latest/examples/async-methods.html - tomee-site-pub - Git at Google

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               <h1>@Asynchronous Methods</h1>
             </div>
           </div>
         </div>
         <div class="row">

             <div class="col-md-12">
                 <div id="preamble">
 <div class="sectionbody">
 <div class="paragraph">
 <p>The @Asynchronous annotation was introduced in EJB 3.1 as a simple way
 of creating asynchronous processing.</p>
 </div>
 <div class="paragraph">
 <p>Every time a method annotated <code>@Asynchronous</code> is invoked by anyone it
 will immediately return regardless of how long the method actually
 takes. Each invocation returns a
 <a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Future.html">Future</a>
 object that essentially starts out <em>empty</em> and will later have its value
 filled in by the container when the related method call actually
 completes. Returning a <code>Future</code> object is not required and
 <code>@Asynchronous</code> methods can of course return <code>void</code>.</p>
 </div>
 </div>
 </div>
 <div class="sect1">
 <h2 id="_example">Example</h2>
 <div class="sectionbody">
 <div class="paragraph">
 <p>Here, in <code>JobProcessorTest</code>,</p>
 </div>
 <div class="paragraph">
 <p><code>final Future&lt;String&gt; red = processor.addJob("red");</code> proceeds to the
 next statement,</p>
 </div>
 <div class="paragraph">
 <p><code>final Future&lt;String&gt; orange = processor.addJob("orange");</code></p>
 </div>
 <div class="paragraph">
 <p>without waiting for the <code>addJob()</code> method to complete. And later we could
 ask for the result using the <code>Future&lt;?&gt;.get()</code> method like</p>
 </div>
 <div class="paragraph">
 <p><code>assertEquals("blue", blue.get());</code></p>
 </div>
 <div class="paragraph">
 <p>It waits for the processing to complete (if its not completed already)
 and gets the result. If you did not care about the result, you could
 simply have your asynchronous method as a <code>void</code> method.</p>
 </div>
 <div class="paragraph">
 <p><a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Future.html">Future</a>
 Object from docs,</p>
 </div>
 <div class="quoteblock">
 <blockquote>
 <div class="paragraph">
 <p>A Future represents the result of an asynchronous computation. Methods
 are provided to check if the computation is complete, to wait for its
 completion, and to retrieve the result of the computation. The result
 can only be retrieved using method get when the computation has
 completed, blocking if necessary until it is ready. Cancellation is
 performed by the cancel method. Additional methods are provided to
 determine if the task completed normally or was cancelled. Once a
 computation has completed, the computation cannot be cancelled. If you
 would like to use a Future for the sake of cancellability but not
 provide a usable result, you can declare types of the form Future&lt;?&gt; and
 return null as a result of the underlying task</p>
 </div>
 </blockquote>
 </div>
 </div>
 </div>
 <div class="sect1">
 <h2 id="_the_code">The code</h2>
 <div class="sectionbody">
 <div class="listingblock">
 <div class="content">
 <pre class="highlight"><code class="language-java" data-lang="java">@Singleton
 public class JobProcessor {
 @Asynchronous
 @Lock(READ)
 @AccessTimeout(-1)
 public Future&lt;String&gt; addJob(String jobName) {

     // Pretend this job takes a while
     doSomeHeavyLifting();

     // Return our result
     return new AsyncResult&lt;String&gt;(jobName);
 }

 private void doSomeHeavyLifting() {
     try {
         Thread.sleep(SECONDS.toMillis(10));
     } catch (InterruptedException e) {
         Thread.interrupted();
         throw new IllegalStateException(e);
     }
   }
 }</code></pre>
 </div>
 </div>
 </div>
 </div>
 <div class="sect1">
 <h2 id="_test">Test</h2>
 <div class="sectionbody">
 <div class="listingblock">
 <div class="content">
 <pre class="highlight"><code class="language-java" data-lang="java">public class JobProcessorTest extends TestCase {

 public void test() throws Exception {

     final Context context = EJBContainer.createEJBContainer().getContext();

     final JobProcessor processor = (JobProcessor) context.lookup("java:global/async-methods/JobProcessor");

     final long start = System.nanoTime();

