Modified: websites/production/camel/content/polling-consumer.html
==============================================================================
--- websites/production/camel/content/polling-consumer.html (original)
+++ websites/production/camel/content/polling-consumer.html Fri Aug 25 08:22:01
2017
@@ -36,17 +36,6 @@
<![endif]-->
- <link href='//camel.apache.org/styles/highlighter/styles/shCoreCamel.css'
rel='stylesheet' type='text/css' />
- <link href='//camel.apache.org/styles/highlighter/styles/shThemeCamel.css'
rel='stylesheet' type='text/css' />
- <script src='//camel.apache.org/styles/highlighter/scripts/shCore.js'
type='text/javascript'></script>
- <script src='//camel.apache.org/styles/highlighter/scripts/shBrushJava.js'
type='text/javascript'></script>
- <script src='//camel.apache.org/styles/highlighter/scripts/shBrushXml.js'
type='text/javascript'></script>
- <script src='//camel.apache.org/styles/highlighter/scripts/shBrushPlain.js'
type='text/javascript'></script>
-
- <script type="text/javascript">
- SyntaxHighlighter.defaults['toolbar'] = false;
- SyntaxHighlighter.all();
- </script>
<title>
Apache Camel: Polling Consumer
@@ -86,136 +75,18 @@
<tbody>
<tr>
<td valign="top" width="100%">
-<div class="wiki-content maincontent"><h3
id="PollingConsumer-PollingConsumer">Polling Consumer</h3><p>Camel supports
implementing the <a shape="rect" class="external-link"
href="http://www.enterpriseintegrationpatterns.com/PollingConsumer.html";
rel="nofollow">Polling Consumer</a> from the <a shape="rect"
href="enterprise-integration-patterns.html">EIP patterns</a> using the <a
shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html";>PollingConsumer</a>
interface which can be created via the <a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Endpoint.html#createPollingConsumer()">Endpoint.createPollingConsumer()</a>
method.</p><p><span class="confluence-embedded-file-wrapper"><img
class="confluence-embedded-image confluence-external-resource"
src="http://www.enterpriseintegrationpatterns.com/img/PollingConsumerSolution.gif";
data-image-src
="http://www.enterpriseintegrationpatterns.com/img/PollingConsumerSolution.gif";></span></p><p>In
Java:</p><div class="code panel pdl" style="border-width: 1px;"><div
class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[Endpoint endpoint =
context.getEndpoint("activemq:my.queue");
+<div class="wiki-content maincontent"><h3
id="PollingConsumer-PollingConsumer">Polling Consumer</h3><p>Camel supports
implementing the <a shape="rect" class="external-link"
href="http://www.enterpriseintegrationpatterns.com/PollingConsumer.html";
rel="nofollow">Polling Consumer</a> from the <a shape="rect"
href="enterprise-integration-patterns.html">EIP patterns</a> using the <a
shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html";>PollingConsumer</a>
interface which can be created via the <a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Endpoint.html#createPollingConsumer()">Endpoint.createPollingConsumer()</a>
method.</p><p><span class="confluence-embedded-file-wrapper"><img
class="confluence-embedded-image confluence-external-resource"
src="http://www.enterpriseintegrationpatterns.com/img/PollingConsumerSolution.gif";
data-image-src
="http://www.enterpriseintegrationpatterns.com/img/PollingConsumerSolution.gif";></span></p><p>In
Java:</p><parameter
ac:name="language">java</parameter><plain-text-body>Endpoint endpoint =
context.getEndpoint("activemq:my.queue");
PollingConsumer consumer = endpoint.createPollingConsumer();
Exchange exchange = consumer.receive();
-]]></script>
-</div></div><p>The <strong><code>ConsumerTemplate</code></strong> (discussed
below) is also available.</p><p>There are three main polling methods on <a
shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html";>PollingConsumer</a></p><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Method name</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><a shape="rect"
class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html#receive()">receive()</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Waits until a message is
available and then returns it; potentially blocking
forever</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><a
shape="rect" class="external-link
"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html#receive(long)">receive(long)</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Attempts to receive a message
exchange, waiting up to the given timeout and returning null if no message
exchange could be received within the time available</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><a shape="rect"
class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html#receiveNoWait()">receiveNoWait()</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Attempts to receive a message
exchange immediately without waiting and returning null if a message exchange
is not available yet</p></td></tr></tbody></table></div><h3
id="PollingConsumer-EventDrivenPollingConsumerOptions">EventDrivenPollingConsumer
Options</h3><p>The <strong><code>EventDrivePollingConsumer</code></strong>
(the def
ault implementation) supports the following options:</p><div
class="confluenceTableSmall"><div class="table-wrap"><table
class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1"
class="confluenceTh"><p>Option</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Default</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>pollingConsumerQueueSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>1000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel
2.14/2.13.1/2.12.4:</strong> The queue size for the internal hand-off queue
between the polling consumer, and producers sending data into the
queue.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>pollingConsumerBlockWhenFull</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td
colspan="1" rowspan="1" class="co
nfluenceTd"><p><strong>Camel 2.14/2.13.1/2.12/4:</strong> Whether to block any
producer if the internal queue is full.</p></td></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><span><code>pollingConsumerBlockTimeout</code></span></td><td
colspan="1" rowspan="1" class="confluenceTd">0</td><td colspan="1" rowspan="1"
class="confluenceTd"><strong>Camel 2.16:</strong> To use a timeout (in
milliseconds) when the producer is blocked if the internal queue is full. If
the value is <strong><code>0</code></strong> or negative then no timeout
is in use. If a timeout is triggered then
a <strong><code>ExchangeTimedOutException</code></strong> is
thrown.</td></tr></tbody></table></div></div>
-
-
-<p>Notice that some Camel <a shape="rect"
href="components.html">Components</a> has their own implementation
of <strong><code>PollingConsumer</code></strong> and therefore do not
support the options above.</p><p>You can configure these options in
endpoints <a shape="rect" href="uris.html">URIs</a>, such as shown
below:</p><div class="code panel pdl" style="border-width: 1px;"><div
class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[Endpoint endpoint =
context.getEndpoint("file:inbox?pollingConsumerQueueSize=50");
+</plain-text-body><p>The <strong><code>ConsumerTemplate</code></strong>
(discussed below) is also available.</p><p>There are three main polling methods
on <a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html";>PollingConsumer</a></p><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Method name</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>Description</p></th></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><a shape="rect"
class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html#receive()">receive()</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Waits until a message is
available and then returns it; potentially blocking
forever</p></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd"><p><a
shape="rect" class="externa
l-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html#receive(long)">receive(long)</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Attempts to receive a message
exchange, waiting up to the given timeout and returning null if no message
exchange could be received within the time available</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><a shape="rect"
