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Copyright © 2013 Oracle and/or its affiliates. All rights reserved.
JSR 236: Concurrency
Utilities for Java EE
Applications
Shing Wai Chan (陳成威)
Anissa Lam (梁鈺儀）
Session ID: CON1468
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Program Agenda
 Overview
 Managed Objects
 Context & Transaction
 Summary
 Resources
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Overview
 New to Java EE 7
 Simple, standardized API for using concurrency from application
components
 Extension of Java SE Concurrency Utilities APIs (JSR-166)
 Low-level asynchronous processing capabilities to Java EE application
components in a safe, reliable, consistent manner
 Manage and monitor the lifecycle of asynchronous operations
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Overview
 Provides 4 types of managed objects that implement these interfaces
– ManagedExecutorService
– ManagedScheduledExecutorService
– ManagedThreadFactory
– ContextService
 Context propagation
 Transaction Management
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Overview
 Managed Objects are provided by the Java EE Product Provider
 Pre-configured default object is available
 Applications look up managed objects by
– JNDI lookup
– resource injection using @Resource
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Program Agenda
 Overview
 Managed Objects
 Context & Transaction
 Summary
 Resources
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Copyright © 2013 Oracle and/or its affiliates. All rights reserved.
ManagedExecutorService
Overview
 For running tasks asynchronously on threads provided by Java EE
product provider
 Container context captured from submitting thread to be applied on
execution thread
 Not transactional – tasks should use their own transactions
 Preconfigured default:
– java:comp/DefaultManagedExecutorService
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ManagedExecutorService
API
 Extends from java.util.concurrent.ExecutorService
– execute, submit, invokeAll, invokeAny
– No new APIs
 Lifecycle APIs disabled – throws IllegalStateException
awaitTermination, isTerminated, isShutdown, shutdown,
shutdownNow
 Future is returned upon task submission
– check for the execution status
– cancel the task
– Wait and retrieve result
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ManagedExecutorService
API
void execute(Runnable command);
<T> Future<T> submit(Callable<T> task);
Future<?> submit(Runnable task);
<T> Future<T> submit(Runnable task, T result);
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks);
<T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks,
long timeout, TimeUnit unit);
<T> T invokeAny(Collection<? extends Callable<T>> tasks)
<T> T invokeAny(Collection<? extends Callable<T>> tasks, long timeout,
TimeUnit unit);
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ManagedExecutorService
Example #1
@Resource(name=“concurrent/myExecutor”)
ManagedExecutorService mes;
void someMethod() {
Callable<Integer> c = new Callable<>() {
Integer call() {
// Interact with a database...return answer.
}
//Submit the task and do something else.
Future result = mes.submit(c);
...
//Get the result when ready...
int theValue = result.get();
...
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ManagedExecutorService
Example #2
// Retrieve all accounts from several account databases in parallel.
//JNDI Lookup
javax.naming.InitialContext ctx = new InitialContext();
ManagedExecutorService mes = (ManagedExecutorService)
ctx.lookup("java:comp/DefaultManagedExecutorService");
// 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 completion.
List<Future<Account>> taskResults= mes.invokeAll(retrieverTasks);
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ManagedExecutorService
Example #2 (cont’d)
// 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();
}
}
return results;
public class EISAccountRetriever implements Callable<Account> {
public Account call() { … }
}
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ManagedExecutorService
Configuration
 Choose a more simplistic approach
 add more functionality such as Quality-of-service, Persistence or Task
partitioning etc.
 Possible options: (as in GlassFish 4.0)
– JNDI Name
– Context Info
– Thread Priority
– Hung Task Threshold
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ManagedExecutorService
Configuration (cont’d)
 Configuration of the underlying thread pool.
– Core size
– Maximum Pool Size
– Thread Lifetime
– Keep Alive
– Task Queue Capacity
 Cached thread pool as described in
java.util.concurrent.Executors will be created when no
attribute is specified.
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ManagedExecutorService
Managed Thread Pool Executor Component Relationship
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ManagedScheduledExecutorService
Overview
 For scheduling tasks to run on threads
– after a given delay,
– run periodically
– at some custom schedule
 tasks are also run on threads that are provided by the Java EE
container.