     // Queue up a bunch of work
     final Future&lt;String&gt; red = processor.addJob("red");
     final Future&lt;String&gt; orange = processor.addJob("orange");
     final Future&lt;String&gt; yellow = processor.addJob("yellow");
     final Future&lt;String&gt; green = processor.addJob("green");
     final Future&lt;String&gt; blue = processor.addJob("blue");
     final Future&lt;String&gt; violet = processor.addJob("violet");

     // Wait for the result -- 1 minute worth of work
     assertEquals("blue", blue.get());
     assertEquals("orange", orange.get());
     assertEquals("green", green.get());
     assertEquals("red", red.get());
     assertEquals("yellow", yellow.get());
     assertEquals("violet", violet.get());

     // How long did it take?
     final long total = TimeUnit.NANOSECONDS.toSeconds(System.nanoTime() - start);

     // Execution should be around 9 - 21 seconds
     // The execution time depends on the number of threads available for asynchronous execution.
     // In the best case it is 10s plus some minimal processing time.
     assertTrue("Expected &gt; 9 but was: " + total, total &gt; 9);
     assertTrue("Expected &lt; 21 but was: " + total, total &lt; 21);

   }
 }</code></pre>
 </div>
 </div>
 <div class="listingblock">
 <div class="content">
 <pre class="highlight"><code class="language-console" data-lang="console">-------------------------------------------------------
  T E S T S
 -------------------------------------------------------
 Running org.superbiz.async.JobProcessorTest
 INFO - ********************************************************************************
 INFO - OpenEJB http://tomee.apache.org/
 INFO - Startup: Wed Feb 27 12:46:11 BRT 2019
 INFO - Copyright 1999-2018 (C) Apache OpenEJB Project, All Rights Reserved.
 INFO - Version: 8.0.0-SNAPSHOT
 INFO - Build date: 20190227
 INFO - Build time: 04:12
 INFO - ********************************************************************************
 INFO - openejb.home = /home/soro/git/apache/tomee/examples/async-methods
 INFO - openejb.base = /home/soro/git/apache/tomee/examples/async-methods
 INFO - Created new singletonService org.apache.openejb.cdi.ThreadSingletonServiceImpl@22f71333
 INFO - Succeeded in installing singleton service
 INFO - Using 'javax.ejb.embeddable.EJBContainer=true'
 INFO - Cannot find the configuration file [conf/openejb.xml].  Will attempt to create one for the beans deployed.
 INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service)
 INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager)
 INFO - Creating TransactionManager(id=Default Transaction Manager)
 INFO - Creating SecurityService(id=Default Security Service)
 INFO - Found EjbModule in classpath: /home/soro/git/apache/tomee/examples/async-methods/target/classes
 INFO - Beginning load: /home/soro/git/apache/tomee/examples/async-methods/target/classes
 INFO - Configuring enterprise application: /home/soro/git/apache/tomee/examples/async-methods
 INFO - Auto-deploying ejb JobProcessor: EjbDeployment(deployment-id=JobProcessor)
 INFO - Configuring Service(id=Default Singleton Container, type=Container, provider-id=Default Singleton Container)
 INFO - Auto-creating a container for bean JobProcessor: Container(type=SINGLETON, id=Default Singleton Container)
 INFO - Creating Container(id=Default Singleton Container)
 INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container)
 INFO - Auto-creating a container for bean org.superbiz.async.JobProcessorTest: Container(type=MANAGED, id=Default Managed Container)
 INFO - Creating Container(id=Default Managed Container)
 INFO - Using directory /tmp for stateful session passivation
 INFO - Enterprise application "/home/soro/git/apache/tomee/examples/async-methods" loaded.
 INFO - Assembling app: /home/soro/git/apache/tomee/examples/async-methods
 INFO - Jndi(name="java:global/async-methods/JobProcessor!org.superbiz.async.JobProcessor")
 INFO - Jndi(name="java:global/async-methods/JobProcessor")
 INFO - Existing thread singleton service in SystemInstance(): org.apache.openejb.cdi.ThreadSingletonServiceImpl@22f71333
 INFO - Some Principal APIs could not be loaded: org.eclipse.microprofile.jwt.JsonWebToken out of org.eclipse.microprofile.jwt.JsonWebToken not found
 INFO - OpenWebBeans Container is starting...
 INFO - Adding OpenWebBeansPlugin : [CdiPlugin]
 INFO - All injection points were validated successfully.
 INFO - OpenWebBeans Container has started, it took 316 ms.
 INFO - Created Ejb(deployment-id=JobProcessor, ejb-name=JobProcessor, container=Default Singleton Container)
 INFO - Started Ejb(deployment-id=JobProcessor, ejb-name=JobProcessor, container=Default Singleton Container)
 INFO - Deployed Application(path=/home/soro/git/apache/tomee/examples/async-methods)
 Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 23.491 sec

