@Beta public abstract class AbstractExecutionThreadService extends Object implements Service
Base class for services that can implement startUp(), run() and shutDown() methods. This class uses a single thread to execute the service; consider AbstractService if you would like to manage any threading manually.
Service.Listener, Service.State| Modifier | Constructor and Description |
|---|---|
protected |
AbstractExecutionThreadService()
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 Executor |
executor()
Returns the
Executor that will be used to run this service. |
Throwable |
failureCause()
Returns the
Throwable that caused this service to fail. |
boolean |
isRunning()
Returns
true if this service is running. |
protected abstract void |
run()
Run the service.
|
protected String |
serviceName()
Returns the name of this service.
|
protected void |
shutDown()
Stop the service.
|
Service |
startAsync()
If the service state is
Service.State.NEW, this initiates service startup and returns immediately. |
protected void |
startUp()
Start the service.
|
Service.State |
state()
Returns the lifecycle state of the service.
|
Service |
stopAsync()
|
String |
toString() |
protected void |
triggerShutdown()
Invoked to request the service to stop.
|
protected AbstractExecutionThreadService()
Constructor for use by subclasses.
protected void startUp()
throws Exception
Start the service. This method is invoked on the execution thread.
By default this method does nothing.
Exceptionprotected abstract void run()
throws Exception
Run the service. This method is invoked on the execution thread. Implementations must respond to stop requests. You could poll for lifecycle changes in a work loop:
public void run() { while (isRunning()) { // perform a unit of work } } …or you could respond to stop requests by implementing triggerShutdown(), which should cause run() to return.Exceptionprotected void shutDown()
throws Exception
Stop the service. This method is invoked on the execution thread.
By default this method does nothing.
Exceptionprotected void triggerShutdown()
Invoked to request the service to stop.
By default this method does nothing.
protected Executor executor()
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 should return promptly.
The default implementation returns a new Executor that sets the name of its threads to the string returned by serviceName()
public final boolean isRunning()
ServiceReturns true if this service is running.
public final Service.State state()
ServiceReturns the lifecycle state of the service.
public final void addListener(Service.Listener listener, Executor executor)
ServiceRegisters 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.
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 Servicelistener - 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 final Throwable failureCause()
ServiceReturns the Throwable that caused this service to fail.
failureCause in interface Servicepublic final Service startAsync()
ServiceIf the service state is Service.State.NEW, this initiates service startup and returns immediately. A stopped service may not be restarted.
startAsync in interface Servicepublic final Service stopAsync()
ServiceIf 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.
public final void awaitRunning()
ServiceWaits for the Service to reach the running state.
awaitRunning in interface Servicepublic final void awaitRunning(long timeout,
TimeUnit unit)
throws TimeoutException
ServiceWaits for the Service to reach the running state for no more than the given time.
awaitRunning in interface Servicetimeout - 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()
ServiceWaits for the Service to reach the terminated state.
awaitTerminated in interface Servicepublic final void awaitTerminated(long timeout,
TimeUnit unit)
throws TimeoutException
ServiceWaits for the Service to reach a terminal state (either terminated or failed) for no more than the given time.
awaitTerminated in interface Servicetimeout - the maximum time to waitunit - the time unit of the timeout argumentTimeoutException - if the service has not reached the given state within the deadlineprotected String serviceName()
Returns the name of this service. AbstractExecutionThreadService may include the name in debugging output.
Subclasses may override this method.