svn commit: r1167463 - /openejb/trunk/openejb3/examples/async-methods/README.mdtext

[db...@apache.org]

Author: dblevins
Date: Sat Sep 10 05:47:42 2011
New Revision: 1167463

URL: http://svn.apache.org/viewvc?rev=1167463&view=rev
Log:
Patch from Vishwa, OPENEJB-1639: Documentation for examples/async-methods
I really like the detail in the descriptions.  Great links and wonderful closing thought on MDBs.  It's a perfect doc.

Added:
    openejb/trunk/openejb3/examples/async-methods/README.mdtext

Added: openejb/trunk/openejb3/examples/async-methods/README.mdtext
URL: http://svn.apache.org/viewvc/openejb/trunk/openejb3/examples/async-methods/README.mdtext?rev=1167463&view=auto
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--- openejb/trunk/openejb3/examples/async-methods/README.mdtext (added)
+++ openejb/trunk/openejb3/examples/async-methods/README.mdtext Sat Sep 10 05:47:42 2011
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+# @asynchronous Method
+
+The @asynchronous annotation was introduced in EJB 3.1 as a simple way of creating asynchronous processing.
+
+Asynchronous Processing is when a caller returns immediately without waiting for the invoked method to complete.
+
+Here, in `JobProcessorTest`,
+
+`  final Future<String> red = processor.addJob("red");`
+proceeds to the next statement,
+
+`  final Future<String> orange = processor.addJob("orange");`
+
+without waiting for the addJob() method to complete. And later we could ask for the result using the Future<?>.get() method like
+
+`assertEquals("blue", blue.get());`
+
+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 void method.
+
+
+[Future](http://download.oracle.com/javase/6/docs/api/java/util/concurrent/Future.html) Object from docs,
+
+> 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
+
+
+
+# The code
+<pre><code>
+    @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>
+# Test
+<pre><code>
+    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
+        assertTrue("" + total, total > 9);
+        assertTrue("" + total, total < 21);
+
+      }
+
+
+    }
+</code></pre>
+#Running
+<pre><code>
+-------------------------------------------------------
+ T E S T S
+-------------------------------------------------------
+Running org.superbiz.async.JobProcessorTest
+Apache OpenEJB 4.0.0-SNAPSHOT    build: 20110801-04:02
+http://openejb.apache.org/
+INFO - openejb.home = G:\Workspace\fullproject\openejb3\examples\async-methods
+INFO - openejb.base = G:\Workspace\fullproject\openejb3\examples\async-methods
+INFO - Using 'javax.ejb.embeddable.EJBContainer=true'
+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 - Found EjbModule in classpath: g:\Workspace\fullproject\openejb3\examples\async-methods\target\classes
+INFO - Beginning load: g:\Workspace\fullproject\openejb3\examples\async-methods\target\classes
+INFO - Configuring enterprise application: g:\Workspace\fullproject\openejb3\examples\async-methods
+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 - 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 - Enterprise application "g:\Workspace\fullproject\openejb3\examples\async-methods" loaded.
+INFO - Assembling app: g:\Workspace\fullproject\openejb3\examples\async-methods
+INFO - Jndi(name="java:global/async-methods/JobProcessor!org.superbiz.async.JobProcessor")
+INFO - Jndi(name="java:global/async-methods/JobProcessor")
+INFO - Jndi(name="java:global/EjbModule100568296/org.superbiz.async.JobProcessorTest!org.superbiz.async.JobProcessorTest")
+INFO - Jndi(name="java:global/EjbModule100568296/org.superbiz.async.JobProcessorTest")
+INFO - Created Ejb(deployment-id=org.superbiz.async.JobProcessorTest, ejb-name=org.superbiz.async.JobProcessorTest, container=Default Managed Container)
+INFO - Created Ejb(deployment-id=JobProcessor, ejb-name=JobProcessor, container=Default Singleton Container)
+INFO - Started Ejb(deployment-id=org.superbiz.async.JobProcessorTest, ejb-name=org.superbiz.async.JobProcessorTest, container=Default Managed Container)
+INFO - Started Ejb(deployment-id=JobProcessor, ejb-name=JobProcessor, container=Default Singleton Container)
+INFO - Deployed Application(path=g:\Workspace\fullproject\openejb3\examples\async-methods)
+Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 13.305 sec
+
+Results :
+
+Tests run: 1, Failures: 0, Errors: 0, Skipped: 0
+
+[INFO] ------------------------------------------------------------------------
+[INFO] BUILD SUCCESS
+[INFO] ------------------------------------------------------------------------
+[INFO] Total time: 21.097s
+[INFO] Finished at: Wed Aug 03 22:48:26 IST 2011
+[INFO] Final Memory: 13M/145M
+[INFO] ------------------------------------------------------------------------
+</code></pre>
+
+#Related Examples
+
+For complex asynchronous processing, JavaEE's answer is `MessageDrivenBean`. Have a look at the simple-mdb example