 Results :

 Tests run: 1, Failures: 0, Errors: 0, Skipped: 0</code></pre>
 </div>
 </div>
 </div>
 </div>
 <div class="sect1">
 <h2 id="_how_it_works_under_the_covers">How it works under the covers</h2>
 <div class="sectionbody">
 <div class="paragraph">
 <p>Under the covers what makes this work is:</p>
 </div>
 <div class="ulist">
 <ul>
 <li>
 <p>The <code>JobProcessor</code> the caller sees is not actually an instance of
 <code>JobProcessor</code>. Rather it’s a subclass or proxy that has all the methods
 overridden. Methods that are supposed to be asynchronous are handled
 differently.</p>
 </li>
 <li>
 <p>Calls to an asynchronous method simply result in a <code>Runnable</code> being
 created that wraps the method and parameters you gave. This runnable is
 given to an
 <a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Executor.html">Executor</a>
 which is simply a work queue attached to a thread pool.</p>
 </li>
 <li>
 <p>After adding the work to the queue, the proxied version of the method
 returns an implementation of <code>Future</code> that is linked to the <code>Runnable</code>
 which is now waiting on the queue.</p>
 </li>
 <li>
 <p>When the <code>Runnable</code> finally executes the method on the <em>real</em>
 <code>JobProcessor</code> instance, it will take the return value and set it into
 the <code>Future</code> making it available to the caller.</p>
 </li>
 </ul>
 </div>
 <div class="paragraph">
 <p>Important to note that the <code>AsyncResult</code> object the <code>JobProcessor</code>
 returns is not the same <code>Future</code> object the caller is holding. It would
 have been neat if the real <code>JobProcessor</code> could just return <code>String</code> and
 the caller’s version of <code>JobProcessor</code> could return <code>Future&lt;String&gt;</code>,
 but we didn’t see any way to do that without adding more complexity. So
 the <code>AsyncResult</code> is a simple wrapper object. The container will pull
 the <code>String</code> out, throw the <code>AsyncResult</code> away, then put the <code>String</code> in
 the <em>real</em> <code>Future</code> that the caller is holding.</p>
 </div>
 <div class="paragraph">
 <p>To get progress along the way, simply pass a thread-safe object like
 <a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/atomic/AtomicInteger.html">AtomicInteger</a>
 to the <code>@Asynchronous</code> method and have the bean code periodically update
 it with the percent complete.</p>
 </div>
 </div>
 </div>
 <div class="sect1">
 <h2 id="_related_examples">Related Examples</h2>
 <div class="sectionbody">
 <div class="paragraph">
 <p>For complex asynchronous processing, JavaEE’s answer is
 <code>@MessageDrivenBean</code>. Have a look at the
 <a href="../simple-mdb/README.html">simple-mdb</a> example</p>
 </div>
 </div>
 </div>
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	<div id="main-block" class="container main-block">
	<div class="row title">
	<div class="col-md-12">
	<div class='page-header'>