class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html#receiveNoWait()">receiveNoWait()</a></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Attempts to receive a message
exchange immediately without waiting and returning null if a message exchange
is not available yet</p></td></tr></tbody></table></div><h3
id="PollingConsumer-EventDrivenPollingConsumerOptions">EventDrivenPollingConsumer
Options</h3><p>The <strong><code>EventDrivePollingConsumer</code></strong>
(t
he default implementation) supports the following options:</p><parameter
ac:name="class">confluenceTableSmall</parameter><rich-text-body><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Option</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Default</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>pollingConsumerQueueSize</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>1000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel
2.14/2.13.1/2.12.4:</strong> The queue size for the internal hand-off queue
between the polling consumer, and producers sending data into the
queue.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>pollingConsumerBlockWhenFull</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>true</code
></p></td><td colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel
>2.14/2.13.1/2.12/4:</strong> Whether to block any producer if the internal
>queue is full.</p></td></tr><tr><td colspan="1" rowspan="1"
>class="confluenceTd"><span><code>pollingConsumerBlockTimeout</code></span></td><td
> colspan="1" rowspan="1" class="confluenceTd">0</td><td colspan="1"
>rowspan="1" class="confluenceTd"><strong>Camel 2.16:</strong> To use a
>timeout (in milliseconds) when the producer is blocked if the internal queue
>is full. If the value is <strong><code>0</code></strong> or negative
>then no timeout is in use. If a timeout is triggered then
>a <strong><code>ExchangeTimedOutException</code></strong> is
>thrown.</td></tr></tbody></table></div></rich-text-body><p>Notice that some
>Camel <a shape="rect" href="components.html">Components</a> has
>their own implementation
>of <strong><code>PollingConsumer</code></strong> and therefore do not
>support the options above.</p><p>You can
configure these options in endpoints <a shape="rect"
href="uris.html">URIs</a>, such as shown below:</p><parameter
ac:name="language">java</parameter><plain-text-body>Endpoint endpoint =
context.getEndpoint("file:inbox?pollingConsumerQueueSize=50");
PollingConsumer consumer = endpoint.createPollingConsumer();
-Exchange exchange = consumer.receive(5000);]]></script>
-</div></div><h3
id="PollingConsumer-ConsumerTemplate">ConsumerTemplate</h3><p>The
<strong><code>ConsumerTemplate</code></strong> is a template much like
Spring's <strong><code>JmsTemplate</code></strong>
or <strong><code>JdbcTemplate</code></strong> supporting the <a
shape="rect" href="polling-consumer.html">Polling Consumer</a> EIP. With the
template you can consume <a shape="rect" href="exchange.html">Exchange</a>s
from an <a shape="rect" href="endpoint.html">Endpoint</a>. The template
supports the three operations listed above. However, it also includes
convenient methods for returning the body, etc
<strong><code>consumeBody</code></strong>.</p><p>Example:</p><div class="code
panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[Exchange exchange =
consumerTemplate.receive("activemq:my.queue");
-]]></script>
-</div></div><p>Or to extract and get the body you can do:</p><div class="code
panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[Object body =
consumerTemplate.receiveBody("activemq:my.queue");
-]]></script>
-</div></div><p>And you can provide the body type as a parameter and have it
returned as the type:</p><div class="code panel pdl" style="border-width:
1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[String body =
consumerTemplate.receiveBody("activemq:my.queue", String.class);
-]]></script>
-</div></div><p>You get hold of a
<strong><code>ConsumerTemplate</code></strong> from the
<strong><code>CamelContext</code></strong> with the
<strong><code>createConsumerTemplate</code></strong> operation:</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[ConsumerTemplate consumer =
context.createConsumerTemplate();
-]]></script>
-</div></div><h4 id="PollingConsumer-UsingConsumerTemplatewithSpringDSL">Using
ConsumerTemplate with Spring DSL</h4><p>With the Spring DSL we can declare the
consumer in the <strong><code>CamelContext</code></strong> with the
<strong><code>consumerTemplate</code></strong> tag, just like the
<strong><code>ProducerTemplate</code></strong>. The example below illustrates
this:</p><div class="code panel pdl" style="border-width: 1px;"><div
class="codeContent panelContent pdl">
-<script class="brush: xml; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-<camelContext xmlns="http://camel.apache.org/schema/spring">
- <!-- define a producer template -->
- <template id="producer"/>
- <!-- define a consumer template -->
- <consumerTemplate id="consumer"/>
- <!-- define endpoint -->
- <endpoint id="result" uri="mock:result"/>
-
- <route>
- <from uri="seda:foo"/>
- <to uri="ref:result"/>
- </route>
-</camelContext>
-]]></script>
-</div></div>Then we can get leverage Spring to inject the
<strong><code>ConsumerTemplate</code></strong> in our java class. The code
below is part of an unit test but it shows how the consumer and producer can
work together.<div class="code panel pdl" style="border-width: 1px;"><div
class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-@ContextConfiguration
-public class SpringConsumerTemplateTest extends SpringRunWithTestSupport {
-
- @Autowired
- private ProducerTemplate producer;
-
- @Autowired
- private ConsumerTemplate consumer;
-
- @EndpointInject(ref = "result")
- private MockEndpoint mock;
-
- @Test
- public void testConsumeTemplate() throws Exception {
- // we expect Hello World received in our mock endpoint
- mock.expectedBodiesReceived("Hello World");
-
- // we use the producer template to send a message to the seda:start
endpoint
- producer.sendBody("seda:start", "Hello World");
-
- // we consume the body from seda:start
- String body = consumer.receiveBody("seda:start",
String.class);
- assertEquals("Hello World", body);
-
- // and then we send the body again to seda:foo so it will be routed to
the mock
- // endpoint so our unit test can complete
- producer.sendBody("seda:foo", body);
-
- // assert mock received the body
- mock.assertIsSatisfied();
- }
-
-}
-]]></script>
-</div></div><h4 id="PollingConsumer-TimerBasedPollingConsumer">Timer Based
Polling Consumer</h4><p>In this sample we use a <a shape="rect"
href="timer.html">Timer</a> to schedule a route to be started every 5th second
and invoke our bean <strong><code>MyCoolBean</code></strong> where we
implement the business logic for the <a shape="rect"
href="polling-consumer.html">Polling Consumer</a>. Here we want to consume all
messages from a JMS queue, process the message and send them to the next
queue.</p><p>First we setup our route as:</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-MyCoolBean cool = new MyCoolBean();
-cool.setProducer(template);
-cool.setConsumer(consumer);
-
-from("timer://foo?period=5000").bean(cool,
"someBusinessLogic");
-
-from("activemq:queue.foo").to("mock:result");
-]]></script>
-</div></div>And then we have out logic in our bean:<div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-public static class MyCoolBean {
-
- private int count;
- private ConsumerTemplate consumer;
- private ProducerTemplate producer;
-
- public void setConsumer(ConsumerTemplate consumer) {
- this.consumer = consumer;
- }
-
- public void setProducer(ProducerTemplate producer) {
- this.producer = producer;
- }
-
- public void someBusinessLogic() {
- // loop to empty queue
- while (true) {
- // receive the message from the queue, wait at most 3 sec
- String msg =
consumer.receiveBody("activemq:queue.inbox", 3000, String.class);
- if (msg == null) {
- // no more messages in queue
- break;
- }
-
- // do something with body
- msg = "Hello " + msg;
-
- // send it to the next queue
- producer.sendBodyAndHeader("activemq:queue.foo", msg,
"number", count++);
- }
- }
-}
-]]></script>
-</div></div><h3 id="PollingConsumer-ScheduledPollComponents">Scheduled Poll
Components</h3><p>Quite a few inbound Camel endpoints use a scheduled poll
pattern to receive messages and push them through the Camel processing routes.