 Preconfigured default:
 java:comp/DefaultManagedScheduledExecutorService
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ManagedScheduledExecutorService
API
 Extends from
– ManagedExecutorService
– java.util.concurrent.ScheduledExecutorService
 APIs in addition to ManagedExecutorService
– schedule
– scheduleAtFixedRate
– scheduleWithFixedDelay
 Extension API to support custom scheduling
– schedule with Trigger
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ManagedScheduledExecutorService
API
<V> ScheduledFuture<V> schedule(Callable<V> callable, long delay,
TimeUnit unit);
ScheduledFuture<?> schedule(Runnable command, long delay,
TimeUnit unit);
ScheduledFuture<?> scheduleAtFixedFate(Runnable command,
long initialDelay, long period, TimeUnit unit);
ScheduledFuture<?> scheduledWithFixedDelay(Runnable command,
long initialDelay, long delay, TimeUnit unit);
ScheduledFuture<?> schedule(Runnable command, Trigger trigger);
<V> ScheduledFuture<V> schedule(Callable<V> callable, Trigger trigger);
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ManagedScheduledExecutorService
Configuration
 In GlassFish 4.0, same configuration as in
ManagedExecutorService except for
– Task Queue Capacity
– Maximum Pool Size
 Reason: a fixed-size pool with an unbounded queue are always used
in ManagedScheduledExecutorService.
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ManagedScheduledExecutorService
Trigger
 Allows application developer to plugin rules for running a task.
 Can be simple: single, absolute date-time
 Can include Java™ EE business calendar logic
 Registered with a task when it is submitted
 Invoked within the same process in which it was registered.
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ManagedScheduledExecutorService
Trigger API
boolean skipRun(LastExecution lastExecutionInfo,
Date scheduledRunTime)
Date getNextRunTime(LastExecution
lastExecutionInfo, Date taskScheduledTime)
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ManagedScheduledExecutorService
Trigger Example
public class SingleDateTrigger implements Trigger {
private Date fireTime;
public TriggerSingleDate(Date newDate) {
fireTime = newDate;
}
public Date getNextRunTime(
LastExecution lastExecutionInfo, Date taskScheduledTime) {
if(taskScheduledTime.after(fireTime)) {
return null;
}
return fireTime;
}
public boolean skipRun(LastExecution lastExecutionInfo, Date
scheduledRunTime) {
return scheduledRunTime.after(fireTime);
}
}
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ManagedExecutors
 Utilities for classes defined in javax.enterprise.concurrent
 Tests if current thread is a ManageableThread
 Tests if current thread has been marked for shutdown
 #managedTask
– Returns a Callable/Runnable that also implements ManagedTask
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ManagedExecutors
API
 public static boolean isCurrentThreadShutdown()
 public static Runnable managedTask(Runnable task,
ManagedTaskListener taskListener) throws IllegalArgumentException
 public static Runnable managedTask(Runnable task, Map<String,String>
executionProperties, ManagedTaskListener taskListener) throws
IllegalArgumentException
 public static <V> Callable<V> managedTask(Callable<V> task,
ManagedTaskListener taskListener) throws IllegalArgumentException
 public static <V> Callable<V> managedTask(Callable<V> task,
Map<String,String> executionProperties, ManagedTaskListener
taskListener) throws IllegalArgumentException
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Managed[Scheduled]ExecutorService
ManagedTask
 Any task submitted to an Managed[Scheduled]ExecutorService
can optionally implement ManagedTask
 Provides
– Identifying information
– ManagedTaskListener for lifecycle events notification
– Additional execution properties
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Managed[Scheduled]ExecutorService
ManagedTask
 API
– Map<String, String> getExecutionProperties()
– ManagedTaskListener getManagedTaskListener()
 Execution properties
– LONGRUNNING_HINT
– IDENTITY_NAME
– TRANSACTION
 SUSPEND
 USE_TRANSACTION_OF_EXECUTION_THREAD
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Managed[Scheduled]ExecutorService
ManagedTaskListener
 Monitor the state of a task’s Future
 Registered with a ManagedExecutorService using submit
 Invoked when the state of Future changes
 Each instance is invoked within same process that the listener was
registered
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Managed[Scheduled]ExecutorService
ManagedTaskListener API
 void taskSubmitted(Future<?> future,
ManagedExecutorService executor, Object task)
 void taskDone(Future<?> future,
ManagedExecutorService executor, Object task,
Throwable exception)
 void taskStarting(Future<?> future,
ManagedExecutorService executor, Object task)
 void taskSubmitted(Future<?> future,
ManagedExecutorService executor, Object task)
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Managed[Scheduled]ExecutorService
Example: Registering ManagedTaskListener
// Runnable implements ManagedTask
public class TaskWithListener implements Runnable, ManagedTask {
...
