162 lines
5.5 KiB
HTML
162 lines
5.5 KiB
HTML
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<head>
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<title>Akka Camel Samples with Scala</title>
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</head>
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<body>
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<div>
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<p>
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This tutorial contains 3 samples of
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<a href="http://doc.akka.io/docs/akka/2.3-SNAPSHOT/scala/camel.html" target="_blank">Akka Camel</a>.
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</p>
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<ul>
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<li>Asynchronous routing and transformation</li>
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<li>Custom Camel route</li>
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<li>Quartz scheduler</li>
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</ul>
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</div>
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<div>
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<h2>Asynchronous routing and transformation</h2>
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<p>
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This example demonstrates how to implement consumer and producer actors that
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support
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<a href="http://doc.akka.io/docs/akka/2.3-SNAPSHOT/scala/camel.html#Asynchronous_routing" target="_blank">
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Asynchronous routing</a> with their Camel endpoints. The sample
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application transforms the content of the Akka homepage, <a href="http://akka.io" target="_blank">http://akka.io</a>,
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by replacing every occurrence of *Akka* with *AKKA*.
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</p>
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<p>
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To run this example, go to the <a href="#run" class="shortcut">Run</a>
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tab, and start the application main class <code>sample.camel.HttpExample</code> if it's not already started.
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Then direct the browser to <a href="http://localhost:8875" target="_blank">http://localhost:8875</a> and the
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transformed Akka homepage should be displayed. Please note that this example will probably not work if you're
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behind an HTTP proxy.
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</p>
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<p>
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The following figure gives an overview how the example actors interact with
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external systems and with each other. A browser sends a GET request to
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http://localhost:8875 which is the published endpoint of the
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<a href="#code/src/main/scala/sample/camel/HttpExample.scala" class="shortcut">HttpConsumer</a>
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actor. The <code>HttpConsumer</code> actor forwards the requests to the
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<a href="#code/src/main/scala/sample/camel/HttpExample.scala" class="shortcut">HttpProducer</a>
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actor which retrieves the Akka homepage from http://akka.io. The retrieved HTML
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is then forwarded to the
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<a href="#code/src/main/scala/sample/camel/HttpExample.scala" class="shortcut">HttpTransformer</a>
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actor which replaces all occurrences of *Akka* with *AKKA*. The transformation result is sent back the HttpConsumer
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which finally returns it to the browser.
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</p>
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<img src="tutorial/camel-async-interact.png" width="400" />
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<p>
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Implementing the example actor classes and wiring them together is rather easy
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as shown in <a href="#code/src/main/scala/sample/camel/HttpExample.scala" class="shortcut">HttpExample.scala</a>.
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</p>
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<p>
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The <a href="http://camel.apache.org/jetty.html" target="_blank">jetty endpoints</a> of HttpConsumer and
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HttpProducer support asynchronous in-out message exchanges and do not allocate threads for the full duration of
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the exchange. This is achieved by using <a href="http://wiki.eclipse.org/Jetty/Feature/Continuations" target="_blank">Jetty continuations</a>
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on the consumer-side and by using <a href="http://wiki.eclipse.org/Jetty/Tutorial/HttpClient" target="_blank">Jetty's asynchronous HTTP client</a>
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on the producer side. The following high-level sequence diagram illustrates that.
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</p>
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<img src="tutorial/camel-async-sequence.png" width="400" />
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</div>
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<div>
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<h2>Custom Camel route example</h2>
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<p>
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This section also demonstrates the combined usage of a
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<a href="#code/src/main/scala/sample/camel/CustomRouteExample.scala" class="shortcut">RouteProducer</a>
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and a <a href="#code/src/main/scala/sample/camel/CustomRouteExample.scala" class="shortcut">RouteConsumer</a>
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actor as well as the inclusion of a
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<a href="#code/src/main/scala/sample/camel/CustomRouteExample.scala" class="shortcut">custom Camel route</a>.
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The following figure gives an overview.
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</p>
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<img src="tutorial/camel-custom-route.png" width="400" />
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<ul>
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<li>A consumer actor receives a message from an HTTP client</li>
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<li>It forwards the message to another actor that transforms the message (encloses
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the original message into hyphens)</li>
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<li>The transformer actor forwards the transformed message to a producer actor</li>
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<li>The producer actor sends the message to a custom Camel route beginning at the
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<code>direct:welcome</code> endpoint</li>
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<li>A processor (transformer) in the custom Camel route prepends "Welcome" to the
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original message and creates a result message</li>
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<li>The producer actor sends the result back to the consumer actor which returns
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it to the HTTP client</li>
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</ul>
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<p>
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The producer actor knows where to reply the message to because the consumer and
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transformer actors have forwarded the original sender reference as well. The
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application configuration and the route starting from direct:welcome are done in the code above.
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</p>
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<p>
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To run this example, go to the <a href="#run" class="shortcut">Run</a>
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tab, and start the application main class <code>sample.camel.CustomRouteExample</code>
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</p>
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<p>
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POST a message to <code>http://localhost:8877/camel/welcome</code>.
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</p>
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<pre><code>
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curl -H "Content-Type: text/plain" -d "Anke" http://localhost:8877/camel/welcome
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</code></pre>
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<p>
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The response should be:
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</p>
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<pre><code>
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Welcome - Anke -
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</code></pre>
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</div>
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<div>
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<h2>Quartz Scheduler Example</h2>
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<p>
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Here is an example showing how simple it is to implement a cron-style scheduler by
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using the Camel Quartz component in Akka.
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</p>
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<p>
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Open <a href="#code/src/main/scala/sample/camel/QuartzExample.scala" class="shortcut">QuartzExample.scala</a>.
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</p>
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<p>
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The example creates a "timer" actor which fires a message every 2
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seconds.
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</p>
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<p>
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For more information about the Camel Quartz component, see here:
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<a href="http://camel.apache.org/quartz.html" target="_blank">http://camel.apache.org/quartz.html</a>
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</p>
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</div>
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</body>
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</html>
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