That is to say externally from the client the endpoint appears to use an <a
shape="rect" href="event-driven-consumer.html">Event Driven Consumer</a> but
internally a scheduled poll is used to monitor some kind of state or resource
and then fire message exchanges.</p><p>Since this a such a common pattern,
polling components can extend the <a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/impl/ScheduledPollConsumer.html";>ScheduledPollConsumer</a>
base class which makes it simpler to implement this pattern. There is also the
<a shape="rect" href="quartz.html">Quartz Component</a> which provides
scheduled delivery of messages using the Quartz enterprise scheduler.</p><p>For
more details see:</p
><ul><li><a shape="rect" class="external-link"
>href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/PollingConsumer.html";>PollingConsumer</a></li><li>Scheduled
> Polling Components<ul><li><a shape="rect" class="external-link"
>href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/impl/ScheduledPollConsumer.html";>ScheduledPollConsumer</a></li><li><a
> shape="rect" href="scheduler.html">Scheduler</a></li><li><a shape="rect"
>href="atom.html">Atom</a></li><li><a shape="rect"
>href="beanstalk.html">Beanstalk</a></li><li><a shape="rect"
>href="file2.html">File</a></li><li><a shape="rect"
>href="ftp2.html">FTP</a></li><li><a shape="rect"
>href="hbase.html">hbase</a></li><li><a shape="rect"
>href="ibatis.html">iBATIS</a></li><li><a shape="rect"
>href="jpa.html">JPA</a></li><li><a shape="rect"
>href="mail.html">Mail</a></li><li><a shape="rect"
>href="mybatis.html">MyBatis</a></li><li><a shape="rect"
>href="quartz.html">Quartz</a></li><li><a shape="rect"
href="snmp.html">SNMP</a></li><li><a shape="rect"
href="aws-s3.html">AWS-S3</a></li><li><a shape="rect"
href="aws-sqs.html">AWS-SQS</a></li></ul></li></ul><h3
id="PollingConsumer-ScheduledPollConsumerOptions">ScheduledPollConsumer
Options</h3><p>The <strong><code>ScheduledPollConsumer</code></strong>
supports the following options:</p><div class="confluenceTableSmall"><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Option</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Default</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>backoffErrorThreshold</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong>
The number of subsequent error polls (failed due some error) that should happen
before
the <strong><code>backoffMultipler</code></strong> should
kick-in.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>backoffIdleThreshold</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong>
The number of subsequent idle polls that should happen before the
<strong><code>backoffMultipler</code></strong> should
kick-in.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>backoffMultiplier</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong> To let the
scheduled polling consumer back-off if there has been a number of subsequent
idles/errors in a row. The multiplier is then the number of polls that will be
skipped before the next actual attempt is happening again. When this option is
in use then <strong><cod
e>backoffIdleThreshold</code></strong> and/or
<strong><code>backoffErrorThreshold</code></strong> must also be
configured.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>delay</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>500</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>Milliseconds before the next poll.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>greedy</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel
2.10.6/2.11.1:</strong> If greedy is enabled, then
the <strong><code>ScheduledPollConsumer</code></strong> will run
immediately again, if the previous run polled 1 or more
messages.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>initialDelay</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>1000</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Milliseconds before the first
poll starts.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>pollStrategy</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"> </td><td colspan="1" rowspan="1"
class="confluenceTd"><p>A pluggable
<strong><code>org.apache.camel.PollingConsumerPollingStrategy</code></strong>
allowing you to provide your custom implementation to control error handling
usually occurred during the <strong><code>poll</code></strong> operation
<em><strong>before</strong></em> an <a shape="rect"
href="exchange.html">Exchange</a> has been created and routed in Camel. In
other words the error occurred while the polling was gathering information, for
instance access to a file network failed so Camel cannot access it to scan for
files.</p><p>The default implementation will log the caused exception at
<strong><code>WARN</code></strong> level and ignore it.</p></td></tr><tr><td
colspan="1" row
span="1" class="confluenceTd"><p><code>runLoggingLevel</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>TRACE</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.8:</strong> The
consumer logs a start/complete log line when it polls. This option allows you
to configure the logging level for that.</p></td></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>scheduledExecutorService</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.10:</strong>
Allows for configuring a custom/shared thread pool to use for the consumer. By
default each consumer has its own single threaded thread pool. This option
allows you to share a thread pool among multiple
consumers.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>scheduler</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code
>null</code></p></td><td colspan="1" rowspan="1"
>class="confluenceTd"><p><strong>Camel 2.12:</strong> Allow to plugin a custom
><strong><code>org.apache.camel.spi.ScheduledPollConsumerScheduler</code></strong>
> to use as the scheduler for firing when the polling consumer runs. The
>default implementation uses the
><strong><code>ScheduledExecutorService</code></strong> and there is a <a
>shape="rect" href="quartz2.html">Quartz2</a>, and <a shape="rect"
>href="spring.html">Spring</a> based which supports CRON expressions.
><strong>Notice:</strong> If using a custom scheduler then the options for
><strong><code>initialDelay</code>, <code>useFixedDelay</code></strong>,
><strong><code>timeUnit</code></strong> and
><strong><code>scheduledExecutorService</code></strong> may not be in use. Use
>the text <strong><code>quartz2</code></strong> to refer to use the <a
>shape="rect" href="quartz2.html">Quartz2</a> scheduler; and use the text
><code>spring</code> to use the <a shape="rect" href="spring.html">S
pring</a> based; and use the text <strong><code>#myScheduler</code></strong>
to refer to a custom scheduler by its id in the <a shape="rect"
href="registry.html">Registry</a>.</p><p>See <a shape="rect"
href="quartz2.html">Quartz2</a> page for an example.</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>scheduler.xxx</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong> To configure
additional properties when using a custom
<strong><code>scheduler</code></strong> or any of the <a shape="rect"
href="quartz2.html">Quartz2</a>, <a shape="rect" href="spring.html">Spring</a>
based scheduler.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>sendEmptyMessageWhenIdle</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Came
l 2.9:</strong> If the polling consumer did not poll any files, you can enable
this option to send an empty message (no body) instead.</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>startScheduler</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Whether the scheduler should be auto
started.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>timeUnit</code></p></td><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>TimeUnit.MILLISECONDS</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Time unit for
<strong><code>initialDelay</code></strong> and
<strong><code>delay</code></strong> options.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>useFixedDelay</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Contro
ls if fixed delay or fixed rate is used. See <a shape="rect"
class="external-link"
href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/ScheduledExecutorService.html";
rel="nofollow">ScheduledExecutorService</a> in JDK for details. In
<strong>Camel 2.7.x</strong> or older the default value is
<strong><code>false</code></strong>.</p><p>From <strong>Camel 2.8</strong>: the
default value is
<strong><code>true</code></strong>.</p></td></tr></tbody></table></div></div>
-
-
-<h3
id="PollingConsumer-UsingbackofftoLettheSchedulerbeLessAggressive">Using <code>backoff</code>
to Let the Scheduler be Less Aggressive</h3><p><strong>Available as of Camel
2.12</strong></p><p>The scheduled <a shape="rect"
href="polling-consumer.html">Polling Consumer</a> is by default static by using
the same poll frequency whether or not there is messages to pickup or
not.</p><p>From <strong>Camel 2.12</strong>: you can configure the scheduled <a
shape="rect" href="polling-consumer.html">Polling Consumer</a> to be more
dynamic by using <strong><code>backoff</code></strong>. This allows the
scheduler to skip N number of polls when it becomes idle, or there has been X
number of errors in a row. See more details in the table above for the
<strong><code>backoffXXX</code></strong> options.</p><p>For example to let a
FTP consumer back-off if its becoming idle for a while you can do:</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl
">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[from("ftp://myserver?username=foo&passowrd=secret?delete=true&delay=5s&backoffMultiplier=6&backoffIdleThreshold=5")
