@Beta @GwtIncompatible public abstract class AbstractService extends Object implements Service
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.Service.Listener, Service.State
Modifier | Constructor and Description |
---|---|
protected |
AbstractService()
Constructor for use by subclasses.
|
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 void |
doCancelStart()
This method is called by
stopAsync() when the service is still starting (i.e. |
protected abstract void |
doStart()
This method is called by
startAsync() 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.
|
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.
|
Service |
stopAsync()
|
String |
toString()
Returns a string representation of the object.
|
protected AbstractService()
@ForOverride protected abstract void doStart()
startAsync()
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 startAsync()
is
called multiple times.
@ForOverride protected abstract void doStop()
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 stopAsync()
is
called multiple times.
If stopAsync()
is called on a Service.State.STARTING
service, this method is not
invoked immediately. Instead, it will be deferred until after the service is Service.State.RUNNING
. Services that need to cancel startup work can override {#link #doCancelStart}.
@ForOverride protected void doCancelStart()
stopAsync()
when the service is still starting (i.e. startAsync()
has been called but notifyStarted()
has not). Subclasses can override the
method to cancel pending work and then call notifyStopped()
to stop the service.
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 stopAsync()
is
called multiple times.
When this method is called state()
will return Service.State.STOPPING
, which is the
external state observable by the caller of stopAsync()
.
@CanIgnoreReturnValue public final Service startAsync()
Service
Service.State.NEW
, this initiates service startup and returns
immediately. A stopped service may not be restarted.startAsync
in interface Service
@CanIgnoreReturnValue public final Service stopAsync()
Service
public final void awaitRunning()
Service
Service
to reach the running state.awaitRunning
in interface Service
public final void awaitRunning(long timeout, TimeUnit unit) throws TimeoutException
Service
Service
to reach the running state for no more
than the given time.awaitRunning
in interface Service
timeout
- the maximum time to waitunit
- the time unit of the timeout argumentTimeoutException
- if the service has not reached the given state within the deadlinepublic final void awaitTerminated()
Service
Service
to reach the terminated state.awaitTerminated
in interface Service
public final void awaitTerminated(long timeout, TimeUnit unit) throws TimeoutException
Service
Service
to reach a terminal state (either terminated
or failed
) for no more than the given time.awaitTerminated
in interface Service
timeout
- the maximum time to waitunit
- the time unit of the timeout argumentTimeoutException
- if the service has not reached the given state within the deadlineprotected final void notifyStarted()
Service.State.STARTING
to Service.State.RUNNING
.IllegalStateException
- if the service is not Service.State.STARTING
.protected final void notifyStopped()
Service.State.STARTING
or Service.State.STOPPING
to Service.State.TERMINATED
.IllegalStateException
- if the service is not one of Service.State.STOPPING
, Service.State.STARTING
, or Service.State.RUNNING
.protected final void notifyFailed(Throwable cause)
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.public final boolean isRunning()
Service
true
if this service is running.public final Service.State state()
Service
public final Throwable failureCause()
Service
Throwable
that caused this service to fail.failureCause
in interface Service
public final void addListener(Service.Listener listener, Executor executor)
Service
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.
addListener
guarantees execution ordering across calls to a given listener but not
across calls to multiple listeners. Specifically, a given listener will have its callbacks
invoked in the same order as the underlying service enters those states. Additionally, at most
one of the listener's callbacks will execute at once. However, multiple listeners' callbacks
may execute concurrently, and listeners may execute in an order different from the one in which
they were registered.
RuntimeExceptions thrown by a listener will be caught and logged. Any exception thrown
during Executor.execute
(e.g., a RejectedExecutionException
) will be caught and
logged.
addListener
in interface Service
listener
- the listener to run when the service changes state is completeexecutor
- 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.directExecutor()
.public String toString()
java.lang.Object
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())
Copyright © 2010–2019. All rights reserved.