AbstractService (Guava: Google Core Libraries for Java 14.0.1 API)

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.

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.
`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()` 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.
`String`	`toString()`

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.
  - 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.
  - 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.
  - 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.
  - 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 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()
```
    Overrides:
    
    toString in class Object

Class AbstractService

Nested Class Summary

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

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

AbstractService

Method Detail

doStart

doStop

start

stop

startAndWait

stopAndWait

notifyStarted

notifyStopped

notifyFailed

isRunning

state

failureCause

addListener

toString