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-<div class="wiki-content maincontent"><div class="chapter" id="chapter-pattern-appendix"><h1 id="BookPatternAppendix-PatternAppendix">Pattern Appendix</h1><p>There now follows a breakdown of the various <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/toc.html" rel="nofollow">Enterprise Integration Patterns</a> that Camel supports</p><h2 id="BookPatternAppendix-MessagingSystems">Messaging Systems</h2><h3 id="BookPatternAppendix-MessageChannel">Message Channel</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/MessageChannel.html" rel="nofollow">Message Channel</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a>. The Message Channel is an internal implementation detail of the <a shape="rect" class="external-link" href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Endpoint.html">Endpoint</a> interface and all interac
tions with the Message Channel are via the Endpoint interfaces.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/MessageChannelSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/MessageChannelSolution.gif"></span></p><p><strong style="font-size: 16.0px;line-height: 1.5625;"><br clear="none"></strong></p><p><strong style="font-size: 16.0px;line-height: 1.5625;">Example</strong></p><p>In JMS, Message Channels are represented by topics and queues such as the following</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">jms:queue:foo</script>
- </div>
-</div><p> </p><p>This message channel can be then used within the <a shape="rect" href="jms.html">JMS</a> component</p><p><strong style="line-height: 1.4285715;">Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">to(&quot;jms:queue:foo&quot;)</script>
- </div>
-</div><p><strong><br clear="none"></strong></p><p><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></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">&lt;to uri=&quot;jms:queue:foo&quot;/&gt;</script>
- </div>
-</div><p> </p><p>For more details see</p><ul><li><a shape="rect" href="message.html">Message</a></li><li><a shape="rect" href="message-endpoint.html">Message Endpoint</a></li></ul><p></p><h4 id="BookPatternAppendix-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="BookPatternAppendix-Message">Message</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/Message.html" rel="nofollow">Message</a> from the <a shape="rect" href="enterprise-integration-pattern
s.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/Message.html">Message</a> interface. </p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/MessageSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/MessageSolution.gif"></span></p><p>To support various message <a shape="rect" href="exchange-pattern.html">exchange patterns</a> like one way <a shape="rect" href="event-message.html">Event Message</a> and <a shape="rect" href="request-reply.html">Request Reply</a> messages Camel uses an <a shape="rect" href="exchange.html">Exchange</a> interface which has a <strong>pattern</strong> property which can be set to <strong>InOnly</strong> for an <a shape="rect" href="event-message.html">Event Message</a> which has a single inbound Message, or
<strong>InOut</strong> for a <a shape="rect" href="request-reply.html">Request Reply</a> where there is an inbound and outbound message.</p><p>Here is a basic example of sending a Message to a route in <strong>InOnly</strong> and <strong>InOut</strong> modes</p><p><strong>Requestor 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"> //InOnly getContext().createProducerTemplate().sendBody(&quot;direct:startInOnly&quot;, &quot;Hello World&quot;); //InOut String result = (String) getContext().createProducerTemplate().requestBody(&quot;direct:startInOut&quot;, &quot;Hello World&quot;); </script>
- </div>
-</div><p><strong>Route Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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"> from(&quot;direct:startInOnly&quot;).inOnly(&quot;bean:process&quot;); from(&quot;direct:startInOut&quot;).inOut(&quot;bean:process&quot;); </script>
- </div>
-</div><p><strong>Route Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></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"> &lt;route&gt; &lt;from uri=&quot;direct:startInOnly&quot;/&gt; &lt;inOnly uri=&quot;bean:process&quot;/&gt; &lt;/route&gt; &lt;route&gt; &lt;from uri=&quot;direct:startInOut&quot;/&gt; &lt;inOut uri=&quot;bean:process&quot;/&gt; &lt;/route&gt; </script>
- </div>
-</div><h4 id="BookPatternAppendix-UsingThisPattern.1">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="BookPatternAppendix-PipesandFilters">Pipes and Filters</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/PipesAndFilters.html" rel="nofollow">Pipes and Filters</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> in various ways.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-exter
nal-resource" src="http://www.enterpriseintegrationpatterns.com/img/PipesAndFilters.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/PipesAndFilters.gif"></span></p><p>With Camel you can split your processing across multiple independent <a shape="rect" href="endpoint.html">Endpoint</a> instances which can then be chained together.</p><h4 id="BookPatternAppendix-UsingRoutingLogic">Using Routing Logic</h4><p>You can create pipelines of logic using multiple <a shape="rect" href="endpoint.html">Endpoint</a> or <a shape="rect" href="message-translator.html">Message Translator</a> instances as follows
- </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"> from(&quot;direct:a&quot;).pipeline(&quot;direct:x&quot;, &quot;direct:y&quot;, &quot;direct:z&quot;, &quot;mock:result&quot;); </script>
- </div>
- </div>Though pipeline is the default mode of operation when you specify multiple outputs in Camel. The opposite to pipeline is multicast; which fires the same message into each of its outputs. (See the example below).<p>In Spring XML you can use the <strong><code><pipeline/></code></strong> element</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">&lt;route&gt; &lt;from uri=&quot;activemq:SomeQueue&quot;/&gt; &lt;pipeline&gt; &lt;bean ref=&quot;foo&quot;/&gt; &lt;bean ref=&quot;bar&quot;/&gt; &lt;to uri=&quot;activemq:OutputQueue&quot;/&gt; &lt;/pipeline&gt; &lt;/route&gt; </script>
- </div>
-</div><p>In the above the pipeline element is actually unnecessary, you could use 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">&lt;route&gt; &lt;from uri=&quot;activemq:SomeQueue&quot;/&gt; &lt;bean ref=&quot;foo&quot;/&gt; &lt;bean ref=&quot;bar&quot;/&gt; &lt;to uri=&quot;activemq:OutputQueue&quot;/&gt; &lt;/route&gt; </script>
- </div>
-</div><p>which is a bit more explicit.</p><p>However if you wish to use <strong><code><multicast/></code></strong> to avoid a pipeline - to send the same message into multiple pipelines - then the <strong><code><pipeline/></code></strong> element comes into its own:</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">&lt;route&gt; &lt;from uri=&quot;activemq:SomeQueue&quot;/&gt; &lt;multicast&gt; &lt;pipeline&gt; &lt;bean ref=&quot;something&quot;/&gt; &lt;to uri=&quot;log:Something&quot;/&gt; &lt;/pipeline&gt; &lt;pipeline&gt; &lt;bean ref=&quot;foo&quot;/&gt; &lt;bean ref=&quot;bar&quot;/&gt; &lt;to uri=&quot;activemq:OutputQueue&quot;/&gt; &lt;/pipeline&gt; &lt;/multicast&gt; &lt;/route&gt; </script>
- </div>
-</div><p>In the above example we are routing from a single <a shape="rect" href="endpoint.html">Endpoint</a> to a list of different endpoints specified using <a shape="rect" href="uris.html">URIs</a>. If you find the above a bit confusing, try reading about the <a shape="rect" href="architecture.html">Architecture</a> or try the <a shape="rect" href="examples.html">Examples</a></p><p></p><h4 id="BookPatternAppendix-UsingThisPattern.2">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="BookPatternAppendix-MessageRouter">Message Router</h3
><p>The <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/MessageRouter.html" rel="nofollow">Message Router</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> allows you to consume from an input destination, evaluate some predicate then choose the right output destination.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/MessageRouter.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/MessageRouter.gif"></span></p><p>The following example shows how to route a request from an input <strong>queue:a</strong> endpoint to either <strong>queue:b</strong>, <strong>queue:c</strong> or <strong>queue:d</strong> depending on the evaluation of various <a shape="rect" href="predicate.html">Predicate</a> expressions</p><p><strong>Using the <a shape="rect" href="fluent-builders.
