org.glassfish.jersey.spi

Class AbstractThreadPoolProvider<E extends ThreadPoolExecutor>

java.lang.Object

org.glassfish.jersey.spi.AbstractThreadPoolProvider<E>

All Implemented Interfaces:

AutoCloseable

Direct Known Subclasses:

ScheduledThreadPoolExecutorProvider, ThreadPoolExecutorProvider

public abstract class AbstractThreadPoolProvider<E extends ThreadPoolExecutor>
extends Object
implements AutoCloseable

Abstract thread pool executor provider.

This class provides a skeleton implementation for provisioning and basic lifecycle management of thread pool executors. Every instance of the concrete implementation of this provider class creates at most one shared and lazily initialized thread pool executor instance, which can be retrieved by invoking the getExecutor() method. This provider also makes sure that the provisioned thread pool executor instance is properly shut down when the managing provider instance is closed (in case it has not been already shut down).

At minimum, concrete subclasses of this provider are expected to implement the createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler) method that is used as a thread pool instance factory. The method is invoked lazily, with the first call to the getExecutor() method. The result returned from the createExecutor() method is cached internally and is used as a return value for subsequent calls to the getExecutor() method. This means, that createExecutor() method is guaranteed to be invoked at most once during the lifetime of any particular provider instance.

Since:

2.18

Author:

Marek Potociar

Field Summary

Fields

Modifier and Type	Field and Description
static int	DEFAULT_TERMINATION_TIMEOUT Default thread pool executor termination timeout in milliseconds.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractThreadPoolProvider(String name) Inheritance constructor.

Method Summary

Modifier and Type	Method and Description
void	close() Close this thread pool executor provider.
protected abstract E	createExecutor(int corePoolSize, ThreadFactory threadFactory, RejectedExecutionHandler handler) Create a new instance of the thread pool executor that should be provided by the getExecutor() method.
protected ThreadFactory	getBackingThreadFactory() Get a backing thread factory that should be used as a delegate for creating the new threads for the provisioned executor service.
protected int	getCorePoolSize() Get the number of the core threads of the the provisioned thread pool executor.
protected E	getExecutor() Get the thread pool executor.
protected RejectedExecutionHandler	getRejectedExecutionHandler() Get the handler for tasks that could not be executed by the provisioned thread pool executor.
protected int	getTerminationTimeout() Get the provisioned thread pool executor termination time out (in milliseconds).
boolean	isClosed() Check if this thread pool executor provider has been closed.
protected void	onClose() Close event handler, that invoked during the close() operation.

Methods inherited from class java.lang.Object

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

Field Detail

DEFAULT_TERMINATION_TIMEOUT

public static final int DEFAULT_TERMINATION_TIMEOUT

Default thread pool executor termination timeout in milliseconds.

See Also:

Constant Field Values

Constructor Detail

AbstractThreadPoolProvider

protected AbstractThreadPoolProvider(String name)

Inheritance constructor.

Parameters:

name - name of the provided thread pool executor. Will be used in the names of threads created & used by the provided thread pool executor.

Method Detail

getExecutor

protected final E getExecutor()

Get the thread pool executor.

The first invocation of this method will invoke the overridden createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler) method to retrieve the provided thread pool executor instance. The created thread pool executor instance is then cached and will be returned upon subsequent calls to this method.

Returns:

provided thread pool executor.

Throws:

IllegalStateException - in case the provider has been closed already.

See Also:

createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler), close(), isClosed()

createExecutor

protected abstract E createExecutor(int corePoolSize,
                                    ThreadFactory threadFactory,
                                    RejectedExecutionHandler handler)

Create a new instance of the thread pool executor that should be provided by the getExecutor() method.

Concrete implementations of this class must override this method and implement the logic that creates the executor service to be provided. The returned thread pool executor will be shut down when this provider instance is closed.

This method is invoked at most once, during the first call to the getExecutor() method.

