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/*
* Copyright (c) 2010, 2021 Oracle and/or its affiliates. All rights reserved.
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v. 2.0, which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the
* Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
* version 2 with the GNU Classpath Exception, which is available at
* https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
*/
package jakarta.enterprise.concurrent;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.CompletionStage;
import java.util.concurrent.ExecutorService;
import java.util.function.Supplier;
/**
* A manageable version of a {@link java.util.concurrent.ExecutorService}.
*
* A ManagedExecutorService extends the Java™ SE ExecutorService to provide
* methods for submitting tasks for execution in a Jakarta™ EE environment.
* Implementations of the ManagedExecutorService are
* provided by a Jakarta EE Product Provider. Application Component Providers
* use the Java Naming and Directory Interface™ (JNDI) to look-up instances of one
* or more ManagedExecutorService objects using resource environment references.
* ManagedExecutorService instances can also be injected into application
* components through the use of the {@code Resource} annotation.
*
* The Jakarta Concurrency specification describes several
* behaviors that a ManagedExecutorService can implement. The Application
* Component Provider and Deployer identify these requirements and map the
* resource environment reference appropriately.
*
* The most common uses for a ManagedExecutorService is to run short-duration asynchronous
* tasks such as for processing of asynchronous methods in Jakarta
* Enterprise Beans or for processing async tasks for Servlets that
* supports asynchronous processing.
*
* Tasks are run in managed threads provided by the Jakarta EE Product Provider
* and are run within the application component context that submitted the task.
* All tasks run without an explicit transaction (they do not enlist in the application
* component's transaction). If a transaction is required, use a
* {@code jakarta.transaction.UserTransaction} instance. A UserTransaction instance is
* available in JNDI using the name: "java:comp/UserTransaction" or by
* requesting an injection of a {@code jakarta.transaction.UserTransaction} object
* using the {@code Resource} annotation.
*
* Example:
*
* public run() {
* // Begin of task
* InitialContext ctx = new InitialContext();
* UserTransaction ut = (UserTransaction) ctx.lookup("java:comp/UserTransaction");
* ut.begin();
*
* // Perform transactional business logic
*
* ut.commit();
* }
*
*
* Tasks can optionally provide a {@link ManagedTaskListener} to receive
* notifications of lifecycle events, through the use of the {@link ManagedTask}
* interface.
*
* Example:
*
* public class MyRunnable implements Runnable, ManagedTask {
* ...
* public void run() {
* ...
* }
*
* public ManagedTaskListener getManagedTaskListener() {
* return myManagedTaskListener;
* }
* ...
* }
*
* MyRunnable task = ...;
* ManagedExecutorService executor = ...;
*
* executor.submit(task); // lifecycle events will be notified to myManagedTaskListener
*
*
* Asynchronous tasks are typically submitted to the ManagedExecutorService using one
* of the {@code submit} methods, each of which return a {@link java.util.concurrent.Future}
* instance. The {@code Future} represents the result of the task and can also be used to
* check if the task is complete or wait for its completion.
*
*
* If the task is canceled, the result for the task is a
* {@link java.util.concurrent.CancellationException} exception. If the task is unable
* to run due to a reason other than cancellation, the result is a
* {@link AbortedException} exception.
*
*
*Example:
*
* /**
* * Retrieve all accounts from several account databases in parallel.
* * Resource Mappings:
* * type: jakarta.enterprise.concurrent.ManagedExecutorService
* * jndi-name: concurrent/ThreadPool
* */
* public List<Account> getAccounts(long accountId) {
* try {
* javax.naming.InitialContext ctx = new InitialContext();
* ManagedExecutorService mes = (ManagedExecutorService)
* ctx.lookup("java:comp/env/concurrent/ThreadPool");
*
* // Create a set of tasks to perform the account retrieval.
* ArrayList<Callable<Account>> retrieverTasks = new ArrayList<Callable<Account>>();
* retrieverTasks.add(new EISAccountRetriever());
* retrieverTasks.add(new RDBAccountRetriever());
*
* // Submit the tasks to the thread pool and wait for them
* // to complete (successfully or otherwise).