html">Fluent Builders</a></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"> RouteBuilder builder = new RouteBuilder() { public void configure() { errorHandler(deadLetterChannel(&quot;mock:error&quot;)); from(&quot;direct:a&quot;) .choice() .when(header(&quot;foo&quot;).isEqualTo(&quot;bar&quot;)) .to(&quot;direct:b&quot;) .when(header(&quot;foo&quot;).isEqualTo(&quot;cheese&quot;)) .to(&quot;direct:c&quot;) .otherwise() .to(&quot;direct:d&quot;); } }; </script>
- </div>
-</div><p><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></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"> &lt;camelContext errorHandlerRef=&quot;errorHandler&quot; xmlns=&quot;http://camel.apache.org/schema/spring&quot;&gt; &lt;route&gt; &lt;from uri=&quot;direct:a&quot;/&gt; &lt;choice&gt; &lt;when&gt; &lt;xpath&gt;$foo = &#39;bar&#39;&lt;/xpath&gt; &lt;to uri=&quot;direct:b&quot;/&gt; &lt;/when&gt; &lt;when&gt; &lt;xpath&gt;$foo = &#39;cheese&#39;&lt;/xpath&gt; &lt;to uri=&quot;direct:c&quot;/&gt; &lt;/when&gt; &lt;otherwise&gt; &lt;to uri=&quot;direct:d&quot;/&gt; &lt;/otherwise&gt; &lt;/choice&gt; &lt;/route&gt; &lt;/camelContext&gt; </script>
- </div>
-</div><h4 id="BookPatternAppendix-Choicewithoutotherwise">Choice without otherwise</h4><p>If you use a <code>choice</code> without adding an <code>otherwise</code>, any unmatched exchanges will be dropped by default. </p><h4 id="BookPatternAppendix-UsingThisPattern.3">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="BookPatternAppendix-MessageTranslator">Message Translator</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/MessageTranslator.html" rel="nofollow">Message Tran
slator</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> by using an arbitrary <a shape="rect" href="processor.html">Processor</a> in the routing logic, by using a <a shape="rect" href="bean-integration.html">bean</a> to perform the transformation, or by using transform() in the DSL. You can also use a <a shape="rect" href="data-format.html">Data Format</a> to marshal and unmarshal messages in different encodings.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/MessageTranslator.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/MessageTranslator.gif"></span></p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></strong></p><p>You can transform a message using Camel's <a shape="rect" href="bean-integration.html">Bean Integration</a> to call any method on a bean in yo
ur <a shape="rect" href="registry.html">Registry</a> such as your <a shape="rect" href="spring.html">Spring</a> XML configuration file as follows</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"> from(&quot;activemq:SomeQueue&quot;). beanRef(&quot;myTransformerBean&quot;, &quot;myMethodName&quot;). to(&quot;mqseries:AnotherQueue&quot;); </script>
- </div>
-</div><p>Where the "myTransformerBean" would be defined in a Spring XML file or defined in JNDI etc. You can omit the method name parameter from beanRef() and the <a shape="rect" href="bean-integration.html">Bean Integration</a> will try to deduce the method to invoke from the message exchange.</p><p>or you can add your own explicit <a shape="rect" href="processor.html">Processor</a> to do the transformation</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"> from(&quot;direct:start&quot;).process(new Processor() { public void process(Exchange exchange) { Message in = exchange.getIn(); in.setBody(in.getBody(String.class) + &quot; World!&quot;); } }).to(&quot;mock:result&quot;); </script>
- </div>
-</div><p>or you can use the DSL to explicitly configure the transformation</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"> from(&quot;direct:start&quot;).transform(body().append(&quot; World!&quot;)).to(&quot;mock:result&quot;); </script>
- </div>
-</div><p><strong>Use Spring XML</strong></p><p>You can also use <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a> to do a transformation. Basically any <a shape="rect" href="expression.html">Expression</a> language can be substituted inside the transform element as shown below</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"> &lt;camelContext xmlns=&quot;http://camel.apache.org/schema/spring&quot;&gt; &lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;transform&gt; &lt;simple&gt;${in.body} extra data!&lt;/simple&gt; &lt;/transform&gt; &lt;to uri=&quot;mock:end&quot;/&gt; &lt;/route&gt; &lt;/camelContext&gt; </script>
- </div>
-</div><p>Or you can use the <a shape="rect" href="bean-integration.html">Bean Integration</a> to invoke a bean</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"> &lt;route&gt; &lt;from uri=&quot;activemq:Input&quot;/&gt; &lt;bean ref=&quot;myBeanName&quot; method=&quot;doTransform&quot;/&gt; &lt;to uri=&quot;activemq:Output&quot;/&gt; &lt;/route&gt; </script>
- </div>
-</div><p>You can also use <a shape="rect" href="templating.html">Templating</a> to consume a message from one destination, transform it with something like <a shape="rect" href="velocity.html">Velocity</a> or <a shape="rect" href="xquery.html">XQuery</a> and then send it on to another destination. For example using InOnly (one way messaging)</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"> from(&quot;activemq:My.Queue&quot;). to(&quot;velocity:com/acme/MyResponse.vm&quot;). to(&quot;activemq:Another.Queue&quot;); </script>
- </div>
-</div><p>If you want to use InOut (request-reply) semantics to process requests on the <strong>My.Queue</strong> queue on <a shape="rect" href="activemq.html">ActiveMQ</a> with a template generated response, then sending responses back to the JMSReplyTo Destination you could use this.</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"> from(&quot;activemq:My.Queue&quot;). to(&quot;velocity:com/acme/MyResponse.vm&quot;); </script>
- </div>
-</div><h4 id="BookPatternAppendix-UsingThisPattern.4">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><ul class="alternate"><li><a shape="rect" href="content-enricher.html">Content Enricher</a></li><li><a shape="rect" href="using-getin-or-getout-methods-on-exchange.html">Using getIn or getOut methods on Exchange</a></li></ul><h3 id="BookPatternAppendix-MessageEndpoint">Message Endpoint</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/MessageEndpoint.html" rel="nofollow">Message
Endpoint</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/Endpoint.html">Endpoint</a> interface.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/MessageEndpointSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/MessageEndpointSolution.gif"></span></p><p>When using the <a shape="rect" href="dsl.html">DSL</a> to create <a shape="rect" href="routes.html">Routes</a> you typically refer to Message Endpoints by their <a shape="rect" href="uris.html">URIs</a> rather than directly using the <a shape="rect" class="external-link" href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Endpoint.html">Endpoint</a> interface. Its then a responsibility of
the <a shape="rect" class="external-link" href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/CamelContext.html">CamelContext</a> to create and activate the necessary Endpoint instances using the available <a shape="rect" class="external-link" href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/Component.html">Component</a> implementations.</p><h4 id="BookPatternAppendix-Example">Example</h4><p>The following example route demonstrates the use of a <a shape="rect" href="https://cwiki.apache.org/confluence/display/SM/File">File</a> Consumer Endpoint and <a shape="rect" href="jms.html">JMS</a> Producer Endpoint</p><p><strong><br clear="none"></strong></p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">from(&quot;file://local/router/messages/foo&quot;) .to(&quot;jms:queue:foo&quot;);</script>
- </div>
-</div><p> </p><p><strong><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></strong></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">&lt;route&gt; &lt;from uri=&quot;file://local/router/messages/foo&quot;/&gt; &lt;to uri=&quot;jms:queue:foo&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p> </p><h3 id="BookPatternAppendix-DynamicTo">Dynamic To</h3><p><strong>Available as of Camel 2.16</strong></p><p>There is a new <toD> that allows to send a message to a dynamic computed <a shape="rect" href="endpoint.html">Endpoint</a> using one or more <a shape="rect" href="expression.html">Expression</a> that are concat together. By default the <a shape="rect" href="simple.html">Simple</a> language is used to compute the endpoint. For example to send a message to a endpoint defined by a header you can do</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">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;toD uri=&quot;${header.foo}&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p>And 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">from(&quot;direct:start&quot;) .toD(&quot;${header.foo}&quot;);</script>