	<h1>@Asynchronous Methods</h1>
	</div>
	</div>
	</div>
	<div class="row">

	<div class="col-md-12">
	<div id="preamble">
	<div class="sectionbody">
	<div class="paragraph">
	<p>The @Asynchronous annotation was introduced in EJB 3.1 as a simple way
	of creating asynchronous processing.</p>
	</div>
	<div class="paragraph">
	<p>Every time a method annotated <code>@Asynchronous</code> is invoked by anyone it
	will immediately return regardless of how long the method actually
	takes. Each invocation returns a
	<a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Future.html">Future</a>
	object that essentially starts out <em>empty</em> and will later have its value
	filled in by the container when the related method call actually
	completes. Returning a <code>Future</code> object is not required and
	<code>@Asynchronous</code> methods can of course return <code>void</code>.</p>
	</div>
	</div>
	</div>
	<div class="sect1">
	<h2 id="_example">Example</h2>
	<div class="sectionbody">
	<div class="paragraph">
	<p>Here, in <code>JobProcessorTest</code>,</p>
	</div>
	<div class="paragraph">
	<p><code>final Future<String> red = processor.addJob("red");</code> proceeds to the
	next statement,</p>
	</div>
	<div class="paragraph">
	<p><code>final Future<String> orange = processor.addJob("orange");</code></p>
	</div>
	<div class="paragraph">
	<p>without waiting for the <code>addJob()</code> method to complete. And later we could
	ask for the result using the <code>Future<?>.get()</code> method like</p>
	</div>
	<div class="paragraph">
	<p><code>assertEquals("blue", blue.get());</code></p>
	</div>
	<div class="paragraph">
	<p>It waits for the processing to complete (if its not completed already)
	and gets the result. If you did not care about the result, you could
	simply have your asynchronous method as a <code>void</code> method.</p>
	</div>
	<div class="paragraph">
	<p><a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Future.html">Future</a>
	Object from docs,</p>
	</div>
	<div class="quoteblock">
	<blockquote>
	<div class="paragraph">
	<p>A Future represents the result of an asynchronous computation. Methods
	are provided to check if the computation is complete, to wait for its
	completion, and to retrieve the result of the computation. The result
	can only be retrieved using method get when the computation has
	completed, blocking if necessary until it is ready. Cancellation is
	performed by the cancel method. Additional methods are provided to
	determine if the task completed normally or was cancelled. Once a
	computation has completed, the computation cannot be cancelled. If you
	would like to use a Future for the sake of cancellability but not
	provide a usable result, you can declare types of the form Future<?> and
	return null as a result of the underlying task</p>
	</div>
	</blockquote>
	</div>
	</div>
	</div>
	<div class="sect1">
	<h2 id="_the_code">The code</h2>
	<div class="sectionbody">
	<div class="listingblock">
	<div class="content">
	<pre class="highlight"><code class="language-java" data-lang="java">@Singleton
	public class JobProcessor {
	@Asynchronous
	@Lock(READ)
	@AccessTimeout(-1)
	public Future<String> addJob(String jobName) {

	// Pretend this job takes a while
	doSomeHeavyLifting();

	// Return our result
	return new AsyncResult<String>(jobName);
	}

	private void doSomeHeavyLifting() {
	try {
	Thread.sleep(SECONDS.toMillis(10));
	} catch (InterruptedException e) {
	Thread.interrupted();
	throw new IllegalStateException(e);
	}
	}
	}</code></pre>
	</div>
	</div>
	</div>
	</div>
	<div class="sect1">
	<h2 id="_test">Test</h2>
	<div class="sectionbody">
	<div class="listingblock">
	<div class="content">
	<pre class="highlight"><code class="language-java" data-lang="java">public class JobProcessorTest extends TestCase {

	public void test() throws Exception {

	final Context context = EJBContainer.createEJBContainer().getContext();

	final JobProcessor processor = (JobProcessor) context.lookup("java:global/async-methods/JobProcessor");

	final long start = System.nanoTime();

