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package org.glassfish.jersey.spi;
import java.util.concurrent.ExecutorService;
/**
* An extension contract for providing pluggable executor service providers to be used by
* Jersey client or server runtime whenever a specific executor service is needed to execute a Jersey runtime processing task.
* <p>
* This mechanism allows Jersey to run in environments that have specific thread management and provisioning requirements,
* such as application servers, cloud environments etc.
* Dedicated Jersey extension modules or applications running in such environment may provide a custom
* implementation of the {@code ExecutorServiceProvider} interface to customize the default
* Jersey runtime thread management & provisioning strategy in order to comply with the threading requirements,
* models and policies specific to each particular environment.
* </p>
* <p>
* When Jersey runtime no longer requires the use of a provided executor service instance, it invokes the provider's
* {@link #dispose} method to signal the provider that the executor service instance can be disposed of. In this method,
* provider is free to implement the proper shut-down logic for the disposed executor service instance and perform other
* necessary cleanup. Yet, some providers may wish to implement a shared executor service strategy. In such case,
* it may not be desirable to shut down the released executor service in the {@link #dispose} method. Instead, to perform the
* eventual shut-down procedure, the provider may either rely on an explicit invocation of it's specific clean-up method.
* Since all Jersey providers operate in a <em>container</em> environment, a good clean-up strategy for a shared executor
* service provider implementation is to expose a {@link javax.annotation.PreDestroy @PreDestroy}-annotated method
* that will be invoked for all instances managed by the container, before the container shuts down.
* </p>
* <p>
* IMPORTANT: Please note that any pre-destroy methods may not be invoked for instances created outside of the container
* and later registered within the container. Pre-destroy methods are only guaranteed to be invoked for those instances
* that are created and managed by the container.
* </p>
* <p>
* Jersey runtime expects that a concrete executor service provider implementation class is annotated with a
* {@link javax.inject.Qualifier qualifier} annotation. This qualifier is then used to createAndInitialize a qualified injection point
* for injecting the executor service instance provided by the annotated provider. {@link javax.inject.Named Named} providers
* are also supported. For example:
* </p>
* <pre>
* @Named("my-executor")
* public MyExecutorProvider implements ExecutorServiceProvider {
* ...
* }
*
* ...
*
* // Injecting ExecutorService provided by the MyExecutorProvider
* @Inject @Named("my-executor") ExecutorService myExecutor;
* </pre>
*
* @author Marek Potociar (marek.potociar at oracle.com)
* @see ScheduledExecutorServiceProvider
* @see ThreadPoolExecutorProvider
* @since 2.18
*/
@Contract
public interface ExecutorServiceProvider {
/**
* Get an executor service to be used by Jersey client or server runtime to execute specific tasks.
* <p>
* This method is <em>usually</em> invoked just once at either Jersey client or server application runtime initialization,
* it <em>may</em> however be invoked multiple times. Once the instance of the provided executor service is not
* needed anymore by Jersey application runtime, it will be {@link #dispose disposed}.
* This typically happens in one of the following situations:
* </p>
* <ul>
* <li>Jersey client instance is closed (client runtime is shut down).</li>
* <li>Jersey container running a server-side Jersey application is shut down.</li>
* <li>Jersey server-side application is un-deployed.</li>
* </ul>
*
* @return an executor service. Must not return {@code null}.
*/
public ExecutorService getExecutorService();
/**
* Invoked when Jersey runtime no longer requires use of the provided executor service.
*
* @param executorService executor service to be disposed.
*/
public void dispose(ExecutorService executorService);
}