- </div>
-</div><p> </p><p>You can also prefix the uri with a value because by default the uri is evaluated using the <a shape="rect" href="simple.html">Simple</a> language</p><div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: xml; gutter: false; theme: Default" type="syntaxhighlighter">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;toD uri=&quot;mock:${header.foo}&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p>And 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">from(&quot;direct:start&quot;) .toD(&quot;mock:${header.foo}&quot;);</script>
- </div>
-</div><p>In the example above we compute an endpoint that has prefix "mock:" and then the header foo is appended. So for example if the header foo has value order, then the endpoint is computed as "mock:order".</p><p>You can also use other languages than <a shape="rect" href="simple.html">Simple</a> such as <a shape="rect" href="xpath.html">XPath</a> - this requires to prefix with language: as shown below (simple language is the default language). If you do not specify language: then the endpoint is a component name. And in some cases there is both a component and language with the same name such as xquery.</p><div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: xml; gutter: false; theme: Default" type="syntaxhighlighter">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;toD uri=&quot;language:xpath:/order/@uri&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p>This is done by specifying the name of the language followed by a colon.</p><div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: java; gutter: false; theme: Default" type="syntaxhighlighter">from(&quot;direct:start&quot;) .toD(&quot;language:xpath:/order/@uri&quot;);</script>
- </div>
-</div><p>You can also concat multiple <a shape="rect" href="language.html">Language</a>(s) together using the plus sign <code>+</code> such as shown below:</p><div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: xml; gutter: false; theme: Default" type="syntaxhighlighter">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;toD uri=&quot;jms:${header.base}+language:xpath:/order/@id&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p>In the example above the uri is a combination of <a shape="rect" href="simple.html">Simple</a> language and <a shape="rect" href="xpath.html">XPath</a> where the first part is simple (simple is default language). And then the plus sign separate to another language, where we specify the language name followed by a colon</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">from(&quot;direct:start&quot;) .toD(&quot;jms:${header.base}+language:xpath:/order/@id&quot;);</script>
- </div>
-</div><p>You can concat as many languages as you want, just separate them with the plus sign</p><p>The Dynamic To has a few options you can configure</p><div class="table-wrap">
- <table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh">Name</th><th colspan="1" rowspan="1" class="confluenceTh">Default Value</th><th colspan="1" rowspan="1" class="confluenceTh">Description</th></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">uri</td><td colspan="1" rowspan="1" class="confluenceTd"> </td><td colspan="1" rowspan="1" class="confluenceTd"><strong>Mandatory:</strong> The uri to use. See above</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">pattern</td><td colspan="1" rowspan="1" class="confluenceTd"> </td><td colspan="1" rowspan="1" class="confluenceTd">To set a specific <a shape="rect" href="exchange-pattern.html">Exchange Pattern</a> to use when sending to the endpoint. The original MEP is restored afterwards.</td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">cacheSize</td><td colspan="1" rowspan="1" class="confluenceTd"> </td><td colspan="1" rowspan="1" class="confluenceTd"><span
style="color: rgb(0,0,0);">Allows to configure the cache size for the </span><code>ProducerCache</code><span style="color: rgb(0,0,0);"> which caches producers for reuse. Will by default use the default cache size which is 1000. Setting the value to -1 allows to turn off the cache all together.</span></td></tr><tr><td colspan="1" rowspan="1" class="confluenceTd">ignoreInvalidEndpoint</td><td colspan="1" rowspan="1" class="confluenceTd"><code>false</code></td><td colspan="1" rowspan="1" class="confluenceTd"><span style="color: rgb(0,0,0);">Whether to ignore an endpoint URI that could not be resolved. If disabled, Camel will throw an exception identifying the invalid endpoint URI.</span></td></tr></tbody></table>
-</div><p> </p><p>For more details see</p><ul><li><a shape="rect" href="recipient-list.html">Recipient List</a></li><li><a shape="rect" href="message.html">Message</a></li><li><a shape="rect" href="wire-tap.html">Wire Tap</a><br clear="none"><br clear="none"></li></ul><p></p><h4 id="BookPatternAppendix-UsingThisPattern.5">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><h2 id="BookPatternAppendix-MessagingChannels">Messaging Channels</h2><h3 id="BookPatternAppendix-PointtoPointChannel">Point to Point Channel</h3><p>Camel supports the <a s
hape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/PointToPointChannel.html" rel="nofollow">Point to Point Channel</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> using the following components</p><ul><li><a shape="rect" href="seda.html">SEDA</a> for in-VM seda based messaging</li><li><a shape="rect" href="jms.html">JMS</a> for working with JMS Queues for high performance, clustering and load balancing</li><li><a shape="rect" href="jpa.html">JPA</a> for using a database as a simple message queue</li><li><a shape="rect" href="xmpp.html">XMPP</a> for point-to-point communication over XMPP (Jabber)</li><li>and others</li></ul><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/PointToPointSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/PointToPointSolution.gif"><
/span></p><p>The following example demonstrates point to point messaging using the <a shape="rect" href="jms.html">JMS</a> component </p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">from(&quot;direct:start&quot;) .to(&quot;jms:queue:foo&quot;);</script>
- </div>
-</div><p> </p><p><strong><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></strong></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">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;to uri=&quot;jms:queue:foo&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p> </p><p> </p><p></p><h4 id="BookPatternAppendix-UsingThisPattern.6">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="BookPatternAppendix-PublishSubscribeChannel">Publish Subscribe Channel</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/PublishSubscribeChannel.html" rel="nofollow">Publish Subscribe Channel</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> using for example the following components:</p><ul><li><a
shape="rect" href="jms.html">JMS</a> for working with JMS Topics for high performance, clustering and load balancing</li><li><a shape="rect" href="xmpp.html">XMPP</a> when using rooms for group communication</li><li><a shape="rect" href="seda.html">SEDA</a> for working with SEDA in the same <a shape="rect" href="camelcontext.html">CamelContext</a> which can work in pub-sub, but allowing multiple consumers.</li><li><a shape="rect" href="vm.html">VM</a> as SEDA but for intra-JVM.</li></ul><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/PublishSubscribeSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/PublishSubscribeSolution.gif"></span></p><h4 id="BookPatternAppendix-UsingRoutingLogic.1">Using Routing Logic</h4><p>Another option is to explicitly list the publish-subscribe relationship in your routing logic; this keeps the producer an