- .to("bean:processFile");
-]]></script>
-</div></div><p>In this example, the FTP consumer will poll for new FTP files
every 5th second. But if it has been idle for 5 attempts in a row, then it will
back-off using a multiplier of 6, which means it will now poll every 5 x 6 =
30th second instead. When the consumer eventually pickup a file, then the
back-off will reset, and the consumer will go back and poll every 5th second
again.</p><p>Camel will log at <strong><code>DEBUG</code></strong> level using
<strong><code>org.apache.camel.impl.ScheduledPollConsumer</code></strong> when
back-off is kicking-in.</p><h3
id="PollingConsumer-AboutErrorHandlingandScheduledPollingConsumers">About Error
Handling and Scheduled Polling Consumers</h3><p><a shape="rect"
class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/impl/ScheduledPollConsumer.html";>ScheduledPollConsumer</a>
is scheduled based and its <strong><code>run</code></strong> method is invoked
periodically based on schedule settings
. But errors can also occur when a poll is being executed. For instance if
Camel should poll a file network, and this network resource is not available
then a <strong><code>java.io.IOException</code></strong> could occur. As this
error happens <strong>before</strong> any <a shape="rect"
href="exchange.html">Exchange</a> has been created and prepared for routing,
then the regular <a shape="rect" href="error-handling-in-camel.html">Error
handling in Camel</a> does not apply. So what does the consumer do then? Well
the exception is propagated back to the <strong><code>run</code></strong>
method where its handled. Camel will by default log the exception at
<strong><code>WARN</code></strong> level and then ignore it. At next schedule
the error could have been resolved and thus being able to poll the endpoint
successfully.</p><h3 id="PollingConsumer-UsingaCustomScheduler">Using a Custom
Scheduler</h3><p><strong>Available as of Camel 2.12:</strong></p><p>The SPI
interface <strong><code>org
.apache.camel.spi.ScheduledPollConsumerScheduler</code></strong> allows to
implement a custom scheduler to control when the <a shape="rect"
href="polling-consumer.html">Polling Consumer</a> runs. The default
implementation is based on the JDKs
<strong><code>ScheduledExecutorService</code></strong> with a single thread in
the thread pool. There is a CRON based implementation in the <a shape="rect"
href="quartz2.html">Quartz2</a>, and <a shape="rect"
href="spring.html">Spring</a> components.</p><p>For an example of developing
and using a custom scheduler, see the unit test
<strong><code>org.apache.camel.component.file.FileConsumerCustomSchedulerTest</code></strong>
from the source code in <strong><code>camel-core</code></strong>.</p><h4
id="PollingConsumer-ErrorHandlingWhenUsingPollingConsumerPollStrategy">Error
Handling When
Using <code>PollingConsumerPollStrategy</code></h4><p><strong><code>org.apache.camel.PollingConsumerPollStrategy</code></strong>
is a pluggable strategy tha
t you can configure on the
<strong><code>ScheduledPollConsumer</code></strong>. The default implementation
<strong><code>org.apache.camel.impl.DefaultPollingConsumerPollStrategy</code></strong>
will log the caused exception at <strong><code>WARN</code></strong> level and
then ignore this issue.</p><p>The strategy interface provides the following
three methods:</p><ul
class="alternate"><li><strong><code>begin</code></strong><br clear="none"><ul
class="alternate"><li><code>void begin(Consumer consumer, Endpoint
endpoint)</code></li></ul></li><li><strong><code>begin</code></strong> (<strong>Camel
2.3</strong>)<ul class="alternate"><li><code>boolean begin(Consumer consumer,
Endpoint
endpoint)</code></li></ul></li><li><strong><code>commit</code></strong><br
clear="none"><ul class="alternate"><li><code>void commit(Consumer consumer,
Endpoint
endpoint)</code></li></ul></li><li><strong><code>commit</code></strong> (<strong>Camel
2.6</strong>)<ul class="alternate"><li><code>void co
mmit(Consumer consumer, Endpoint endpoint, int
polledMessages)</code></li></ul></li><li><strong><code>rollback</code></strong><br
clear="none"><ul class="alternate"><li><code>boolean rollback(Consumer
consumer, Endpoint endpoint, int retryCounter, Exception e) throws
Exception</code></li></ul></li></ul><p>In <strong>Camel 2.3</strong>: the begin
method returns a <strong><code>boolean</code></strong> which indicates
whether or not to skipping polling. So you can implement your custom logic and
return <strong><code>false</code></strong> if you do not want to poll this
time.</p><p>In <strong>Camel 2.6</strong>: the commit method has an additional
parameter containing the number of message that was actually polled. For
example if there was no messages polled, the value would be zero, and you can
react accordingly.</p><p>The most interesting is the
<strong><code>rollback</code></strong> as it allows you do handle the caused
exception and decide what to do.</p><p>For instance if we w
ant to provide a retry feature to a scheduled consumer we can implement the
<strong><code>PollingConsumerPollStrategy</code></strong> method and put the
retry logic in the <strong><code>rollback</code></strong> method. Lets just
retry up till three times:</p><div class="code panel pdl" style="border-width:
1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[public boolean rollback(Consumer consumer,
Endpoint endpoint, int retryCounter, Exception e) throws Exception {
+Exchange exchange = consumer.receive(5000);</plain-text-body><h3
id="PollingConsumer-ConsumerTemplate">ConsumerTemplate</h3><p>The
<strong><code>ConsumerTemplate</code></strong> is a template much like
Spring's <strong><code>JmsTemplate</code></strong>
or <strong><code>JdbcTemplate</code></strong> supporting the <a
shape="rect" href="polling-consumer.html">Polling Consumer</a> EIP. With the
template you can consume <a shape="rect" href="exchange.html">Exchange</a>s
from an <a shape="rect" href="endpoint.html">Endpoint</a>. The template
supports the three operations listed above. However, it also includes
convenient methods for returning the body, etc
<strong><code>consumeBody</code></strong>.</p><p>Example:</p><plain-text-body>Exchange
exchange = consumerTemplate.receive("activemq:my.queue");
+</plain-text-body><p>Or to extract and get the body you can
do:</p><plain-text-body>Object body =
consumerTemplate.receiveBody("activemq:my.queue");
+</plain-text-body><p>And you can provide the body type as a parameter and have
it returned as the type:</p><plain-text-body>String body =
consumerTemplate.receiveBody("activemq:my.queue", String.class);
+</plain-text-body><p>You get hold of a
<strong><code>ConsumerTemplate</code></strong> from the
<strong><code>CamelContext</code></strong> with the
<strong><code>createConsumerTemplate</code></strong>
operation:</p><plain-text-body>ConsumerTemplate consumer =
context.createConsumerTemplate();
+</plain-text-body><h4
id="PollingConsumer-UsingConsumerTemplatewithSpringDSL">Using ConsumerTemplate
with Spring DSL</h4><p>With the Spring DSL we can declare the consumer in
the <strong><code>CamelContext</code></strong> with the
<strong><code>consumerTemplate</code></strong> tag, just like the
<strong><code>ProducerTemplate</code></strong>. The example below illustrates
this:<plain-text-body>{snippet:id=e1|lang=xml|url=camel/components/camel-spring/src/test/resources/org/apache/camel/spring/SpringConsumerTemplateTest-context.xml}</plain-text-body>Then
we can get leverage Spring to inject the
<strong><code>ConsumerTemplate</code></strong> in our java class. The code
below is part of an unit test but it shows how the consumer and producer can
work
together.<plain-text-body>{snippet:id=e1|lang=java|url=camel/components/camel-spring/src/test/java/org/apache/camel/spring/SpringConsumerTemplateTest.java}</plain-text-body></p><h4
id="PollingConsumer-TimerBasedPollingConsumer">Timer
Based Polling Consumer</h4><p>In this sample we use a <a shape="rect"
href="timer.html">Timer</a> to schedule a route to be started every 5th second
and invoke our bean <strong><code>MyCoolBean</code></strong> where we
implement the business logic for the <a shape="rect"
href="polling-consumer.html">Polling Consumer</a>. Here we want to consume all
messages from a JMS queue, process the message and send them to the next
queue.</p><p>First we setup our route
as:<plain-text-body>{snippet:id=e1|lang=java|url=camel/tags/camel-2.6.0/components/camel-jms/src/test/java/org/apache/camel/component/jms/JmsTimerBasedPollingConsumerTest.java}</plain-text-body>And
then we have out logic in our
bean:<plain-text-body>{snippet:id=e2|lang=java|url=camel/tags/camel-2.6.0/components/camel-jms/src/test/java/org/apache/camel/component/jms/JmsTimerBasedPollingConsumerTest.java}</plain-text-body></p><h3
id="PollingConsumer-ScheduledPollComponents">Scheduled Poll
Components</h3><p>Quite a few inbound
Camel endpoints use a scheduled poll pattern to receive messages and push them
through the Camel processing routes. That is to say externally from the client
the endpoint appears to use an <a shape="rect"
href="event-driven-consumer.html">Event Driven Consumer</a> but internally a
scheduled poll is used to monitor some kind of state or resource and then fire
message exchanges.</p><p>Since this a such a common pattern, polling components
can extend the <a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/impl/ScheduledPollConsumer.html";>ScheduledPollConsumer</a>
base class which makes it simpler to implement this pattern. There is also the
<a shape="rect" href="quartz.html">Quartz Component</a> which provides
scheduled delivery of messages using the Quartz enterprise scheduler.</p><p>For
more details see:</p><ul><li><a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/