* List<Future<Account>> taskResults= mes.invokeAll(retrieverTasks);
*
* // Retrieve the results from the resulting Future list.
* ArrayList<Account> results = new ArrayList<Account>();
* for(Future<Account> taskResult : taskResults) {
* try {
* results.add(taskResult.get());
* } catch (ExecutionException e) {
* Throwable cause = e.getCause();
* // Handle the AccountRetrieverError.
* }
* }
*
* return results;
*
* } catch (NamingException e) {
* // Throw exception for fatal error.
* } catch (InterruptedException e) {
* // Throw exception for shutdown or other interrupt condition.
* }
* }
*
*
* public class EISAccountRetriever implements Callable<Account> {
* public Account call() {
* // Connect to our eis system and retrieve the info for the account.
* //...
* return null;
* }
* }
*
* public class RDBAccountRetriever implements Callable<Account> {
* public Account call() {
* // Connect to our database and retrieve the info for the account.
* //...
* }
* }
*
* public class Account {
* // Some account data...
* }
*
*
* ManagedExecutorService provides various methods which correspond to the
* static methods of {@link java.util.concurrent.CompletableFuture} and its
* constructor/newIncompleteFuture method,
* enabling you to create completion stages that are backed by the ManagedExecutorService
* as the default asynchronous execution facility, both for those stages
* as well as all dependent stages that are created from those, and so on.
* This allows you to create pipelines of completion stage actions that run
* with consistent and predictable thread context, regardless of which thread each
* dependent action ends up running on.
*
* Example:
*
* ManagedExectorService executor = InitialContext.doLookup("java:comp/DefaultManagedExecutorService");
* ...
* CompletableFuture<Integer> future = executor
* .supplyAsync(supplier)
* .thenApply(function1)
* .thenApplyAsync(function2)
* ...
*
*
*
* Context propagation to completion stages that are backed by a
* ManagedExecutorService must be done in a consistent
* and predictable manner, which is defined as follows,
*
*
* -
* If the supplied action is already contextual, (for example,
*
contextService.createContextualProxy(action, Runnable.class)),
* then the action runs with the already-captured context.
*
* -
* Otherwise, each type of thread context is either propagated from the thread
* that creates the completion stage or the context is marked to be cleared, according to the
* configuration of the
ManagedExecutorService that is the default asynchronous execution facility
* for the new stage and its parent stage. In the case that a ManagedExecutorService is supplied
* as the executor argument to a *Async method, the supplied
* ManagedExecutorService is used to run the action, but not to determine the thread context
* propagation and clearing.
*
*
*
* Each type of thread context is applied (either as cleared or previously captured)
* to the thread that runs the action. The applied thread context is removed after the action
* completes, whether successfully or exceptionally, restoring the thread's prior context.
*
* When dependent stages are created from the completion stage, and likewise from any dependent stages
* created from those, and so on, thread context is captured or cleared in the same manner.
* This guarantees that the action performed by each stage always runs under the thread context
* of the code that creates the completion stage, unless the user explicitly overrides this by supplying a
* pre-contextualized action.
*
* Completion stages that are backed by a ManagedExecutorService must raise
* {@link java.lang.IllegalArgumentException} if supplied with an action that implements
* {@link ManagedTask}.
*
* @since 1.0
*/
public interface ManagedExecutorService extends ExecutorService {
/**
* Returns a new {@link java.util.concurrent.CompletableFuture}
* that is already completed with the specified value.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param value result with which the completable future is completed.
* @param result type of the completable future.
* @return the new completable future.
* @since 3.0
*/
CompletableFuture completedFuture(U value);
/**
* Returns a new {@link java.util.concurrent.CompletionStage}
* that is already completed with the specified value.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param value result with which the completion stage is completed.
* @param result type of the completion stage.
* @return the new completion stage.