d consumer decoupled but lets you control the fine grained routing configuration using the <a shape="rect" href="dsl.html">DSL</a> or <a shape="rect" href="xml-configuration.html">Xml Configuration</a>.</p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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"> RouteBuilder builder = new RouteBuilder() { public void configure() { errorHandler(deadLetterChannel(&quot;mock:error&quot;)); from(&quot;direct:a&quot;) .multicast().to(&quot;direct:b&quot;, &quot;direct:c&quot;, &quot;direct:d&quot;); } }; </script>
- </div>
-</div><p><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></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"> &lt;camelContext errorHandlerRef=&quot;errorHandler&quot; xmlns=&quot;http://camel.apache.org/schema/spring&quot;&gt; &lt;route&gt; &lt;from uri=&quot;direct:a&quot;/&gt; &lt;multicast&gt; &lt;to uri=&quot;direct:b&quot;/&gt; &lt;to uri=&quot;direct:c&quot;/&gt; &lt;to uri=&quot;direct:d&quot;/&gt; &lt;/multicast&gt; &lt;/route&gt; &lt;/camelContext&gt; </script>
- </div>
-</div><h4 id="BookPatternAppendix-UsingThisPattern.7">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><h2 id="BookPatternAppendix-DeadLetterChannel">Dead Letter Channel</h2><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/DeadLetterChannel.html" rel="nofollow">Dead Letter Channel</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/a
pache/camel/processor/DeadLetterChannel.html">DeadLetterChannel</a> processor which is an <a shape="rect" href="error-handler.html">Error Handler</a>.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/DeadLetterChannelSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/DeadLetterChannelSolution.gif"></span></p><div class="confluence-information-macro confluence-information-macro-tip">
- <p class="title">Differences Between The DeadLetterChannel And The DefaultErrorHandler</p>
- <span class="aui-icon aui-icon-small aui-iconfont-approve confluence-information-macro-icon"></span>
- <div class="confluence-information-macro-body">
- <p>The <strong><code>DefaultErrorHandler</code></strong> does very little: it ends the Exchange immediately and propagates the thrown Exception back to the caller.</p>
- <p>The <strong><code>DeadLetterChannel</code></strong> lets you control behaviors including redelivery, whether to propagate the thrown Exception to the caller (the <strong><code>handled</code></strong> option), and where the (failed) Exchange should now be routed to.</p>
- <p>The <strong><code>DeadLetterChannel</code></strong> is also by default configured to not be verbose in the logs, so when a message is handled and moved to the dead letter endpoint, then there is nothing logged. If you want some level of logging you can use the various options on the redelivery policy / dead letter channel to configure this. For example if you want the message history then set <strong><code>logExhaustedMessageHistory=true</code></strong> (and <strong><code>logHandled=true</code></strong> for <strong>Camel 2.15.x</strong> or older).</p>
- <p>When the <strong><code>DeadLetterChannel</code></strong> moves a message to the dead letter endpoint, any new Exception thrown is by default handled by the dead letter channel as well. This ensures that the <strong><code>DeadLetterChannel</code></strong> will always succeed. From <strong>Camel 2.15</strong>: this behavior can be changed by setting the option <strong><code>deadLetterHandleNewException=false</code></strong>. Then if a new Exception is thrown, then the dead letter channel will fail and propagate back that new Exception (which is the behavior of the default error handler). When a new Exception occurs then the dead letter channel logs this at <strong><code>WARN</code></strong> level. This can be turned off by setting <strong><code>logNewException=false</code></strong>.</p>
- </div>
-</div><h3 id="BookPatternAppendix-Redelivery">Redelivery</h3><p>It is common for a temporary outage or database deadlock to cause a message to fail to process; but the chances are if its tried a few more times with some time delay then it will complete fine. So we typically wish to use some kind of redelivery policy to decide how many times to try redeliver a message and how long to wait before redelivery attempts.</p><p>The <a shape="rect" class="external-link" href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/processor/RedeliveryPolicy.html">RedeliveryPolicy</a> defines how the message is to be redelivered. You can customize things like</p><ul><li>The number of times a message is attempted to be redelivered before it is considered a failure and sent to the dead letter channel.</li><li>The initial redelivery timeout.</li><li>Whether or not exponential backoff is used, i.e., the time between retries increases using a backoff multiplier.</li><li>Whether
to use collision avoidance to add some randomness to the timings.</li><li>Delay pattern (see below for details).</li><li><strong>Camel 2.11:</strong> Whether to allow redelivery during stopping/shutdown.</li></ul><p>Once all attempts at redelivering the message fails then the message is forwarded to the dead letter queue.</p><h3 id="BookPatternAppendix-AboutMovingExchangetoDeadLetterQueueandUsinghandled()">About Moving Exchange to Dead Letter Queue and Using <strong><code>handled()</code></strong></h3><p><strong><code>handled()</code></strong> on <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a></p><p>When all attempts of redelivery have failed the <a shape="rect" href="exchange.html">Exchange</a> is moved to the dead letter queue (the dead letter endpoint). The exchange is then complete and from the client point of view it was processed. As such the <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> have handled the <a shape="rect" hr
ef="exchange.html">Exchange</a>.</p><p>For instance configuring the dead letter channel as:</p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">errorHandler(deadLetterChannel(&quot;jms:queue:dead&quot;) .maximumRedeliveries(3).redeliveryDelay(5000)); </script>
- </div>
-</div><p><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></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">&lt;route errorHandlerRef=&quot;myDeadLetterErrorHandler&quot;&gt; &lt;!-- ... --&gt; &lt;/route&gt; &lt;bean id=&quot;myDeadLetterErrorHandler&quot; class=&quot;org.apache.camel.builder.DeadLetterChannelBuilder&quot;&gt; &lt;property name=&quot;deadLetterUri&quot; value=&quot;jms:queue:dead&quot;/&gt; &lt;property name=&quot;redeliveryPolicy&quot; ref=&quot;myRedeliveryPolicyConfig&quot;/&gt; &lt;/bean&gt; &lt;bean id=&quot;myRedeliveryPolicyConfig&quot; class=&quot;org.apache.camel.processor.RedeliveryPolicy&quot;&gt; &lt;property name=&quot;maximumRedeliveries&quot; value=&quot;3&quot;/&gt; &lt;property name=&quot;redeliveryDelay&quot; value=&quot;5000&quot;/&gt; &lt;/bean&gt; </script>
- </div>
-</div><p>The <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> above will clear the caused exception <strong><code>setException(null)</code></strong>, by moving the caused exception to a property on the <a shape="rect" href="exchange.html">Exchange</a>, with the key <strong><code>Exchange.EXCEPTION_CAUGHT</code></strong>. Then the <a shape="rect" href="exchange.html">Exchange</a> is moved to the <strong><code>jms:queue:dead</code></strong> destination and the client will not notice the failure.</p><h3 id="BookPatternAppendix-AboutMovingExchangetoDeadLetterQueueandUsingtheOriginalMessage">About Moving Exchange to Dead Letter Queue and Using the Original Message</h3><p>The option <strong><code>useOriginalMessage</code></strong> is used for routing the original input message instead of the current message that potentially is modified during routing.</p><p>For instance if you have this route:</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"> from(&quot;jms:queue:order:input&quot;) .to(&quot;bean:validateOrder&quot;) .to(&quot;bean:transformOrder&quot;) .to(&quot;bean:handleOrder&quot;); </script>
- </div>