apache/camel/PollingConsumer.html">PollingConsumer</a></li><li>Scheduled
Polling Components<ul><li><a shape="rect" class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/impl/ScheduledPollConsumer.html";>ScheduledPollConsumer</a></li><li><a
shape="rect" href="scheduler.html">Scheduler</a></li><li><a shape="rect"
href="atom.html">Atom</a></li><li><a shape="rect"
href="beanstalk.html">Beanstalk</a></li><li><a shape="rect"
href="file2.html">File</a></li><li><a shape="rect"
href="ftp2.html">FTP</a></li><li><a shape="rect"
href="hbase.html">hbase</a></li><li><a shape="rect"
href="ibatis.html">iBATIS</a></li><li><a shape="rect"
href="jpa.html">JPA</a></li><li><a shape="rect"
href="mail.html">Mail</a></li><li><a shape="rect"
href="mybatis.html">MyBatis</a></li><li><a shape="rect"
href="quartz.html">Quartz</a></li><li><a shape="rect"
href="snmp.html">SNMP</a></li><li><a shape="rect"
href="aws-s3.html">AWS-S3</a></li><li><a shape="rect" href="aws
-sqs.html">AWS-SQS</a></li></ul></li></ul><h3
id="PollingConsumer-ScheduledPollConsumerOptions">ScheduledPollConsumer
Options</h3><p>The <strong><code>ScheduledPollConsumer</code></strong>
supports the following options:</p><parameter
ac:name="class">confluenceTableSmall</parameter><rich-text-body><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Option</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Default</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Description</p></th></tr><tr><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>backoffErrorThreshold</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong>
The number of subsequent error polls (failed due some error) that should happen
before the <strong><code>backoffMultipler</code></strong> should kick-in.</p></t
d></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>backoffIdleThreshold</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong>
The number of subsequent idle polls that should happen before the
<strong><code>backoffMultipler</code></strong> should
kick-in.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>backoffMultiplier</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>0</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong> To let the
scheduled polling consumer back-off if there has been a number of subsequent
idles/errors in a row. The multiplier is then the number of polls that will be
skipped before the next actual attempt is happening again. When this option is
in use then <strong><code>backoffIdleThreshold</code></strong> and/or
<strong><code>backoffErrorT
hreshold</code></strong> must also be configured.</p></td></tr><tr><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>delay</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>500</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Milliseconds before the next
poll.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>greedy</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>false</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><strong>Camel 2.10.6/2.11.1:</strong> If greedy is
enabled, then the <strong><code>ScheduledPollConsumer</code></strong> will
run immediately again, if the previous run polled 1 or more
messages.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>initialDelay</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>1000</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Milliseconds before the f
irst poll starts.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>pollStrategy</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"> </td><td colspan="1" rowspan="1"
class="confluenceTd"><p>A pluggable
<strong><code>org.apache.camel.PollingConsumerPollingStrategy</code></strong>
allowing you to provide your custom implementation to control error handling
usually occurred during the <strong><code>poll</code></strong> operation
<em><strong>before</strong></em> an <a shape="rect"
href="exchange.html">Exchange</a> has been created and routed in Camel. In
other words the error occurred while the polling was gathering information, for
instance access to a file network failed so Camel cannot access it to scan for
files.</p><p>The default implementation will log the caused exception at
<strong><code>WARN</code></strong> level and ignore it.</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>runLoggingLevel</code></p></td><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>TRACE</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><strong>Camel 2.8:</strong> The consumer logs a
start/complete log line when it polls. This option allows you to configure the
logging level for that.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>scheduledExecutorService</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.10:</strong>
Allows for configuring a custom/shared thread pool to use for the consumer. By
default each consumer has its own single threaded thread pool. This option
allows you to share a thread pool among multiple
consumers.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>scheduler</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>
<strong>Camel 2.12:</strong> Allow to plugin a custom
<strong><code>org.apache.camel.spi.ScheduledPollConsumerScheduler</code></strong>
to use as the scheduler for firing when the polling consumer runs. The default
implementation uses the <strong><code>ScheduledExecutorService</code></strong>
and there is a <a shape="rect" href="quartz2.html">Quartz2</a>, and <a
shape="rect" href="spring.html">Spring</a> based which supports CRON
expressions. <strong>Notice:</strong> If using a custom scheduler then the
options for <strong><code>initialDelay</code>,
<code>useFixedDelay</code></strong>, <strong><code>timeUnit</code></strong> and
<strong><code>scheduledExecutorService</code></strong> may not be in use. Use
the text <strong><code>quartz2</code></strong> to refer to use the <a
shape="rect" href="quartz2.html">Quartz2</a> scheduler; and use the text
<code>spring</code> to use the <a shape="rect" href="spring.html">Spring</a>
based; and use the text <strong><code>#myScheduler</code></stro
ng> to refer to a custom scheduler by its id in the <a shape="rect"
href="registry.html">Registry</a>.</p><p>See <a shape="rect"
href="quartz2.html">Quartz2</a> page for an example.</p></td></tr><tr><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>scheduler.xxx</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>null</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><strong>Camel 2.12:</strong> To configure
additional properties when using a custom
<strong><code>scheduler</code></strong> or any of the <a shape="rect"
href="quartz2.html">Quartz2</a>, <a shape="rect" href="spring.html">Spring</a>
based scheduler.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>sendEmptyMessageWhenIdle</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><code>false</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.9:</strong> If
the polling consumer did not poll any files, you can e
nable this option to send an empty message (no body)
instead.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>startScheduler</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>true</code></p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Whether the scheduler should be auto
started.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>timeUnit</code></p></td><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>TimeUnit.MILLISECONDS</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>Time unit for
<strong><code>initialDelay</code></strong> and
<strong><code>delay</code></strong> options.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>useFixedDelay</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p> </p></td><td colspan="1"
rowspan="1" class="confluenceTd"><p>Controls if fixed delay or fixed rate is
used. See <a shape="rect" class="exter
nal-link"
href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/concurrent/ScheduledExecutorService.html";
rel="nofollow">ScheduledExecutorService</a> in JDK for details. In
<strong>Camel 2.7.x</strong> or older the default value is
<strong><code>false</code></strong>.</p><p>From <strong>Camel 2.8</strong>: the
default value is
<strong><code>true</code></strong>.</p></td></tr></tbody></table></div></rich-text-body><h3
id="PollingConsumer-UsingbackofftoLettheSchedulerbeLessAggressive">Using <code>backoff</code>
to Let the Scheduler be Less Aggressive</h3><p><strong>Available as of Camel
2.12</strong></p><p>The scheduled <a shape="rect"
href="polling-consumer.html">Polling Consumer</a> is by default static by using
the same poll frequency whether or not there is messages to pickup or
not.</p><p>From <strong>Camel 2.12</strong>: you can configure the scheduled <a
shape="rect" href="polling-consumer.html">Polling Consumer</a> to be more
dynamic by using <strong><code>backoff</code
></strong>. This allows the scheduler to skip N number of polls when it
>becomes idle, or there has been X number of errors in a row. See more details
>in the table above for the <strong><code>backoffXXX</code></strong>
>options.</p><p>For example to let a FTP consumer back-off if its becoming
>idle for a while you can do:</p><parameter
>ac:name="language">java</parameter><plain-text-body>from("ftp://myserver?username=foo&passowrd=secret?delete=true&delay=5s&backoffMultiplier=6&backoffIdleThreshold=5";)
+ .to("bean:processFile");
+</plain-text-body><p>In this example, the FTP consumer will poll for new FTP
files every 5th second. But if it has been idle for 5 attempts in a row, then
it will back-off using a multiplier of 6, which means it will now poll every 5
x 6 = 30th second instead. When the consumer eventually pickup a file, then the
back-off will reset, and the consumer will go back and poll every 5th second