	// Queue up a bunch of work
	final Future<String> red = processor.addJob("red");
	final Future<String> orange = processor.addJob("orange");
	final Future<String> yellow = processor.addJob("yellow");
	final Future<String> green = processor.addJob("green");
	final Future<String> blue = processor.addJob("blue");
	final Future<String> violet = processor.addJob("violet");

	// Wait for the result -- 1 minute worth of work
	assertEquals("blue", blue.get());
	assertEquals("orange", orange.get());
	assertEquals("green", green.get());
	assertEquals("red", red.get());
	assertEquals("yellow", yellow.get());
	assertEquals("violet", violet.get());

	// How long did it take?
	final long total = TimeUnit.NANOSECONDS.toSeconds(System.nanoTime() - start);

	// Execution should be around 9 - 21 seconds
	// The execution time depends on the number of threads available for asynchronous execution.
	// In the best case it is 10s plus some minimal processing time.
	assertTrue("Expected > 9 but was: " + total, total > 9);
	assertTrue("Expected < 21 but was: " + total, total < 21);

	}
	}</code></pre>
	</div>
	</div>
	<div class="listingblock">
	<div class="content">
	<pre class="highlight"><code class="language-console" data-lang="console">-------------------------------------------------------
	T E S T S
	-------------------------------------------------------
	Running org.superbiz.async.JobProcessorTest
	INFO - ********************************************************************************
	INFO - OpenEJB http://tomee.apache.org/
	INFO - Startup: Wed Feb 27 12:46:11 BRT 2019
	INFO - Copyright 1999-2018 (C) Apache OpenEJB Project, All Rights Reserved.
	INFO - Version: 8.0.0-SNAPSHOT
	INFO - Build date: 20190227
	INFO - Build time: 04:12
	INFO - ********************************************************************************
	INFO - openejb.home = /home/soro/git/apache/tomee/examples/async-methods
	INFO - openejb.base = /home/soro/git/apache/tomee/examples/async-methods
	INFO - Created new singletonService org.apache.openejb.cdi.ThreadSingletonServiceImpl@22f71333
	INFO - Succeeded in installing singleton service
	INFO - Using 'javax.ejb.embeddable.EJBContainer=true'
	INFO - Cannot find the configuration file [conf/openejb.xml]. Will attempt to create one for the beans deployed.
	INFO - Configuring Service(id=Default Security Service, type=SecurityService, provider-id=Default Security Service)
	INFO - Configuring Service(id=Default Transaction Manager, type=TransactionManager, provider-id=Default Transaction Manager)
	INFO - Creating TransactionManager(id=Default Transaction Manager)
	INFO - Creating SecurityService(id=Default Security Service)
	INFO - Found EjbModule in classpath: /home/soro/git/apache/tomee/examples/async-methods/target/classes
	INFO - Beginning load: /home/soro/git/apache/tomee/examples/async-methods/target/classes
	INFO - Configuring enterprise application: /home/soro/git/apache/tomee/examples/async-methods
	INFO - Auto-deploying ejb JobProcessor: EjbDeployment(deployment-id=JobProcessor)
	INFO - Configuring Service(id=Default Singleton Container, type=Container, provider-id=Default Singleton Container)
	INFO - Auto-creating a container for bean JobProcessor: Container(type=SINGLETON, id=Default Singleton Container)
	INFO - Creating Container(id=Default Singleton Container)
	INFO - Configuring Service(id=Default Managed Container, type=Container, provider-id=Default Managed Container)
	INFO - Auto-creating a container for bean org.superbiz.async.JobProcessorTest: Container(type=MANAGED, id=Default Managed Container)
	INFO - Creating Container(id=Default Managed Container)
	INFO - Using directory /tmp for stateful session passivation
	INFO - Enterprise application "/home/soro/git/apache/tomee/examples/async-methods" loaded.
	INFO - Assembling app: /home/soro/git/apache/tomee/examples/async-methods
	INFO - Jndi(name="java:global/async-methods/JobProcessor!org.superbiz.async.JobProcessor")
	INFO - Jndi(name="java:global/async-methods/JobProcessor")
	INFO - Existing thread singleton service in SystemInstance(): org.apache.openejb.cdi.ThreadSingletonServiceImpl@22f71333
	INFO - Some Principal APIs could not be loaded: org.eclipse.microprofile.jwt.JsonWebToken out of org.eclipse.microprofile.jwt.JsonWebToken not found
	INFO - OpenWebBeans Container is starting...
	INFO - Adding OpenWebBeansPlugin : [CdiPlugin]
	INFO - All injection points were validated successfully.
	INFO - OpenWebBeans Container has started, it took 316 ms.
	INFO - Created Ejb(deployment-id=JobProcessor, ejb-name=JobProcessor, container=Default Singleton Container)
	INFO - Started Ejb(deployment-id=JobProcessor, ejb-name=JobProcessor, container=Default Singleton Container)
	INFO - Deployed Application(path=/home/soro/git/apache/tomee/examples/async-methods)
	Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 23.491 sec