-</div><p>The route listen for JMS messages and validates, transforms and handle it. During this the <a shape="rect" href="exchange.html">Exchange</a> payload is transformed/modified. So in case something goes wrong and we want to move the message to another JMS destination, then we can configure our <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> with the <strong><code>useOriginalMessage</code></strong> option. But when we move the <a shape="rect" href="exchange.html">Exchange</a> to this destination we do not know in which state the message is in. Did the error happen in before the <strong><code>transformOrder</code></strong> or after? So to be sure we want to move the original input message we received from <strong><code>jms:queue:order:input</code></strong>. So we can do this by enabling the <strong><code>useOriginalMessage</code></strong> option 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">// will use original body errorHandler(deadLetterChannel(&quot;jms:queue:dead&quot;) .useOriginalMessage() .maximumRedeliveries(5) .redeliverDelay(5000); </script>
- </div>
-</div><p>Then the messages routed to the <strong><code>jms:queue:dead</code></strong> is the original input. If we want to manually retry we can move the JMS message from the failed to the input queue, with no problem as the message is the same as the original we received.</p><h3 id="BookPatternAppendix-OnRedelivery">OnRedelivery</h3><p>When <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> is doing redeliver its possible to configure a <a shape="rect" href="processor.html">Processor</a> that is executed just <strong>before</strong> every redelivery attempt. This can be used for the situations where you need to alter the message before its redelivered. See below for sample.</p><div class="confluence-information-macro confluence-information-macro-tip">
- <p class="title">onException and onRedeliver</p>
- <span class="aui-icon aui-icon-small aui-iconfont-approve confluence-information-macro-icon"></span>
- <div class="confluence-information-macro-body">
- <p>We also support for per <a shape="rect" href="exception-clause.html"><strong>onException</strong></a> to set an <strong><code>onRedeliver</code></strong>. That means you can do special on redelivery for different exceptions, as opposed to <strong><code>onRedelivery</code></strong> set on <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> can be viewed as a global scope.</p>
- </div>
-</div><h3 id="BookPatternAppendix-RedeliveryDefaultValues">Redelivery Default Values</h3><p>Redelivery is disabled by default.</p><p>The default redeliver policy will use the following values:</p><ul><li><strong><code>maximumRedeliveries=0</code></strong></li><li><strong><code>redeliverDelay=1000L</code></strong> (1 second)</li><li><strong><code>maximumRedeliveryDelay = 60 * 1000L</code></strong> (60 seconds)</li><li><strong><code>backOffMultiplier</code></strong> and <strong><code>useExponentialBackOff</code></strong> are ignored.</li><li><strong><code>retriesExhaustedLogLevel=LoggingLevel.ERROR</code></strong></li><li><strong><code>retryAttemptedLogLevel=LoggingLevel.DEBUG</code></strong></li><li>Stack traces are logged for exhausted messages, from <strong>Camel 2.2</strong>.</li><li>Handled exceptions are not logged, from <strong>Camel 2.3</strong>.</li><li><strong><code>logExhaustedMessageHistory</code></strong> is true for default error handler, and false for dead letter channe
l.</li><li><strong><code>logExhaustedMessageBody</code></strong> <strong>Camel 2.17:</strong> is disabled by default to avoid logging sensitive message body/header details. If this option is <strong><code>true</code></strong>, then <strong><code>logExhaustedMessageHistory</code></strong> must also be <strong><code>true</code></strong>.</li></ul><p>The maximum redeliver delay ensures that a delay is never longer than the value, default 1 minute. This can happen when <strong><code>useExponentialBackOff=true</code></strong>.</p><p>The <strong><code>maximumRedeliveries</code></strong> is the number of <strong>re</strong>-delivery attempts. By default Camel will try to process the exchange 1 + 5 times. 1 time for the normal attempt and then 5 attempts as redeliveries.<br clear="none"> Setting the <strong><code>maximumRedeliveries=-1 </code></strong>(or < <strong><code>-1</code></strong>) will then always redelivery (unlimited).<br clear="none"> Setting the
0;<strong><code>maximumRedeliveries=0</code></strong> will disable re-delivery.</p><p>Camel will log delivery failures at the <strong><code>DEBUG</code></strong> logging level by default. You can change this by specifying <strong><code>retriesExhaustedLogLevel</code></strong> and/or <strong><code>retryAttemptedLogLevel</code></strong>. See <a shape="rect" class="external-link" href="http://svn.apache.org/repos/asf/camel/trunk/camel-core/src/test/java/org/apache/camel/builder/ExceptionBuilderWithRetryLoggingLevelSetTest.java">ExceptionBuilderWithRetryLoggingLevelSetTest</a> for an example.</p><p>You can turn logging of stack traces on/off. If turned off Camel will still log the redelivery attempt. It's just much less verbose.</p><h4 id="BookPatternAppendix-RedeliverDelayPattern">Redeliver Delay Pattern</h4><p>Delay pattern is used as a single option to set a range pattern for delays. When a delay pattern is in use the following options no longer apply:</p><ul><li><strong><c
ode>delay</code></strong></li><li><strong><code>backOffMultiplier</code></strong></li><li><strong><code>useExponentialBackOff</code></strong></li><li><strong><code>useCollisionAvoidance</code></strong></li><li><strong><code>maximumRedeliveryDelay</code></strong></li></ul><p>The idea is to set groups of ranges using the following syntax: <strong><code>limit:delay;limit 2:delay 2;limit 3:delay 3;...;limit N:delay N</code></strong></p><p>Each group has two values separated with colon:</p><ul class="alternate"><li><strong><code>limit</code></strong> = upper limit</li><li><strong><code>delay</code></strong> = delay in milliseconds<br clear="none"> And the groups is again separated with semi-colon. The rule of thumb is that the next groups should have a higher limit than the previous group.</li></ul><p>Lets clarify this with an example:<br clear="none"> <strong><code>delayPattern=5:1000;10:5000;20:20000</code></strong></p><p>That gives us three groups:</p><ul class="alternate"><li><s
trong><code>5:1000</code></strong></li><li><strong><code>10:5000</code></strong></li><li><strong><code>20:20000</code></strong></li></ul><p>Resulting in these delays between redelivery attempts:</p><ul class="alternate"><li>Redelivery attempt number <strong><code>1..4 = 0ms</code></strong> (as the first group start with 5)</li><li>Redelivery attempt number <strong><code>5..9 = 1000ms</code></strong> (the first group)</li><li>Redelivery attempt number <strong><code>10..19 = 5000ms</code></strong> (the second group)</li><li>Redelivery attempt number <strong><code>20.. = 20000ms</code></strong> (the last group)</li></ul><p>Note: The first redelivery attempt is <strong><code>1</code></strong>, so the first group should start with <strong><code>1</code></strong> or higher.</p><p>You can start a group with limit <strong><code>1</code></strong> to e.g., have a starting delay: <strong><code>delayPattern=1:1000;5:5000</code></strong></p><ul class="alternate"><li
>Redelivery attempt number <strong><code>1..4 = 1000ms</code></strong> (the first group)</li><li>Redelivery attempt number <strong><code>5.. = 5000ms</code></strong> (the last group)</li></ul><p>There is no requirement that the next delay should be higher than the previous. You can use any delay value you like. For example with <strong><code>delayPattern=1:5000;3:1000</code></strong> we start with 5 sec delay and then later reduce that to <strong><code>1</code></strong> second.</p><h3 id="BookPatternAppendix-Redeliveryheader">Redelivery header</h3><p>When a message is redelivered the <a shape="rect" class="external-link" href="http://camel.apache.org/maven/camel-core/apidocs/org/apache/camel/processor/DeadLetterChannel.html">DeadLetterChannel</a> will append a customizable header to the message to indicate how many times its been redelivered. <br clear="none"> Before <strong>Camel 2.6</strong>: The header is <strong><code>CamelRedeliveryCounter</code></strong>, which
