GenericCommandMessage.asCommandMessage(Object)

intercept

protected <C> CommandMessage<C> intercept(CommandMessage<C> command)

Invokes all the dispatch interceptors.

Type Parameters:

C - The type of payload contained in the CommandMessage

Parameters:

command - The original command being dispatched

Returns:

The command to actually dispatch

doDispatch

protected <C,
R> void doDispatch(CommandMessage<C> command,
 CommandCallback<? super C,? super R> callback)

Performs the actual dispatching logic. The dispatch interceptors must have been invoked at this point.

Type Parameters:

C - The type of payload of the command

R - The type of result expected from the command handler

Parameters:

command - The actual command to dispatch to the handler

callback - The callback to notify of the result

handle

protected <C,
R> void handle(CommandMessage<C> command,
 MessageHandler<? super CommandMessage<?>> handler,
 CommandCallback<? super C,? super R> callback)

Performs the actual handling logic.

Type Parameters:

C - The type of payload of the command

R - The type of result expected from the command handler

Parameters:

command - The actual command to handle

handler - The handler that must be invoked for this command

callback - The callback to notify of the result

subscribe

public Registration subscribe(@Nonnull
 String commandName,
 @Nonnull
 MessageHandler<? super CommandMessage<?>> handler)

Subscribe the given handler to commands with given commandName. If a subscription already exists for the given name, the configured DuplicateCommandHandlerResolver will resolve the command handler which should be subscribed.

Specified by:

subscribe in interface CommandBus

Parameters:

commandName - The name of the command to subscribe the handler to

handler - The handler instance that handles the given type of command

Returns:

a handle to unsubscribe the handler. When unsubscribed it will no longer receive commands.

registerHandlerInterceptor

public Registration registerHandlerInterceptor(@Nonnull
 MessageHandlerInterceptor<? super CommandMessage<?>> handlerInterceptor)

Registers the given interceptor to the command bus. All incoming commands will pass through the registered interceptors at the given order before the command is passed to the handler for processing.

Specified by:

registerHandlerInterceptor in interface MessageHandlerInterceptorSupport<CommandMessage<?>>

Parameters:

handlerInterceptor - The interceptor to invoke when commands are handled

Returns:

handle to deregister the interceptor

registerDispatchInterceptor

public Registration registerDispatchInterceptor(@Nonnull
 MessageDispatchInterceptor<? super CommandMessage<?>> dispatchInterceptor)

Registers the given list of dispatch interceptors to the command bus. All incoming commands will pass through the interceptors at the given order before the command is dispatched toward the command handler.

Specified by:

registerDispatchInterceptor in interface MessageDispatchInterceptorSupport<CommandMessage<?>>

Parameters:

dispatchInterceptor - The interceptors to invoke when commands are dispatched

Returns:

handle to deregister the interceptor

setRollbackConfiguration

public void setRollbackConfiguration(@Nonnull
 RollbackConfiguration rollbackConfiguration)

Sets the RollbackConfiguration that allows you to change when the UnitOfWork is rolled back. If not set the, RollbackConfigurationType.UNCHECKED_EXCEPTIONS will be used, which triggers a rollback on all unchecked exceptions.

Parameters:

rollbackConfiguration - a RollbackConfiguration specifying when a UnitOfWork should be rolled back