	Results :

	Tests run: 1, Failures: 0, Errors: 0, Skipped: 0</code></pre>
	</div>
	</div>
	</div>
	</div>
	<div class="sect1">
	<h2 id="_how_it_works_under_the_covers">How it works under the covers</h2>
	<div class="sectionbody">
	<div class="paragraph">
	<p>Under the covers what makes this work is:</p>
	</div>
	<div class="ulist">
	<ul>
	<li>
	<p>The <code>JobProcessor</code> the caller sees is not actually an instance of
	<code>JobProcessor</code>. Rather it’s a subclass or proxy that has all the methods
	overridden. Methods that are supposed to be asynchronous are handled
	differently.</p>
	</li>
	<li>
	<p>Calls to an asynchronous method simply result in a <code>Runnable</code> being
	created that wraps the method and parameters you gave. This runnable is
	given to an
	<a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Executor.html">Executor</a>
	which is simply a work queue attached to a thread pool.</p>
	</li>
	<li>
	<p>After adding the work to the queue, the proxied version of the method
	returns an implementation of <code>Future</code> that is linked to the <code>Runnable</code>
	which is now waiting on the queue.</p>
	</li>
	<li>
	<p>When the <code>Runnable</code> finally executes the method on the <em>real</em>
	<code>JobProcessor</code> instance, it will take the return value and set it into
	the <code>Future</code> making it available to the caller.</p>
	</li>
	</ul>
	</div>
	<div class="paragraph">
	<p>Important to note that the <code>AsyncResult</code> object the <code>JobProcessor</code>
	returns is not the same <code>Future</code> object the caller is holding. It would
	have been neat if the real <code>JobProcessor</code> could just return <code>String</code> and
	the caller’s version of <code>JobProcessor</code> could return <code>Future<String></code>,
	but we didn’t see any way to do that without adding more complexity. So
	the <code>AsyncResult</code> is a simple wrapper object. The container will pull
	the <code>String</code> out, throw the <code>AsyncResult</code> away, then put the <code>String</code> in
	the <em>real</em> <code>Future</code> that the caller is holding.</p>
	</div>
	<div class="paragraph">
	<p>To get progress along the way, simply pass a thread-safe object like
	<a href="http://download.oracle.com/javase/6/docs/api/java/util/concurrent/atomic/AtomicInteger.html">AtomicInteger</a>
	to the <code>@Asynchronous</code> method and have the bean code periodically update
	it with the percent complete.</p>
	</div>
	</div>
	</div>
	<div class="sect1">
	<h2 id="_related_examples">Related Examples</h2>
	<div class="sectionbody">
	<div class="paragraph">
	<p>For complex asynchronous processing, JavaEE’s answer is
	<code>@MessageDrivenBean</code>. Have a look at the
	<a href="../simple-mdb/README.html">simple-mdb</a> example</p>
	</div>
	</div>
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