is also defined on the <strong><code>Exchange.REDELIVERY_COUNTER</code></strong>.<br clear="none"> From <strong>Camel 2.6</strong>: The header <strong><code>CamelRedeliveryMaxCounter</code></strong>, which is also defined on the <strong><code>Exchange.REDELIVERY_MAX_COUNTER</code></strong>, contains the maximum redelivery setting. This header is absent if you use <strong><code>retryWhile</code></strong> or have unlimited maximum redelivery configured.</p><p>And a boolean flag whether it is being redelivered or not (first attempt). The header <strong><code>CamelRedelivered</code></strong> contains a boolean if the message is redelivered or not, which is also defined on the <strong><code>Exchange.REDELIVERED</code></strong>.</p><h3 id="BookPatternAppendix-DynamicallyCalculatedDelayFromtheExchange">Dynamically Calculated Delay From the Exchange</h3><p>In <strong>Camel 2.9</strong> and <strong>2.8.2</strong>: The header is <strong><code>CamelRedeliveryDelay</code></strong
>, which is also defined on the <strong><code>Exchange.REDELIVERY_DELAY</code></strong>. If this header is absent, normal redelivery rules apply.</p><h4 id="BookPatternAppendix-WhichEndpointFailed">Which Endpoint Failed</h4><p><strong>Available as of Camel 2.1</strong></p><p>When Camel routes messages it will decorate the <a shape="rect" href="exchange.html">Exchange</a> with a property that contains the <strong>last</strong> endpoint Camel send the <a shape="rect" href="exchange.html">Exchange</a> to:</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">String lastEndpointUri = exchange.getProperty(Exchange.TO_ENDPOINT, String.class); </script>
- </div>
-</div><p>The <strong><code>Exchange.TO_ENDPOINT</code></strong> have the constant value <strong><code>CamelToEndpoint</code></strong>. This information is updated when Camel sends a message to any endpoint. So if it exists its the <strong>last</strong> endpoint which Camel send the Exchange to.</p><p>When for example processing the <a shape="rect" href="exchange.html">Exchange</a> at a given <a shape="rect" href="endpoint.html">Endpoint</a> and the message is to be moved into the dead letter queue, then Camel also decorates the Exchange with another property that contains that <strong>last</strong> endpoint:</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">String failedEndpointUri = exchange.getProperty(Exchange.FAILURE_ENDPOINT, String.class); </script>
- </div>
-</div><p>The <strong><code>Exchange.FAILURE_ENDPOINT</code></strong> have the constant value <strong><code>CamelFailureEndpoint</code></strong>.</p><p>This allows for example you to fetch this information in your dead letter queue and use that for error reporting. This is usable if the Camel route is a bit dynamic such as the dynamic <a shape="rect" href="recipient-list.html">Recipient List</a> so you know which endpoints failed.</p><p><strong>Note:</strong> this information is retained on the Exchange even if the message is subsequently processed successfully by a given endpoint only to fail, for example, in local <a shape="rect" href="bean.html">Bean</a> processing instead. So, beware that this is a hint that helps pinpoint errors.</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">from(&quot;activemq:queue:foo&quot;) .to(&quot;http://someserver/somepath&quot;) .beanRef(&quot;foo&quot;); </script>
- </div>
-</div><p>Now suppose the route above and a failure happens in the <code>foo</code> bean. Then the <strong><code>Exchange.TO_ENDPOINT</code></strong> and <strong><code>Exchange.FAILURE_ENDPOINT</code></strong> will still contain the value of <code><a shape="rect" class="external-link" href="http://someserver/somepath" rel="nofollow">http://someserver/somepath</a></code>.</p><h3 id="BookPatternAppendix-OnPrepareFailure"><code>OnPrepareFailure</code></h3><p><strong>Available as of Camel 2.16</strong></p><p>Before the exchange is sent to the dead letter queue, you can use <strong><code>onPrepare</code></strong> to allow a custom <strong><code>Processor</code></strong> to prepare the exchange, such as adding information why the Exchange failed.</p><p>For example, the following processor adds a header with the exception message:</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"> public static class MyPrepareProcessor implements Processor { @Override public void process(Exchange exchange) throws Exception { Exception cause = exchange.getProperty(Exchange.EXCEPTION_CAUGHT, Exception.class); exchange.getIn().setHeader(&quot;FailedBecause&quot;, cause.getMessage()); } }</script>
- </div>
-</div><p>Then configure the error handler to use the processor as follows:</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">errorHandler(deadLetterChannel(&quot;jms:dead&quot;).onPrepareFailure(new MyPrepareProcessor()));</script>
- </div>
-</div><p> </p><p>Configuring this from XML DSL is as follows:</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">&lt;bean id=&quot;myPrepare&quot; class=&quot;org.apache.camel.processor.DeadLetterChannelOnPrepareTest.MyPrepareProcessor&quot;/&gt; &lt;errorHandler id=&quot;dlc&quot; type=&quot;DeadLetterChannel&quot; deadLetterUri=&quot;jms:dead&quot; onPrepareFailureRef=&quot;myPrepare&quot;/&gt;</script>
- </div>
-</div><p> </p><p>The <strong><code>onPrepare</code></strong> is also available using the default error handler.</p><h3 id="BookPatternAppendix-WhichRouteFailed">Which Route Failed</h3><p><strong>Available as of Camel 2.10.4/2.11</strong></p><p>When Camel error handler handles an error such as <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> or using <a shape="rect" href="exception-clause.html">Exception Clause</a> with <strong><code>handled=true</code></strong>, then Camel will decorate the <a shape="rect" href="exchange.html">Exchange</a> with the route id where the error occurred.</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">String failedRouteId = exchange.getProperty(Exchange.FAILURE_ROUTE_ID, String.class); </script>
- </div>
-</div><p>The <strong><code>Exchange.FAILURE_ROUTE_ID</code></strong> have the constant value <strong><code>CamelFailureRouteId</code></strong>. This allows for example you to fetch this information in your dead letter queue and use that for error reporting.</p><h3 id="BookPatternAppendix-ControlifRedeliveryisAllowedDuringStopping/Shutdown">Control if Redelivery is Allowed During Stopping/Shutdown</h3><p><strong>Available as of Camel 2.11</strong></p><p>Before <strong>Camel 2.10</strong>, Camel would perform redelivery while stopping a route, or shutting down Camel. This has improved a bit in <strong>Camel 2.10</strong>: Camel will no longer perform redelivery attempts when shutting down aggressively, e.g., during <a shape="rect" href="graceful-shutdown.html">Graceful Shutdown</a> and timeout hit.</p><p>From <strong>Camel 2.11</strong>: there is a new option <strong><code>allowRedeliveryWhileStopping</code></strong> which you can use to control if redelivery is allowed or not; notice
that any in progress redelivery will still be executed. This option can only disallow any redelivery to be executed <em><strong>after</strong></em> the stopping of a route/shutdown of Camel has been triggered. If a redelivery is disallowed then a <strong><code>RejectedExcutionException</code></strong> is set on the <a shape="rect" href="exchange.html">Exchange</a> and the processing of the <a shape="rect" href="exchange.html">Exchange</a> stops. This means any consumer will see the <a shape="rect" href="exchange.html">Exchange</a> as failed due the <strong><code>RejectedExcutionException</code></strong>. The default value is <strong><code>true</code></strong> for backward compatibility.</p><p>For example, the following snippet shows how to do this with Java DSL and XML 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"> // this error handler will try up till 20 redelivery attempts with 1 second between. // however if we are stopping then do not allow any redeliver attempts. errorHandler(defaultErrorHandler() .allowRedeliveryWhileStopping(false) .maximumRedeliveries(20).redeliveryDelay(1000).retryAttemptedLogLevel(LoggingLevel.INFO)); from(&quot;seda:foo&quot;).routeId(&quot;foo&quot;) .to(&quot;mock:foo&quot;) .throwException(new IllegalArgumentException(&quot;Forced&quot;)); </script>
- </div>
- </div>And the sample sample with XML DSL
- <div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: xml; gutter: false; theme: Default" type="syntaxhighlighter"> &lt;!-- notice we use the errorHandlerRef attribute to refer to the error handler to use as default --&gt; &lt;camelContext errorHandlerRef=&quot;myErrorHandler&quot; xmlns=&quot;http://camel.apache.org/schema/spring&quot;&gt; &lt;!-- configure error handler, to redeliver up till 10 times, with 1 sec delay and if we are stopping then do not allow redeliveries, to stop faster --&gt; &lt;errorHandler id=&quot;myErrorHandler&quot; type=&quot;DefaultErrorHandler&quot;&gt; &lt;redeliveryPolicy maximumRedeliveries=&quot;20&quot; redeliveryDelay=&quot;1000&quot; allowRedeliveryWhileStopping=&quot;false&quot; retryAttemptedLogLevel=&quot;INFO&quot;/&gt; &lt;/errorHandler&gt; &lt;route id=&quot;foo&quot;&gt; &lt;from uri=&quot;seda:foo&quot;/&gt; &lt;to uri=&am