again.</p><p>Camel will log at <strong><code>DEBUG</code></strong> level using
<strong><code>org.apache.camel.impl.ScheduledPollConsumer</code></strong> when
back-off is kicking-in.</p><h3
id="PollingConsumer-AboutErrorHandlingandScheduledPollingConsumers">About Error
Handling and Scheduled Polling Consumers</h3><p><a shape="rect"
class="external-link"
href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/impl/ScheduledPollConsumer.html";>ScheduledPollConsumer</a>
is scheduled based and its <strong><code>run</code></strong> method is invoked
periodically based on schedule se
ttings. But errors can also occur when a poll is being executed. For instance
if Camel should poll a file network, and this network resource is not available
then a <strong><code>java.io.IOException</code></strong> could occur. As this
error happens <strong>before</strong> any <a shape="rect"
href="exchange.html">Exchange</a> has been created and prepared for routing,
then the regular <a shape="rect" href="error-handling-in-camel.html">Error
handling in Camel</a> does not apply. So what does the consumer do then? Well
the exception is propagated back to the <strong><code>run</code></strong>
method where its handled. Camel will by default log the exception at
<strong><code>WARN</code></strong> level and then ignore it. At next schedule
the error could have been resolved and thus being able to poll the endpoint
successfully.</p><h3 id="PollingConsumer-UsingaCustomScheduler">Using a Custom
Scheduler</h3><p><strong>Available as of Camel 2.12:</strong></p><p>The SPI
interface <strong><co
de>org.apache.camel.spi.ScheduledPollConsumerScheduler</code></strong> allows
to implement a custom scheduler to control when the <a shape="rect"
href="polling-consumer.html">Polling Consumer</a> runs. The default
implementation is based on the JDKs
<strong><code>ScheduledExecutorService</code></strong> with a single thread in
the thread pool. There is a CRON based implementation in the <a shape="rect"
href="quartz2.html">Quartz2</a>, and <a shape="rect"
href="spring.html">Spring</a> components.</p><p>For an example of developing
and using a custom scheduler, see the unit test
<strong><code>org.apache.camel.component.file.FileConsumerCustomSchedulerTest</code></strong>
from the source code in <strong><code>camel-core</code></strong>.</p><h4
id="PollingConsumer-ErrorHandlingWhenUsingPollingConsumerPollStrategy">Error
Handling When
Using <code>PollingConsumerPollStrategy</code></h4><p><strong><code>org.apache.camel.PollingConsumerPollStrategy</code></strong>
is a pluggable strate
gy that you can configure on the
<strong><code>ScheduledPollConsumer</code></strong>. The default implementation
<strong><code>org.apache.camel.impl.DefaultPollingConsumerPollStrategy</code></strong>
will log the caused exception at <strong><code>WARN</code></strong> level and
then ignore this issue.</p><p>The strategy interface provides the following
three methods:</p><ul
class="alternate"><li><strong><code>begin</code></strong><br clear="none"><ul
class="alternate"><li><code>void begin(Consumer consumer, Endpoint
endpoint)</code></li></ul></li><li><strong><code>begin</code></strong> (<strong>Camel
2.3</strong>)<ul class="alternate"><li><code>boolean begin(Consumer consumer,
Endpoint
endpoint)</code></li></ul></li><li><strong><code>commit</code></strong><br
clear="none"><ul class="alternate"><li><code>void commit(Consumer consumer,
Endpoint
endpoint)</code></li></ul></li><li><strong><code>commit</code></strong> (<strong>Camel
2.6</strong>)<ul class="alternate"><li><code>v
oid commit(Consumer consumer, Endpoint endpoint, int
polledMessages)</code></li></ul></li><li><strong><code>rollback</code></strong><br
clear="none"><ul class="alternate"><li><code>boolean rollback(Consumer
consumer, Endpoint endpoint, int retryCounter, Exception e) throws
Exception</code></li></ul></li></ul><p>In <strong>Camel 2.3</strong>: the begin
method returns a <strong><code>boolean</code></strong> which indicates
whether or not to skipping polling. So you can implement your custom logic and
return <strong><code>false</code></strong> if you do not want to poll this
time.</p><p>In <strong>Camel 2.6</strong>: the commit method has an additional
parameter containing the number of message that was actually polled. For
example if there was no messages polled, the value would be zero, and you can
react accordingly.</p><p>The most interesting is the
<strong><code>rollback</code></strong> as it allows you do handle the caused
exception and decide what to do.</p><p>For instance i
f we want to provide a retry feature to a scheduled consumer we can implement
the <strong><code>PollingConsumerPollStrategy</code></strong> method and put
the retry logic in the <strong><code>rollback</code></strong> method. Lets just
retry up till three times:</p><parameter
ac:name="">java</parameter><plain-text-body>public boolean rollback(Consumer
consumer, Endpoint endpoint, int retryCounter, Exception e) throws Exception {
if (retryCounter < 3) {
// return true to tell Camel that it should retry the poll immediately
return true;
@@ -223,19 +94,12 @@ public static class MyCoolBean {
// okay we give up do not retry anymore
return false;
-}]]></script>
-</div></div><p>Notice that we are given the
<strong><code>Consumer</code></strong> as a parameter. We could use this to
<em>restart</em> the consumer as we can invoke stop and start:</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[// error occurred lets restart the consumer,
that could maybe resolve the issue
+}</plain-text-body><p>Notice that we are given the
<strong><code>Consumer</code></strong> as a parameter. We could use this to
<em>restart</em> the consumer as we can invoke stop and start:</p><parameter
ac:name="language">java</parameter><plain-text-body>// error occurred lets
restart the consumer, that could maybe resolve the issue
consumer.stop();
consumer.start();
-]]></script>
-</div></div><p><strong>Note:</strong> if you implement the
<strong><code>begin</code></strong> operation make sure to avoid throwing
exceptions as in such a case the <strong><code>poll</code></strong> operation
is not invoked and Camel will invoke the <strong><code>rollback</code></strong>
directly.</p><h4
id="PollingConsumer-ConfiguringantoUsePollingConsumerPollStrategy">Configuring
an <a shape="rect" href="endpoint.html">Endpoint</a> to Use
<code>PollingConsumerPollStrategy</code></h4><p>To configure an <a shape="rect"
href="endpoint.html">Endpoint</a> to use a custom
<strong><code>PollingConsumerPollStrategy</code></strong> you use the option
<strong><code>pollStrategy</code></strong>. For example in the file consumer
below we want to use our custom strategy defined in the <a shape="rect"
href="registry.html">Registry</a> with the bean id
<strong><code>myPoll</code></strong>:</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[from("file://inbox/?pollStrategy=#myPoll")
- .to("activemq:queue:inbox")
-]]></script>
-</div></div><p></p><h4 id="PollingConsumer-UsingThisPattern">Using This
Pattern</h4>
-
-<p>If you would like to use this EIP Pattern then please read the <a
shape="rect" href="getting-started.html">Getting Started</a>, you may also find
the <a shape="rect" href="architecture.html">Architecture</a> useful
particularly the description of <a shape="rect"
href="endpoint.html">Endpoint</a> and <a shape="rect"
href="uris.html">URIs</a>. Then you could try out some of the <a shape="rect"
href="examples.html">Examples</a> first before trying this pattern out.</p><h3
id="PollingConsumer-SeeAlso">See Also</h3><ul class="alternate"><li><a
shape="rect" href="pojo-consuming.html">POJO Consuming</a></li><li><a
shape="rect" href="batch-consumer.html">Batch Consumer</a></li></ul></div>
+</plain-text-body><p><strong>Note:</strong> if you implement the
<strong><code>begin</code></strong> operation make sure to avoid throwing
exceptions as in such a case the <strong><code>poll</code></strong> operation
is not invoked and Camel will invoke the <strong><code>rollback</code></strong>
directly.</p><h4
id="PollingConsumer-ConfiguringantoUsePollingConsumerPollStrategy">Configuring
an <a shape="rect" href="endpoint.html">Endpoint</a> to Use
<code>PollingConsumerPollStrategy</code></h4><p>To configure an <a shape="rect"
href="endpoint.html">Endpoint</a> to use a custom
<strong><code>PollingConsumerPollStrategy</code></strong> you use the option
<strong><code>pollStrategy</code></strong>. For example in the file consumer
below we want to use our custom strategy defined in the <a shape="rect"
href="registry.html">Registry</a> with the bean id
<strong><code>myPoll</code></strong>:</p><plain-text-body>from("file://inbox/?pollStrategy=#myPoll")
+ .to("activemq:queue:inbox")
+</plain-text-body><p><parameter ac:name=""><a shape="rect"
href="using-this-pattern.html">Using This Pattern</a></parameter></p><h3
id="PollingConsumer-SeeAlso">See Also</h3><ul class="alternate"><li><a
shape="rect" href="pojo-consuming.html">POJO Consuming</a></li><li><a
shape="rect" href="batch-consumer.html">Batch Consumer</a></li></ul></div>
</td>
<td valign="top">
<div class="navigation">
Modified: websites/production/camel/content/property.html
==============================================================================
--- websites/production/camel/content/property.html (original)
+++ websites/production/camel/content/property.html Fri Aug 25 08:22:01 2017
@@ -36,17 +36,6 @@
<![endif]-->
- <link href='//camel.apache.org/styles/highlighter/styles/shCoreCamel.css'
rel='stylesheet' type='text/css' />
- <link href='//camel.apache.org/styles/highlighter/styles/shThemeCamel.css'
rel='stylesheet' type='text/css' />
- <script src='//camel.apache.org/styles/highlighter/scripts/shCore.js'
