com.google.common.util.concurrent

Class AbstractService

java.lang.Object

com.google.common.util.concurrent.AbstractService

All Implemented Interfaces:

Service

@Beta
public abstract class AbstractService
extends Object
implements Service

Base class for implementing services that can handle doStart() and doStop() requests, responding to them with notifyStarted() and notifyStopped() callbacks. Its subclasses must manage threads manually; consider AbstractExecutionThreadService if you need only a single execution thread.

Since:

1.0

Author:

Jesse Wilson, Luke Sandberg

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	AbstractService() 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.
void	awaitRunning() Waits for the Service to reach the running state.
void	awaitRunning(long timeout, TimeUnit unit) Waits for the Service to reach the running state for no more than the given time.
void	awaitTerminated() Waits for the Service to reach the terminated state.
void	awaitTerminated(long timeout, TimeUnit unit) Waits for the Service to reach a terminal state (either terminated or failed) for no more than the given time.
protected abstract void	doStart() This method is called by start() to initiate service startup.
protected abstract void	doStop() This method should be used to initiate service shutdown.
Throwable	failureCause() Returns the Throwable that caused this service to fail.
boolean	isRunning() Returns true if this service is running.
protected void	notifyFailed(Throwable cause) Invoke this method to transition the service to the Service.State.FAILED.
protected void	notifyStarted() Implementing classes should invoke this method once their service has started.
protected void	notifyStopped() Implementing classes should invoke this method once their service has stopped.
ListenableFuture<Service.State>	start() Deprecated.
Service.State	startAndWait() Deprecated.
Service	startAsync() If the service state is Service.State.NEW, this initiates service startup and returns immediately.
Service.State	state() Returns the lifecycle state of the service.
ListenableFuture<Service.State>	stop() Deprecated.
Service.State	stopAndWait() Deprecated.
Service	stopAsync() If the service is starting or running, this initiates service shutdown and returns immediately.
String	toString() Returns a string representation of the object.

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractService

protected AbstractService()

Constructor for use by subclasses.

Method Detail

doStart

protected abstract void doStart()

This method is called by start() to initiate service startup. The invocation of this method should cause a call to notifyStarted(), either during this method's run, or after it has returned. If startup fails, the invocation should cause a call to notifyFailed(Throwable) instead.

This method should return promptly; prefer to do work on a different thread where it is convenient. It is invoked exactly once on service startup, even when start() is called multiple times.

doStop

protected abstract void doStop()

This method should be used to initiate service shutdown. The invocation of this method should cause a call to notifyStopped(), either during this method's run, or after it has returned. If shutdown fails, the invocation should cause a call to notifyFailed(Throwable) instead.

This method should return promptly; prefer to do work on a different thread where it is convenient. It is invoked exactly once on service shutdown, even when stop() is called multiple times.

startAsync

public final Service startAsync()

Description copied from interface: Service

If the service state is Service.State.NEW, this initiates service startup and returns immediately. A stopped service may not be restarted.

Specified by:

startAsync in interface Service

Returns:

this

start

@Deprecated
public final ListenableFuture<Service.State> start()

Deprecated.

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.

stopAsync

public final Service stopAsync()

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:

stopAsync in interface Service

Returns:

this

stop

@Deprecated
public final ListenableFuture<Service.State> stop()

Deprecated.

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

@Deprecated
public Service.State startAndWait()

Deprecated.

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

@Deprecated
public Service.State stopAndWait()

Deprecated.

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.

awaitRunning

public final void awaitRunning()

Description copied from interface: Service

Waits for the Service to reach the running state.

Specified by:

awaitRunning in interface Service

awaitRunning

public final void awaitRunning(long timeout,
                TimeUnit unit)
                        throws TimeoutException

Description copied from interface: Service

Waits for the Service to reach the running state for no more than the given time.

Specified by:

awaitRunning in interface Service

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Throws:

TimeoutException - if the service has not reached the given state within the deadline

awaitTerminated

public final void awaitTerminated()

Description copied from interface: Service

Waits for the Service to reach the terminated state.

Specified by:

awaitTerminated in interface Service

awaitTerminated

public final void awaitTerminated(long timeout,
                   TimeUnit unit)
                           throws TimeoutException

Description copied from interface: Service

Waits for the Service to reach a terminal state (either terminated or failed) for no more than the given time.

Specified by:

awaitTerminated in interface Service

Parameters:

timeout - the maximum time to wait

unit - the time unit of the timeout argument

Throws:

TimeoutException - if the service has not reached the given state within the deadline

notifyStarted

protected final void notifyStarted()

Implementing classes should invoke this method once their service has started. It will cause the service to transition from Service.State.STARTING to Service.State.RUNNING.

Throws:

IllegalStateException - if the service is not Service.State.STARTING.

notifyStopped

protected final void notifyStopped()

Implementing classes should invoke this method once their service has stopped. It will cause the service to transition from Service.State.STOPPING to Service.State.TERMINATED.

Throws:

IllegalStateException - if the service is neither Service.State.STOPPING nor Service.State.RUNNING.

notifyFailed

protected final void notifyFailed(Throwable cause)

Invoke this method to transition the service to the Service.State.FAILED. The service will not be stopped if it is running. Invoke this method when a service has failed critically or otherwise cannot be started nor stopped.

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

failureCause

public final Throwable failureCause()

Description copied from interface: Service

Returns the Throwable that caused this service to fail.

Specified by:

failureCause in interface Service

Since:

14.0

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

Since:

13.0

toString

public String toString()

Description copied from class: java.lang.Object

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Overrides:

toString in class Object

Returns:

a string representation of the object.