com.google.common.util.concurrent

Class ForwardingService

java.lang.Object

com.google.common.collect.ForwardingObject

com.google.common.util.concurrent.ForwardingService

All Implemented Interfaces:

Service

@Beta
public abstract class ForwardingService
extends ForwardingObject
implements Service

A Service that forwards all method calls to another service.

Since:

1.0

Author:

Chris Nokleberg

Nested Class Summary

Nested classes/interfaces inherited from interface com.google.common.util.concurrent.Service

Service.Listener, Service.State

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ForwardingService() Constructor for use by subclasses.

Method Summary

Methods

Modifier and Type	Method and Description
void	addListener(Service.Listener listener, Executor executor) Registers a Service.Listener to be executed on the given executor.
protected abstract Service	delegate() Returns the backing delegate instance that methods are forwarded to.
boolean	isRunning() Returns true if this service is running.
protected Service.State	standardStartAndWait() A sensible default implementation of startAndWait(), in terms of start().
protected Service.State	standardStopAndWait() A sensible default implementation of stopAndWait(), in terms of stop().
ListenableFuture<Service.State>	start() If the service state is Service.State.NEW, this initiates service startup and returns immediately.
Service.State	startAndWait() Initiates service startup (if necessary), returning once the service has finished starting.
Service.State	state() Returns the lifecycle state of the service.
ListenableFuture<Service.State>	stop() If the service is starting or running, this initiates service shutdown and returns immediately.
Service.State	stopAndWait() Initiates service shutdown (if necessary), returning once the service has finished stopping.

Methods inherited from class com.google.common.collect.ForwardingObject

toString

Methods inherited from class java.lang.Object

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

Constructor Detail

ForwardingService

protected ForwardingService()

Constructor for use by subclasses.

Method Detail

delegate

protected abstract Service delegate()

Description copied from class: ForwardingObject

Returns the backing delegate instance that methods are forwarded to. Abstract subclasses generally override this method with an abstract method that has a more specific return type, such as ForwardingSet.delegate(). Concrete subclasses override this method to supply the instance being decorated.

Specified by:

delegate in class ForwardingObject

start

public ListenableFuture<Service.State> start()

Description copied from interface: Service

If the service state is Service.State.NEW, this initiates service startup and returns immediately. If the service has already been started, this method returns immediately without taking action. A stopped service may not be restarted.

Specified by:

start in interface Service

Returns:

a future for the startup result, regardless of whether this call initiated startup. Calling Future.get() will block until the service has finished starting, and returns one of Service.State.RUNNING, Service.State.STOPPING or Service.State.TERMINATED. If the service fails to start, Future.get() will throw an ExecutionException, and the service's state will be Service.State.FAILED. If it has already finished starting, Future.get() returns immediately. Cancelling this future has no effect on the service.

state

public Service.State state()

Description copied from interface: Service

Returns the lifecycle state of the service.

Specified by:

state in interface Service

stop

public ListenableFuture<Service.State> stop()

Description copied from interface: Service

If the service is starting or running, this initiates service shutdown and returns immediately. If the service is new, it is terminated without having been started nor stopped. If the service has already been stopped, this method returns immediately without taking action.

Specified by:

stop in interface Service

Returns:

a future for the shutdown result, regardless of whether this call initiated shutdown. Calling Future.get() will block until the service has finished shutting down, and either returns Service.State.TERMINATED or throws an ExecutionException. If it has already finished stopping, Future.get() returns immediately. Cancelling this future has no effect on the service.

startAndWait

public Service.State startAndWait()

Description copied from interface: Service

Initiates service startup (if necessary), returning once the service has finished starting. Unlike calling start().get(), this method throws no checked exceptions, and it cannot be interrupted.

Specified by:

startAndWait in interface Service

Returns:

the state of the service when startup finished.

stopAndWait

public Service.State stopAndWait()

Description copied from interface: Service

Initiates service shutdown (if necessary), returning once the service has finished stopping. If this is Service.State.STARTING, startup will be cancelled. If this is Service.State.NEW, it is terminated without having been started nor stopped. Unlike calling stop().get(), this method throws no checked exceptions.

Specified by:

stopAndWait in interface Service

Returns:

the state of the service when shutdown finished.

isRunning

public boolean isRunning()

Description copied from interface: Service

Returns true if this service is running.

Specified by:

isRunning in interface Service

addListener

public void addListener(Service.Listener listener,
               Executor executor)

Description copied from interface: Service

Registers a Service.Listener to be executed on the given executor. The listener will have the corresponding transition method called whenever the service changes state. The listener will not have previous state changes replayed, so it is suggested that listeners are added before the service starts.

There is no guaranteed ordering of execution of listeners, but any listener added through this method is guaranteed to be called whenever there is a state change.

Exceptions thrown by a listener will be propagated up to the executor. Any exception thrown during Executor.execute (e.g., a RejectedExecutionException or an exception thrown by inline execution) will be caught and logged.

Specified by:

addListener in interface Service

Parameters:

listener - the listener to run when the service changes state is complete

executor - the executor in which the the listeners callback methods will be run. For fast, lightweight listeners that would be safe to execute in any thread, consider MoreExecutors.sameThreadExecutor().

standardStartAndWait

protected Service.State standardStartAndWait()

A sensible default implementation of startAndWait(), in terms of start(). If you override start(), you may wish to override startAndWait() to forward to this implementation.

Since:

9.0

standardStopAndWait

protected Service.State standardStopAndWait()

A sensible default implementation of stopAndWait(), in terms of stop(). If you override stop(), you may wish to override stopAndWait() to forward to this implementation.

Since:

9.0