type='text/javascript'></script>
- <script src='//camel.apache.org/styles/highlighter/scripts/shBrushJava.js'
type='text/javascript'></script>
- <script src='//camel.apache.org/styles/highlighter/scripts/shBrushXml.js'
type='text/javascript'></script>
- <script src='//camel.apache.org/styles/highlighter/scripts/shBrushPlain.js'
type='text/javascript'></script>
-
- <script type="text/javascript">
- SyntaxHighlighter.defaults['toolbar'] = false;
- SyntaxHighlighter.all();
- </script>
<title>
Apache Camel: Property
@@ -86,23 +75,8 @@
<tbody>
<tr>
<td valign="top" width="100%">
-<div class="wiki-content maincontent"><h2
id="Property-PropertyExpressionLanguage">Property Expression
Language</h2><p>The Property Expression Language allows you to extract values
of named exchange properties.</p><div class="confluence-information-macro
confluence-information-macro-note"><span class="aui-icon aui-icon-small
aui-iconfont-warning confluence-information-macro-icon"></span><div
class="confluence-information-macro-body"><p>From <strong>Camel 2.15</strong>
onwards the property language has been renamed to exchangeProperty to avoid
ambiguity, confusion and clash with properties as a general term. So use
exchangeProperty instead of property when using Camel 2.15
onwards.</p></div></div><p> </p><h3 id="Property-Exampleusage">Example
usage</h3><p>The recipientList element of the Spring DSL can utilize a property
expression like:</p><div class="code panel pdl" style="border-width: 1px;"><div
class="codeContent panelContent pdl">
-<script class="brush: xml; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-<route>
- <from uri="direct:a" />
- <recipientList>
- <exchangeProperty>myProperty</exchangeProperty>
- </recipientList>
-</route>
-]]></script>
-</div></div><p>In this case, the list of recipients are contained in the
property 'myProperty'.</p><p>And the same example in Java DSL:</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-from("direct:a").recipientList(property("myProperty"));
-]]></script>
-</div></div><p>And with a slightly different syntax where you use the builder
to the fullest (i.e. avoid using parameters but using stacked operations,
notice that property is not a parameter but a stacked method call)</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
from("direct:a").recipientList().property("myProperty");
-]]></script>
-</div></div><h3 id="Property-Dependencies">Dependencies</h3><p>The Property
language is part of <strong>camel-core</strong>.</p></div>
+<div class="wiki-content maincontent"><h2
id="Property-PropertyExpressionLanguage">Property Expression
Language</h2><p>The Property Expression Language allows you to extract values
of named exchange properties.</p><rich-text-body><p>From <strong>Camel
2.15</strong> onwards the property language has been renamed to
exchangeProperty to avoid ambiguity, confusion and clash with properties as a
general term. So use exchangeProperty instead of property when using Camel 2.15
onwards.</p></rich-text-body><p> </p><h3
id="Property-Exampleusage">Example usage</h3><p>The recipientList element of
the Spring DSL can utilize a property expression
like:</p><plain-text-body>{snippet:id=e1|lang=xml|url=camel/trunk/components/camel-spring/src/test/resources/org/apache/camel/spring/processor/recipientListWithStringDelimitedProperty.xml}</plain-text-body><p>In
this case, the list of recipients are contained in the property
'myProperty'.</p><p>And the same example in Java DSL:</p><plain-text-body>{
snippet:id=example|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/RecipientListWithStringDelimitedPropertyTest.java}</plain-text-body><p>And
with a slightly different syntax where you use the builder to the fullest
(i.e. avoid using parameters but using stacked operations, notice that property
is not a parameter but a stacked method call)</p><parameter
ac:name="">java</parameter><plain-text-body>
from("direct:a").recipientList().property("myProperty");
+</plain-text-body><h3 id="Property-Dependencies">Dependencies</h3><p>The
Property language is part of <strong>camel-core</strong>.</p></div>
</td>
<td valign="top">
<div class="navigation">
Modified: websites/production/camel/content/python.html
==============================================================================
--- websites/production/camel/content/python.html (original)
+++ websites/production/camel/content/python.html Fri Aug 25 08:22:01 2017
@@ -110,46 +110,19 @@
</choice>
</route>
]]></script>
-</div></div><p></p><h3
id="Python-ScriptContextOptions"><code>ScriptContext</code>
Options</h3><p> </p><div class="confluence-information-macro
confluence-information-macro-information"><span class="aui-icon aui-icon-small
aui-iconfont-info confluence-information-macro-icon"></span><div
class="confluence-information-macro-body">The <code>JSR-223</code>
scripting language's <strong><code>ScriptContext</code></strong> is
pre-configured with the following attributes all set at
<strong><code>ENGINE_SCOPE</code></strong>.</div></div><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Attribute</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>Type</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Value</p></th></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><span><code>camelContext</code><br
clear="none"></span></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><cod
e>org.apache.camel.CamelContext</code></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p>The Camel Context.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>context</code></p></td><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>org.apache.camel.CamelContext</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>The Camel Context (cannot be
used in groovy).</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>exchange</code></p></td><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>org.apache.camel.Exchange</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>The current
Exchange.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>properties</code></p></td><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>org.apache.camel.builder.script.PropertiesFunction</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.9:</strong> Fun
ction with a <strong><code>resolve</code></strong> method to make it easier to
use Camels <a shape="rect" href="properties.html">Properties</a> component from
scripts. See further below for example.</p></td></tr><tr><td colspan="1"
rowspan="1" class="confluenceTd"><p><code>request</code></p></td><td
colspan="1" rowspan="1"
class="confluenceTd"><p><code>org.apache.camel.Message</code></p></td><td
colspan="1" rowspan="1"
class="confluenceTd"><p>The <strong><code>IN</code></strong>
message.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>response</code></p></td><td colspan="1"
rowspan="1"
class="confluenceTd"><p><code>org.apache.camel.Message</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p><strong>Deprecated</strong>:
The <strong><code>OUT</code></strong> message.
The <strong><code>OUT</code></strong> message
is <strong><code>null</code></strong> by default. Use the
<strong><code>IN</code></strong> message instead.</p></
td></tr></tbody></table></div><p>See <a shape="rect"
href="scripting-languages.html">Scripting Languages</a> for the list of
languages with explicit DSL support.</p><h3
id="Python-PassingAdditionalArgumentstotheScriptingEngine">Passing Additional
Arguments to the <code>ScriptingEngine</code></h3><p><strong>Available
from Camel 2.8</strong></p><p>You can provide additional arguments to the
<strong><code>ScriptingEngine</code></strong> using a header on the Camel
message with the key
<strong><code>CamelScriptArguments</code></strong>.</p><p>Example:</p><div
class="code panel pdl" style="border-width: 1px;"><div class="codeContent
panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[
-public void testArgumentsExample() throws Exception {
- getMockEndpoint("mock:result").expectedMessageCount(0);
- getMockEndpoint("mock:unmatched").expectedMessageCount(1);
-
- // additional arguments to ScriptEngine
- Map<String, Object> arguments = new HashMap<String, Object>();
- arguments.put("foo", "bar");
- arguments.put("baz", 7);
-
- // those additional arguments is provided as a header on the Camel Message
- template.sendBodyAndHeader("direct:start", "hello",
ScriptBuilder.ARGUMENTS, arguments);
-
- assertMockEndpointsSatisfied();
-}
-]]></script>
-</div></div><h3 id="Python-UsingPropertiesFunction">Using Properties
Function</h3><p><strong>Available from Camel 2.9</strong></p><p>If you need to
use the <a shape="rect" href="properties.html">Properties</a> component from a
script to lookup property placeholders, then its a bit cumbersome to do so. For
example, to set a header name <strong><code>myHeader</code></strong> with
a value from a property placeholder, whose key is taken from a header named
<strong><code>foo</code></strong>.</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[.setHeader("myHeader").groovy("context.resolvePropertyPlaceholders('{{'
+ request.headers.get('foo') + '}}')")
-]]></script>
-</div></div><p>From <strong>Camel 2.9</strong>: you can now use the properties
function and the same example is simpler:</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[.setHeader("myHeader").groovy("properties.resolve(request.headers.get('foo'))")
-]]></script>
-</div></div><h3 id="Python-LoadingScriptFromExternalResource">Loading Script
From External Resource</h3><p><strong>Available from Camel
2.11</strong></p><p>You can externalize the script and have Camel load it from
a resource such as <strong><code>classpath:</code></strong>,
<strong><code>file:</code></strong>, or <strong><code>http:</code></strong>.
