javax.enterprise.concurrent.ManagedExecutorService Maven / Gradle / Ivy
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package javax.enterprise.concurrent;
import java.util.concurrent.ExecutorService;
/**
* 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 Java™ EE environment.
* Implementations of the ManagedExecutorService are
* provided by a Java™ 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 Concurrency Utilities for Java™ EE 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 Enterprise
* JavaBean™ (EJB™) or for processing async tasks for Servlets that
* supports asynchronous processing.
*
* Tasks are run in managed threads provided by the Java™ 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
* {@link javax.transaction.UserTransaction} instance. A UserTransaction instance is
* available in JNDI using the name: "java:comp/UserTransaction" or by
* requesting an injection of a {@link javax.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 an {@link ManagedTaskListener} to receive
* notifications of lifecycle events, through the use of {@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: javax.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...
* }
*
*
*
* @since 1.0
*/
public interface ManagedExecutorService extends ExecutorService {
}