Parameters:

corePoolSize - number of core threads the provisioned thread pool executor should provide.

threadFactory - thread factory to be used by the provisioned thread pool executor when creating new threads.

handler - handler for tasks that cannot be executed by the provisioned thread pool executor (e.g. due to a shutdown).

Returns:

new instance of the provided thread pool executor.

See Also:

getExecutor(), close(), getCorePoolSize(), getBackingThreadFactory(), getRejectedExecutionHandler()

getTerminationTimeout

protected int getTerminationTimeout()

Get the provisioned thread pool executor termination time out (in milliseconds).

The method is used during the thread pool executor shutdown sequence to determine the shutdown timeout, when this provider instance is closed. In case the thread pool executor shutdown is interrupted or the timeout expires, the provisioned thread pool executor is shutdown forcefully.

The method can be overridden to customize the thread pool executor termination time out. If not customized, the method defaults to 5000 ms.

Returns:

provisioned thread pool executor termination time out (in milliseconds).

See Also:

close(), ExecutorService.awaitTermination(long, java.util.concurrent.TimeUnit)

getCorePoolSize

protected int getCorePoolSize()

Get the number of the core threads of the the provisioned thread pool executor.

The value from this method is passed as one of the input parameters in a call to the createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler) method.

The method can be overridden to customize the number of core threads of the provisioned thread pool executor. If not customized, the method defaults to the number of available processors in the system.

Returns:

number of core threads in the provisioned thread pool executor.

See Also:

createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler)

getRejectedExecutionHandler

protected RejectedExecutionHandler getRejectedExecutionHandler()

Get the handler for tasks that could not be executed by the provisioned thread pool executor.

The value from this method is passed as one of the input parameters in a call to the createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler) method.

The method can be overridden to customize the rejected task handler used by the provisioned thread pool executor. If not customized, the method provides a basic default NO-OP implementation.

Returns:

handler for tasks that could not be executed by the provisioned thread pool executor.

See Also:

createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler)

getBackingThreadFactory

protected ThreadFactory getBackingThreadFactory()

Get a backing thread factory that should be used as a delegate for creating the new threads for the provisioned executor service.

The value from this method is used as a backing ThreadFactory for an internally constructed thread factory instance that is passed as one of the input parameters in a call to the createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler) method. When not null, the new threads will be created by invoking the ThreadFactory.newThread(Runnable) on this backing ThreadFactory.

The method can be overridden to customize the backing thread factory for the provisioned thread pool executor. If not customized, the method returns null by default.

Returns:

backing thread factory for the provisioned thread pool executor. May return null, in which case no backing thread factory will be used.

See Also:

createExecutor(int, java.util.concurrent.ThreadFactory, java.util.concurrent.RejectedExecutionHandler)

isClosed

public final boolean isClosed()

Check if this thread pool executor provider has been closed.

Returns:

true if this provider has been closed, false otherwise.

See Also:

close()

onClose

protected void onClose()

Close event handler, that invoked during the close() operation.

Concrete implementations of this provider class may override this method to perform any additional resource clean-up. Default implementation is a NO-OP.

See Also:

close()

close

public final void close()

Close this thread pool executor provider.

Once the provider is closed, it will stop providing the thread pool executor and subsequent invocations to getExecutor() method will result in an IllegalStateException being thrown. The current status of the provider can be checked via isClosed() method.

Upon invocation, the following tasks are performed:

• The thread pool executor instance provisioning via getExecutor() method is stopped.
• The onClose() event handler is invoked.
• The thread pool executor, if previously created and provisioned, is shut down.

The actual thread pool executor shutdown is performed as follows:

First, a graceful shutdown is attempted. The value returned from a call to getTerminationTimeout() method is used to determine the graceful shutdown timeout period.

In case the thread pool executor graceful shutdown is interrupted or the timeout expires, the provisioned thread pool executor is shutdown forcefully. All tasks that have never commenced execution are then cancelled interruptingly, if possible.

Specified by:

close in interface AutoCloseable

See Also:

isClosed(), onClose(), getExecutor(), getTerminationTimeout()