This is done using the following syntax:
<strong><code>resource:scheme:location</code></strong> e.g. to refer to a file
on the classpath you can do:</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: java; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[.setHeader("myHeader").groovy("resource:classpath:mygroovy.groovy")
-]]></script>
-</div></div><h3 id="Python-HowtoGettheResultfromMultipleStatementsScript">How
to Get the Result from Multiple Statements Script</h3><p><strong>Available from
Camel 2.14</strong></p><p>The script engine's eval method returns
a <strong><code>null</code></strong> when it runs a multi-statement
script. However, Camel can look up the value of a script's result by using the
key <strong><code>result</code></strong> from the value set. When writing a
multi-statement script set the value of
the <strong><code>result</code></strong> variable as the script return
value.</p><div class="code panel pdl" style="border-width: 1px;"><div
class="codeContent panelContent pdl">
-<script class="brush: text; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[bar = "baz";
+</div></div><p></p><h3
id="Python-ScriptContextOptions"><code>ScriptContext</code>
Options</h3><p> </p><rich-text-body>The <code>JSR-223</code>
scripting language's <strong><code>ScriptContext</code></strong> is
pre-configured with the following attributes all set at
<strong><code>ENGINE_SCOPE</code></strong>.</rich-text-body><div
class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1"
rowspan="1" class="confluenceTh"><p>Attribute</p></th><th colspan="1"
rowspan="1" class="confluenceTh"><p>Type</p></th><th colspan="1" rowspan="1"
class="confluenceTh"><p>Value</p></th></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><span><code>camelContext</code><br
clear="none"></span></p></td><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>org.apache.camel.CamelContext</code></p></td><td
colspan="1" rowspan="1" class="confluenceTd"><p>The Camel
Context.</p></td></tr><tr><td colspan="1" rowspan="1"
class="confluenceTd"><p><code>context</code
></p></td><td colspan="1" rowspan="1"
>class="confluenceTd"><p><code>org.apache.camel.CamelContext</code></p></td><td
> colspan="1" rowspan="1" class="confluenceTd"><p>The Camel Context (cannot be
>used in groovy).</p></td></tr><tr><td colspan="1" rowspan="1"
>class="confluenceTd"><p><code>exchange</code></p></td><td colspan="1"
>rowspan="1"
>class="confluenceTd"><p><code>org.apache.camel.Exchange</code></p></td><td
>colspan="1" rowspan="1" class="confluenceTd"><p>The current
>Exchange.</p></td></tr><tr><td colspan="1" rowspan="1"
>class="confluenceTd"><p><code>properties</code></p></td><td colspan="1"
>rowspan="1"
>class="confluenceTd"><p><code>org.apache.camel.builder.script.PropertiesFunction</code></p></td><td
> colspan="1" rowspan="1" class="confluenceTd"><p><strong>Camel 2.9:</strong>
>Function with a <strong><code>resolve</code></strong> method to make it
>easier to use Camels <a shape="rect" href="properties.html">Properties</a>
>component from scripts. See further below for example.</p></td
></tr><tr><td colspan="1" rowspan="1"
>class="confluenceTd"><p><code>request</code></p></td><td colspan="1"
>rowspan="1"
>class="confluenceTd"><p><code>org.apache.camel.Message</code></p></td><td
>colspan="1" rowspan="1"
>class="confluenceTd"><p>The <strong><code>IN</code></strong>
>message.</p></td></tr><tr><td colspan="1" rowspan="1"
>class="confluenceTd"><p><code>response</code></p></td><td colspan="1"
>rowspan="1"
>class="confluenceTd"><p><code>org.apache.camel.Message</code></p></td><td
>colspan="1" rowspan="1" class="confluenceTd"><p><strong>Deprecated</strong>:
>The <strong><code>OUT</code></strong> message.
>The <strong><code>OUT</code></strong> message
>is <strong><code>null</code></strong> by default. Use the
><strong><code>IN</code></strong> message
>instead.</p></td></tr></tbody></table></div><p>See <a shape="rect"
>href="scripting-languages.html">Scripting Languages</a> for the list of
>languages with explicit DSL support.</p><h3
>id="Python-PassingAdditionalArguments
totheScriptingEngine">Passing Additional Arguments to
the <code>ScriptingEngine</code></h3><p><strong>Available from Camel
2.8</strong></p><p>You can provide additional arguments to the
<strong><code>ScriptingEngine</code></strong> using a header on the Camel
message with the key
<strong><code>CamelScriptArguments</code></strong>.</p><p>Example:<plain-text-body>{snippet:id=e1|lang=java|url=camel/trunk/components/camel-script/src/test/java/org/apache/camel/builder/script/JavaScriptExpressionTest.java}</plain-text-body></p><h3
id="Python-UsingPropertiesFunction">Using Properties
Function</h3><p><strong>Available from Camel 2.9</strong></p><p>If you need to
use the <a shape="rect" href="properties.html">Properties</a> component from a
script to lookup property placeholders, then its a bit cumbersome to do so. For
example, to set a header name <strong><code>myHeader</code></strong> with
a value from a property placeholder, whose key is taken from a header named
<strong><code>f
oo</code></strong>.</p><plain-text-body>.setHeader("myHeader").groovy("context.resolvePropertyPlaceholders('{{'
+ request.headers.get('foo') + '}}')")
+</plain-text-body><p>From <strong>Camel 2.9</strong>: you can now use the
properties function and the same example is simpler:</p><parameter
ac:name="language">java</parameter><plain-text-body>.setHeader("myHeader").groovy("properties.resolve(request.headers.get('foo'))")
+</plain-text-body><h3 id="Python-LoadingScriptFromExternalResource">Loading
Script From External Resource</h3><p><strong>Available from Camel
2.11</strong></p><p>You can externalize the script and have Camel load it from
a resource such as <strong><code>classpath:</code></strong>,
<strong><code>file:</code></strong>, or <strong><code>http:</code></strong>.
This is done using the following syntax:
<strong><code>resource:scheme:location</code></strong> e.g. to refer to a file
on the classpath you can do:</p><parameter
ac:name="language">java</parameter><plain-text-body>.setHeader("myHeader").groovy("resource:classpath:mygroovy.groovy")
+</plain-text-body><h3
id="Python-HowtoGettheResultfromMultipleStatementsScript">How to Get the Result
from Multiple Statements Script</h3><p><strong>Available from Camel
2.14</strong></p><p>The script engine's eval method returns
a <strong><code>null</code></strong> when it runs a multi-statement
script. However, Camel can look up the value of a script's result by using the
key <strong><code>result</code></strong> from the value set. When writing a
multi-statement script set the value of
the <strong><code>result</code></strong> variable as the script return
value.</p><parameter ac:name="language">text</parameter><plain-text-body>bar =
"baz";
# some other statements ...
# camel take the result value as the script evaluation result
result = body * 2 + 1
-]]></script>
-</div></div><p> </p><h3 id="Python-Dependencies">Dependencies</h3><p>To
use scripting languages in your camel routes you need to add the a dependency
on <strong><code>camel-script</code></strong> which integrates the JSR-223
scripting engine.</p><p>If you use maven you could just add the following to
your <strong><code>pom.xml</code></strong>, substituting the version number for
the latest & greatest release (see <a shape="rect" href="download.html">the
download page for the latest versions</a>).</p><div class="code panel pdl"
style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<script class="brush: xml; gutter: false; theme: Default"
type="syntaxhighlighter"><![CDATA[<dependency>
+</plain-text-body><p> </p><h3
id="Python-Dependencies">Dependencies</h3><p>To use scripting languages in your
camel routes you need to add the a dependency on
<strong><code>camel-script</code></strong> which integrates the JSR-223
scripting engine.</p><p>If you use maven you could just add the following to
your <strong><code>pom.xml</code></strong>, substituting the version number for
the latest & greatest release (see <a shape="rect" href="download.html">the
download page for the latest versions</a>).</p><parameter
ac:name="">xml</parameter><plain-text-body><dependency>
<groupId>org.apache.camel</groupId>
<artifactId>camel-script</artifactId>
<version>x.x.x</version>
</dependency>
-]]></script>
-</div></div></div>
+</plain-text-body></div>
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