p;quot;mock:foo&quot;/&gt; &lt;throwException ref=&quot;forced&quot;/&gt; &lt;/route&gt; &lt;/camelContext&gt; </script>
- </div>
- </div><h3 id="BookPatternAppendix-Samples">Samples</h3><p>The following example shows how to configure the Dead Letter Channel configuration using the <a shape="rect" href="dsl.html">DSL</a>
- </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"> RouteBuilder builder = new RouteBuilder() { public void configure() { // using dead letter channel with a seda queue for errors errorHandler(deadLetterChannel(&quot;seda:errors&quot;)); // here is our route from(&quot;seda:a&quot;).to(&quot;seda:b&quot;); } }; </script>
- </div>
- </div>You can also configure the <a shape="rect" class="external-link" href="http://camel.apache.org/maven/current/camel-core/apidocs/org/apache/camel/processor/RedeliveryPolicy.html">RedeliveryPolicy</a> as this example shows
- <div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: java; gutter: false; theme: Default" type="syntaxhighlighter"> RouteBuilder builder = new RouteBuilder() { public void configure() { // configures dead letter channel to use seda queue for errors and use at most 2 redelveries // and exponential backoff errorHandler(deadLetterChannel(&quot;seda:errors&quot;).maximumRedeliveries(2).useExponentialBackOff()); // here is our route from(&quot;seda:a&quot;).to(&quot;seda:b&quot;); } }; </script>
- </div>
- </div><h3 id="BookPatternAppendix-HowCanIModifytheExchangeBeforeRedelivery?">How Can I Modify the Exchange Before Redelivery?</h3><p>We support directly in <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> to set a <a shape="rect" href="processor.html">Processor</a> that is executed <strong>before</strong> each redelivery attempt. When <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> is doing redeliver its possible to configure a <a shape="rect" href="processor.html">Processor</a> that is executed just <strong>before</strong> every redelivery attempt. This can be used for the situations where you need to alter the message before its redelivered. Here we configure the <a shape="rect" href="dead-letter-channel.html">Dead Letter Channel</a> to use our processor <strong><code>MyRedeliveryProcessor</code></strong> to be executed before each redelivery.
- </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"> // we configure our Dead Letter Channel to invoke // MyRedeliveryProcessor before a redelivery is // attempted. This allows us to alter the message before errorHandler(deadLetterChannel(&quot;mock:error&quot;).maximumRedeliveries(5) .onRedelivery(new MyRedeliverProcessor()) // setting delay to zero is just to make unit testing faster .redeliveryDelay(0L)); </script>
- </div>
- </div>And this is the processor <strong><code>MyRedeliveryProcessor</code></strong> where we alter the message.
- <div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: java; gutter: false; theme: Default" type="syntaxhighlighter"> // This is our processor that is executed before every redelivery attempt // here we can do what we want in the java code, such as altering the message public class MyRedeliverProcessor implements Processor { public void process(Exchange exchange) throws Exception { // the message is being redelivered so we can alter it // we just append the redelivery counter to the body // you can of course do all kind of stuff instead String body = exchange.getIn().getBody(String.class); int count = exchange.getIn().getHeader(Exchange.REDELIVERY_COUNTER, Integer.class); exchange.getIn().setBody(body + count); // the maximum redelivery was set to 5 int max = exchange.getIn().getHeader(Exchange.REDELIVERY_MAX_COUNTER, Integer.class); assertEquals(5, max); } } </script>
- </div>
- </div><h3 id="BookPatternAppendix-HowCanILogWhatCausedtheDeadLetterChanneltobeInvoked?">How Can I Log What Caused the Dead Letter Channel to be Invoked?</h3><p>You often need to know what went wrong that caused the Dead Letter Channel to be used and it does not offer logging for this purpose. So the Dead Letter Channel's endpoint can be set to a endpoint of our own (such as <strong><code>direct:deadLetterChannel</code></strong>). We write a route to accept this Exchange and log the Exception, then forward on to where we want the failed Exchange moved to (which might be a DLQ queue for instance). See also <a shape="rect" class="external-link" href="http://stackoverflow.com/questions/13711462/logging-camel-exceptions-and-sending-to-the-dead-letter-channel" rel="nofollow">http://stackoverflow.com/questions/13711462/logging-camel-exceptions-and-sending-to-the-dead-letter-channel</a></p><p></p><h4 id="BookPatternAppendix-UsingThisPattern.8">Using This Pattern</h4> <p>If you wo
uld 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><ul class="alternate"><li><a shape="rect" href="error-handler.html">Error Handler</a></li><li><a shape="rect" href="exception-clause.html">Exception Clause</a></li></ul><h3 id="BookPatternAppendix-GuaranteedDelivery">Guaranteed Delivery</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/GuaranteedMessaging.html" rel="nofollow">Guaranteed Delivery</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> using among others the following
components:</p><ul><li><a shape="rect" href="file2.html">File</a> for using file systems as a persistent store of messages</li><li><a shape="rect" href="jms.html">JMS</a> when using persistent delivery (the default) for working with JMS Queues and Topics for high performance, clustering and load balancing</li><li><a shape="rect" href="jpa.html">JPA</a> for using a database as a persistence layer, or use any of the many other database component such as <a shape="rect" href="sql.html">SQL</a>, <a shape="rect" href="jdbc.html">JDBC</a>, <a shape="rect" href="ibatis.html">iBATIS</a>/<a shape="rect" href="mybatis.html">MyBatis</a>, <a shape="rect" href="hibernate.html">Hibernate</a></li><li><a shape="rect" href="hawtdb.html">HawtDB</a> for a lightweight key-value persistent store</li></ul><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/GuaranteedMessagingSolution.gi
f" data-image-src="http://www.enterpriseintegrationpatterns.com/img/GuaranteedMessagingSolution.gif"></span></p><h4 id="BookPatternAppendix-Example.1">Example</h4><p>The following example demonstrates illustrates the use of <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/GuaranteedMessaging.html" rel="nofollow">Guaranteed Delivery</a> within the <a shape="rect" href="jms.html">JMS</a> component. By default, a message is not considered successfully delivered until the recipient has persisted the message locally guaranteeing its receipt in the event the destination becomes unavailable.</p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">from(&quot;direct:start&quot;) .to(&quot;jms:queue:foo&quot;);</script>
- </div>
-</div><p> </p><p><strong><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></strong></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">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;to uri=&quot;jms:queue:foo&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p></p><h4 id="BookPatternAppendix-UsingThisPattern.9">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="BookPatternAppendix-MessageBus">Message Bus</h3><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/PointToPointChannel.html" rel="nofollow">Message Bus</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a>. You could view Camel as a Message Bus itself as it allows producers and consumers to be decoupled.</p><p><span class="confluence
-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/MessageBusSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/MessageBusSolution.gif"></span></p><p>Folks often assume that a Message Bus is a JMS though so you may wish to refer to the <a shape="rect" href="jms.html">JMS</a> component for traditional MOM support.<br clear="none"> Also worthy of note is the <a shape="rect" href="xmpp.html">XMPP</a> component for supporting messaging over XMPP (Jabber)</p><p>Of course there are also ESB products such as <a shape="rect" class="external-link" href="http://servicemix.apache.org/home.html">Apache ServiceMix</a> which serve as full fledged message busses.<br clear="none"> You can interact with <a shape="rect" class="external-link" href="http://servicemix.apache.org/home.html">Apache ServiceMix</a> from Camel in many ways, but in particular you can use the <a shape="rec