public ManagedTaskListener getManagedTaskListener() {
return aManagedTaskListener;
}
}
//use ManagedExecutors utility to associate a ManagedTaskListener to a task
Runnable aTask;
ManagedTaskListener myTaskListner;
Runnable taskWithListener =
ManagedExecutors.managedTask(aTask, myTaskListener);
...
ManagedExecutorService executor = ...;
executor.submit(task);
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ManagedThreadFactory
Overview
 A standard way for applications to obtain a container-managed
threads from Java EE Container
 Container context captured at newThread call to be applied to
thread that invokes r.run()
 For creating custom executors in advanced use cases
 Preconfigured default:
– java:comp/DefaultManagedThreadFactory
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ManagedThreadFactory
Sample Configuration
 JNDI Name
 Context Info
– Classloader
– JNDI
– Security
 Priority
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ManagedThreadFactory
API
 Interface extends from java.util.concurrent.ThreadFactory
– Same API:
Thread newThread(Runnable)
 Threads returned by newThread() method must implement the
ManagableThread interface
– boolean isShutdown()
 Can be used with Java SE concurrency utilities APIs where
ThreadFactory is needed. e.g. in
java.util.concurrent.Executors
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ManagedThreadFactory
Shutdown
 Thread interrupted when ManagedThreadFactory shuts down
 Runnable should check ManagableThread.isShutdown() when
interrupted, and clean up if it is true.
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ManagedThreadFactory
Example 1
// Create a ThreadPoolExecutor using a ManagedThreadFactory.
@Resource(lookup=“java:comp/DefaultThreadFactory”)
ManagedThreadFactory tf;
public ExecutorService getManagedThreadPool() {
// All threads will run as part of this application component.
return new ThreadPoolExecutor(5, 10, 5, TimeUnit.SECONDS,
new ArrayBlockingQueue<Runnable>(10), tf);
}
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ManagedThreadFactory
Example 2 (with Servlet Asynchronous mode)
public class TestServlet extends HttpServlet {
@Resource(lookup=“java:comp/DefaultManagedFactory”)
private ManagedThreadFactory managedThreadFactory;
protected void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException {
final AsyncContext asyncContext = req.startAsync();
…
Runnable runnable = new Runnable() {
public void run() {
…
asyncContext.complete();
}
};
Thread thread = managedThreadFactory.newThread(runnable);
thread.start();
}
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}
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ContextService
Overview
 For creating contextual proxy objects to capture container context to
be run within the captured context at a later time
 For use in advanced use cases such as to propagate user identity
or to request task listener notifications to be run under container
context
 Contextual proxy objects can also be used as tasks for submission
to Managed[Scheduled]ExecutorService or
ManagedThreadFactory
 Preconfigured default:
– java:comp/DefaultContextService
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ContextService
Sample Configuration
 JNDI Name
 Context Info
– Classloader
– JNDI
– Security
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ContextService
API
 Interface
 Creating dynamic proxy (as in java.lang.reflect.Proxy)
 With additional context such as class loading, namespace, security,
etc.
 The instance must implement Serializable if the proxy is serialized
 Execution properties, Map<String, String>
– reserved keys: started with “javax.enterprise.concurrent.”