* @since 3.0
*/
CompletionStage completedStage(U value);
/**
*
* Returns a new {@link java.util.concurrent.CompletableFuture}
* that is completed by the completion of the
* specified stage.
*
*
*
* The new completable future is backed by the ManagedExecutorService upon which copy is invoked,
* which serves as the default asynchronous execution facility
* for the new stage and all dependent stages created from it, and so forth.
*
*
*
* When dependent stages are created from the new completable future, thread context is captured
* and/or cleared by the ManagedExecutorService. This guarantees that the action
* performed by each stage always runs under the thread context of the code that creates the stage,
* unless the user explicitly overrides by supplying a pre-contextualized action.
*
*
*
* Invocation of this method does not impact thread context propagation for the supplied
* completable future or any other dependent stages directly created from it.
*
*
* @param completable future result type.
* @param stage a completable future whose completion triggers completion of the new completable
* future that is created by this method.
* @return the new completable future.
* @since 3.0
*/
CompletableFuture copy(CompletableFuture stage);
/**
*
* Returns a new {@link java.util.concurrent.CompletionStage}
* that is completed by the completion of the
* specified stage.
*
*
*
* The new completion stage is backed by the ManagedExecutorService upon which copy is invoked,
* which serves as the default asynchronous execution facility
* for the new stage and all dependent stages created from it, and so forth.
*
*
*
* When dependent stages are created from the new completion stage, thread context is captured
* and/or cleared by the ManagedExecutorService. This guarantees that the action
* performed by each stage always runs under the thread context of the code that creates the stage,
* unless the user explicitly overrides by supplying a pre-contextualized action.
*
*
*
* Invocation of this method does not impact thread context propagation for the supplied
* stage or any other dependent stages directly created from it.
*
*
* @param completion stage result type.
* @param stage a completion stage whose completion triggers completion of the new stage
* that is created by this method.
* @return the new completion stage.
* @since 3.0
*/
CompletionStage copy(CompletionStage stage);
/**
* Returns a new {@link java.util.concurrent.CompletableFuture}
* that is already exceptionally completed with the specified Throwable.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param ex exception or error with which the completable future is completed.
* @param result type of the completable future.
* @return the new completable future.
* @since 3.0
*/
CompletableFuture failedFuture(Throwable ex);
/**
* Returns a new {@link java.util.concurrent.CompletionStage}
* that is already exceptionally completed with the specified Throwable.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param ex exception or error with which the completion stage is completed.
* @param result type of the completion stage.
* @return the new completion stage.
* @since 3.0
*/
CompletionStage failedStage(Throwable ex);
/**
* Returns a {@link ContextService} which has the same propagation settings as this ManagedExecutorService
* and uses this ManagedExecutorService as the default asynchronous execution facility for
* {@link java.util.concurrent.CompletionStage} and {@link java.util.concurrent.CompletableFuture} instances
* that it creates via the withContextCapture methods.
*
* @return a ContextService with the same propagation settings
* as this ManagedExecutorService.
* @since 3.0
*/
public ContextService getContextService();
/**
* Returns a new incomplete {@link java.util.concurrent.CompletableFuture}.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param result type of the completable future.
* @return the new completable future.
* @since 3.0
*/
CompletableFuture newIncompleteFuture();
/**
* Returns a new {@link java.util.concurrent.CompletableFuture}
* that is completed by a task running in this executor
* after it runs the given action.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param runnable the action to run before completing the returned completion stage.
* @return the new completable future.
* @since 3.0
*/
CompletableFuture runAsync(Runnable runnable);
/**
* Returns a new {@link java.util.concurrent.CompletableFuture}
* that is completed by a task running in this executor
* after it runs the given action.
*
* This executor is the default asynchronous execution facility for the new completion stage
* that is returned by this method and all dependent stages that are created from it,
* and all dependent stages that are created from those, as so forth.
*
* @param supplier an action returning the value to be used to complete the returned completion stage.
* @param result type of the supplier and returned completable stage.
* @return the new completable future.
* @since 3.0
*/
CompletableFuture supplyAsync(Supplier supplier);
}