AbstractService (Guava: Google Core Libraries for Java 28.1-jre API)

java.lang.Object
- com.google.common.util.concurrent.AbstractService

All Implemented Interfaces:

Service
```
@Beta
 @GwtIncompatible
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

All Methods Instance Methods Abstract Methods Concrete 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 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()` 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

Methods inherited from interface com.google.common.util.concurrent.Service
awaitRunning, awaitTerminated

- Constructor Detail
  - AbstractService
```
protected AbstractService()
```
    Constructor for use by subclasses.
- Method Detail
  - doStart
```
@ForOverride
protected abstract void doStart()
```
    This method is called by 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.
  - doStop
```
@ForOverride
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 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}.
  - doCancelStart
```
@ForOverride
protected void doCancelStart()
```
    This method is called by 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().
    
    Since:
    
    27.0
  - startAsync
```
@CanIgnoreReturnValue
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
  - stopAsync
```
@CanIgnoreReturnValue
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
  - 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.STARTING or Service.State.STOPPING to Service.State.TERMINATED.
    
    Throws:
    
    IllegalStateException - if the service is not one of Service.State.STOPPING, Service.State.STARTING, or 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.
    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.
    
    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.directExecutor().
    
    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.

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

Methods inherited from interface com.google.common.util.concurrent.Service

Constructor Detail

AbstractService

Method Detail

doStart

doStop

doCancelStart

startAsync

stopAsync

awaitRunning

awaitRunning

awaitTerminated

awaitTerminated

notifyStarted

notifyStopped

notifyFailed

isRunning

state

failureCause

addListener

toString