com.google.common.util.concurrent
Class AbstractIdleService

java.lang.Object
  com.google.common.util.concurrent.AbstractIdleService

All Implemented Interfaces:

Service

@Beta
public abstract class AbstractIdleService
extends Object
implements Service

Base class for services that do not need a thread while "running" but may need one during startup and shutdown. Subclasses can implement startUp() and shutDown() methods, each which run in a executor which by default uses a separate thread for each method.

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

AbstractIdleService()

Method Summary

void	addListener(Service.Listener listener, Executor executor) Registers a Service.Listener to be executed on the given executor.
protected Executor	executor(Service.State state) Returns the Executor that will be used to run this service.
boolean	isRunning() Returns true if this service is running.
protected abstract void	shutDown() Stop the service.
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.
protected abstract void	startUp() Start the service.
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.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractIdleService

public AbstractIdleService()

Method Detail

startUp

protected abstract void startUp()
                         throws Exception

Start the service.

Throws:

Exception

shutDown

protected abstract void shutDown()
                          throws Exception

Stop the service.

Throws:

Exception

executor

protected Executor executor(Service.State state)

Returns the Executor that will be used to run this service. Subclasses may override this method to use a custom Executor, which may configure its worker thread with a specific name, thread group or priority. The returned executor's execute() method is called when this service is started and stopped, and should return promptly.

Parameters:

state - Service.State.STARTING or Service.State.STOPPING, used by the default implementation for naming the thread

toString

public String toString()

Overrides:

toString in class Object

start

public final 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.

startAndWait

public final 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.

isRunning

public final boolean isRunning()

Description copied from interface: Service

Returns true if this service is running.

Specified by:

isRunning in interface Service

state

public final Service.State state()

Description copied from interface: Service

Returns the lifecycle state of the service.

Specified by:

state in interface Service

stop

public final 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.

stopAndWait

public final 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.

addListener

public final 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().