t" href="nmr.html">NMR</a> or <a shape="rect" href="jbi.html">JBI</a> component to access the ServiceMix message bus directly.</p><p> </p><h4 id="BookPatternAppendix-Example.2">Example</h4><p>The following demonstrates how the Camel message bus can be used to communicate with consumers and producers</p><p><strong><br clear="none"></strong></p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">from(&quot;direct:start&quot;) .pollEnrich(&quot;file:inbox?fileName=data.txt&quot;) .to(&quot;jms:queue:foo&quot;);</script>
- </div>
-</div><p> </p><p><strong><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></strong></strong></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">&lt;route&gt; &lt;from uri=&quot;direct:start&quot;/&gt; &lt;pollEnrich uri=&quot;file:inbox?fileName=data.txt&quot;/&gt; &lt;to uri=&quot;jms:queue:foo&quot;/&gt; &lt;/route&gt;</script>
- </div>
-</div><p></p><h4 id="BookPatternAppendix-UsingThisPattern.10">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="BookPatternAppendix-MessageConstruction">Message Construction</h3><h2 id="BookPatternAppendix-EventMessage">Event Message</h2><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/EventMessage.html" rel="nofollow">Event Message</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> by supporting the <a shape="rect" href="exchange-patter
n.html">Exchange Pattern</a> on a <a shape="rect" href="message.html">Message</a> which can be set to <strong>InOnly</strong> to indicate a oneway event message. Camel <a shape="rect" href="components.html">Components</a> then implement this pattern using the underlying transport or protocols.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/EventMessageSolution.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/EventMessageSolution.gif"></span></p><p>The default behaviour of many <a shape="rect" href="components.html">Components</a> is InOnly such as for <a shape="rect" href="jms.html">JMS</a>, <a shape="rect" href="file2.html">File</a> or <a shape="rect" href="seda.html">SEDA</a></p><div class="confluence-information-macro confluence-information-macro-tip">
- <p class="title">Related</p>
- <span class="aui-icon aui-icon-small aui-iconfont-approve confluence-information-macro-icon"></span>
- <div class="confluence-information-macro-body">
- <p>See the related <a shape="rect" href="request-reply.html">Request Reply</a> message.</p>
- </div>
-</div><h3 id="BookPatternAppendix-ExplicitlyspecifyingInOnly">Explicitly specifying InOnly</h3><p>If you are using a component which defaults to InOut you can override the <a shape="rect" href="exchange-pattern.html">Exchange Pattern</a> for an endpoint using the pattern property.</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">foo:bar?exchangePattern=InOnly </script>
- </div>
-</div><p>From 2.0 onwards on Camel you can specify the <a shape="rect" href="exchange-pattern.html">Exchange Pattern</a> using the DSL.</p><p><strong>Using the <a shape="rect" href="fluent-builders.html">Fluent Builders</a></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">from(&quot;mq:someQueue&quot;). setExchangePattern(ExchangePattern.InOnly). bean(Foo.class); </script>
- </div>
-</div><p>or you can invoke an endpoint with an explicit pattern</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">from(&quot;mq:someQueue&quot;). inOnly(&quot;mq:anotherQueue&quot;); </script>
- </div>
-</div><p><strong>Using the <a shape="rect" href="spring-xml-extensions.html">Spring XML Extensions</a></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">&lt;route&gt; &lt;from uri=&quot;mq:someQueue&quot;/&gt; &lt;inOnly uri=&quot;bean:foo&quot;/&gt; &lt;/route&gt; </script>
- </div>
-</div><div class="code panel pdl" style="border-width: 1px;">
- <div class="codeContent panelContent pdl">
- <script class="brush: java; gutter: false; theme: Default" type="syntaxhighlighter">&lt;route&gt; &lt;from uri=&quot;mq:someQueue&quot;/&gt; &lt;inOnly uri=&quot;mq:anotherQueue&quot;/&gt; &lt;/route&gt; </script>
- </div>
-</div><p></p><h4 id="BookPatternAppendix-UsingThisPattern.11">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><h2 id="BookPatternAppendix-RequestReply">Request Reply</h2><p>Camel supports the <a shape="rect" class="external-link" href="http://www.enterpriseintegrationpatterns.com/RequestReply.html" rel="nofollow">Request Reply</a> from the <a shape="rect" href="enterprise-integration-patterns.html">EIP patterns</a> by supporting the <a shape="rect" href="exchange-pattern.html">Exchange Pattern</a> on a <a shape="rect" href="message.html">Mess
age</a> which can be set to <strong>InOut</strong> to indicate a request/reply. Camel <a shape="rect" href="components.html">Components</a> then implement this pattern using the underlying transport or protocols.</p><p><span class="confluence-embedded-file-wrapper"><img class="confluence-embedded-image confluence-external-resource" src="http://www.enterpriseintegrationpatterns.com/img/RequestReply.gif" data-image-src="http://www.enterpriseintegrationpatterns.com/img/RequestReply.gif"></span></p><p>For example when using <a shape="rect" href="jms.html">JMS</a> with InOut the component will by default perform these actions</p><ul><li>create by default a temporary inbound queue</li><li>set the JMSReplyTo destination on the request message</li><li>set the JMSCorrelationID on the request message</li><li>send the request message</li><li>consume the response and associate the inbound message to the request using the JMSCorrelationID (as you may be performing many concurrent request/respons
es).</li></ul><div class="confluence-information-macro confluence-information-macro-tip">
- <p class="title">Related</p>
- <span class="aui-icon aui-icon-small aui-iconfont-approve confluence-information-macro-icon"></span>
- <div class="confluence-information-macro-body">
- <p>See the related <a shape="rect" href="event-message.html">Event Message</a> message</p>
- </div>
-</div><h3 id="BookPatternAppendix-ExplicitlyspecifyingInOut">Explicitly specifying InOut</h3><p>When consuming messages from <a shape="rect" href="jms.html">JMS</a> a Request-Reply is indicated by the presence of the <strong>JMSReplyTo</strong> header.</p><p>You can explicitly force an endpoint to be in Request Reply mode by setting the exchange pattern on the URI. e.g.</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"> jms:MyQueue?exchangePattern=InOut </script>
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-</div><p>You can specify the exchange pattern in DSL rule or Spring configuration.</p><div class="code panel pdl" style="border-width: 1px;">
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- <script class="brush: java; gutter: false; theme: Default" type="syntaxhighlighter"> // Send to an endpoint using InOut from(&quot;direct:testInOut&quot;).inOut(&quot;mock:result&quot;); // Send to an endpoint using InOut from(&quot;direct:testInOnly&quot;).inOnly(&quot;mock:result&quot;); // Set the exchange pattern to InOut, then send it from direct:inOnly to mock:result endpoint from(&quot;direct:testSetToInOnlyThenTo&quot;) .setExchangePattern(ExchangePattern.InOnly) .to(&quot;mock:result&quot;); from(&quot;direct:testSetToInOutThenTo&quot;) .setExchangePattern(ExchangePattern.InOut) .to(&quot;mock:result&quot;); // Or we can pass the pattern as a parameter to the to() method from(&quot;direct:testToWithInOnlyParam&quot;).to(ExchangePattern.InOnly, &quot;mock:result&quot;); from(&quot;direct:testToWithInOutParam&quot;).to(ExchangePattern.InOut, &quot;mock:result&quot;); from(&qu
ot;direct:testToWithRobustInOnlyParam&quot;).to(ExchangePattern.RobustInOnly, &quot;mock:result&quot;); // Set the exchange pattern to InOut, then send it on from(&quot;direct:testSetExchangePatternInOnly&quot;) .setExchangePattern(ExchangePattern.InOnly).to(&quot;mock:result&quot;); </script>
- </div>
-</div><div class="code panel pdl" style="border-width: 1px;">
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