– E.g. vendor.security.tokenexpiration
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ContextService
API (cont’d)
 Four createContextualProxy methods:
– <T> T createContextualProxy(T instance, Class<T> intf)
– <T> T createContextualProxy(T instance,
Map<String,String> executionProperties, Class<T> intf)
– Object createContextualProxy(Object instance,
Map<String,String> executionProperties, Class<?>...
Interfaces)
– Object createContextualProxy(Object instance,
Class<?>... Interfaces)
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ContextService
API (cont’d 2)
 For returning the execution properties on the given contextual object
proxy instance
– Map<String,String> getExecutionProperties(Object
contextualProxy)
– IllegalArgumentException: if contextualProxy is not a valid proxy
object created with #createContextualProxy of this ContextService
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ContextService
Example 1
@Resource ContextService ctxSvc;
MyAppIntf proxy =
ctxSvc.createContextualProxy (myAppImpl, MyAppIntf.class);
// invoke at a later time, possibly in a different app
// component
proxy.doSomething();
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ContextService
Example 2
// In application
public interface MessageProcessor {
public void processMessage(Message msg)
…
}
// Within servlet or EJB method…
@Resource ContextService ctxSvc;
void businessMethod() {
MessageProcessor msgProcessor = …
// Wrap with the current context
MessageProcessor proxy = ctxSvc.createContextualProxy
(msgProcessor, MessageProcessor.class);
// Store the contextual proxy object somewhere for running later.
store.putIt(proxy);
…
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ContextService
Example 2 (cont’d)
// Elsewhere, in a different thread, retrieve the MessageProcessor contextual proxy
// object from the store
MessageProcessor proxy = store.getIt();
// The proxy method processMessage() is invoked on
// this thread, but with the context of the servlet or
// EJB that created it.
proxy.processMessage(msg);
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ContextService
Example 3 (Serialization in a web application)
public class MyWork implements Callable<Void>, Serializable { … }
// in Servlet A
Callable mywork = contextService.createContextualProxy(new
MyWork(), Callable.class);
try (ObjectOutputStream oos = …) {
oos.writeObject(mywork);
}
// in Servlet B
try (ObjectInputStream ois = …) {
myWork = (Callable)ois.readObject();
managedExecutorService.submit(myWork);
…
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Program Agenda
 Overview
 Managed Objects
 Context & Transaction
 Summary
 Resources
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Context & Transaction
Context Propagation
 Types of container context:
– Class loading, JNDI namespace, security identity
– Configurable, extensible
 Container context captured to be applied on execution thread, and
to be applied on proxy invocation time.
 Supported in all 4 types of managed objects
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Context & Transaction
Transaction Management
 Transaction are typically not propagated to the execution tasks
 UserTransaction from JTA is available
 Contextual proxy objects from ContextService can be run on
the same transaction context of the invoking thread
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Context & Transaction
Example
@Resource(lookup=“java:comp/DefaultContextService”)
private ContextService cx;
@Resource(lookup=“java:comp/UserTransaction”)
private UserTransaction ut;
…
ut.begin();
…
MyWork proxy = cx.createContextualProxy(work, map, MyWork.class);
…
ut.commit();
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Copyright © 2013 Oracle and/or its affiliates. All rights reserved.
Program Agenda
 Overview
 Managed Objects
 Context & Transaction
 Summary
 Resources
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Summary
 Provides asynchronous capabilities to Java EE application
components
 Allows Java SE developers simple migration path to Java EE
 Provides managed objects to applications for submitting tasks and
obtaining managed threads
 Features such as propagation of container context
 Java EE application developers now have tools to have more
advanced control of asynchronous processing.
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Program Agenda
 Overview
 Managed Objects
 Context & Transaction
 Summary
 Resources
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Resources
 Spec and API docs
– http://jcp.org/en/jsr/detail?id=236
– http://concurrency-ee-spec.java.net/javadoc
 Java EE 7 SDK
– http://www.oracle.com/javaee
 GlassFish 4.0
– http://glassfish.java.net/
 Reference Implementation
– http://java.net/projects/cu-javaee
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