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XPathBuilder xpath = new XPathBuilder("/rdf:RDF/rdf:Description/rdf:type[@rdf:resource='http://fedora.info/definitions/v4/indexing#Indexable']")
xpath.namespace("rdf", "http://www.w3.org/1999/02/22-rdf-syntax-ns#")

from("activemq:topic:fedora")
  .to("fcrepo:localhost:8080/fedora/rest")
  .filter(xpath)
    .to("fcrepo:localhost:8080/fedora/rest?transform=default")
    .to("http4:localhost:8080/solr/core/update");

In this specific case, the XPath filtering predicate is just an example; you can, of course, use many different Predicate languages, including XQuery, SQL or various Scripting Languages.

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<route>
  <from uri="activemq:topic:fedora"/>
  <to uri="fcrepo:localhost:8080/fedora/rest"/>
  <filter>
    <xpath>/rdf:RDF/rdf:Description/rdf:type[@rdf:resource='http://fedora.info/definitions/v4/indexing#Indexable']</xpath>
    <to uri="fcrepo:localhost:8080/fedora/rest?transform=default"/>
    <to uri="http4:localhost:8080/solr/core/update"/>
  </filter>
</route>

Or, in Scala:

val xpath = new XPathBuilder("/rdf:RDF/rdf:Description/rdf:type[@rdf:resource='http://fedora.info/definitions/v4/indexing#Indexable']")
xpath.namespace("rdf", "http://www.w3.org/1999/02/22-rdf-syntax-ns#")
 
"activemq:topic:fedora" ==> {
    to("fcrepo:localhost:8080/fedora/rest")
    filter(xpath) {
        to("fcrepo:localhost:8080/fedora/rest?transform=default")
        to("http4:localhost:8080/solr/core/update")
    }
}

Please note that the hostnames used for Fedora and Solr in the snippets above are arbitrary. It is quite likely that these systems will be deployed on separate hosts and that the Camel routes will be deployed on yet another host. Camel makes it easy to distribute applications and replicate data asynchronously across an arbitrarily large number of independent systems.

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<destinationInterceptors>
  <virtualDestinationInterceptor>
    <virtualDestinations>
      <compositeTopic name="fedora">
        <forwardTo>
          <queue physicalName="fedora"/>
        </forwardTo>
      </compositeTopic>
    </virtualDestinations>
  </virtualDestinationInterceptor>
</destinationInterceptors>

<destinationInterceptors>
  <virtualDestinationInterceptor>
    <virtualDestinations>
      <compositeTopic name="fedora" forwardOnly="false">
        <forwardTo>
          <queue physicalName="fedora"/>
        </forwardTo>
      </compositeTopic>
    </virtualDestinations>
  </virtualDestinationInterceptor>
</destinationInterceptors>

<networkConnectors>
  <networkConnector name="fedora_bridge" dynamicOnly="true" uri="static:(tcp://remote-host:61616)">
    <dynamicallyIncludedDestinations>
      <topic physicalName="fedora"/>
      <queue physicalName="fedora"/>
    </dynamicallyIncludedDestinations>
  </networkConnector>
</networkConnectors>

ActiveMQ brokers support a wide variety of protocols. If Fedora's internal broker is bridged to an external broker, please remember to enable the proper protocols on the remote broker. This can be done like so:

<transportConnectors>
  <transportConnector name="openwire" uri="tcp://0.0.0.0:61616"/>
  <transportConnector name="stomp" uri="stomp://0.0.0.0:61613"/>
</transportConnectors>

Each transportConnector supports many additional options that can be added to this configuration.

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Camel routes can be deployed in any JVM container. In order to deploy to Jetty or Tomcat, the route must be built as a WAR file. This command will get you started:

$> mvn archetype:generate \
  -DarchetypeGroupId=org.apache.camel.archetypes \
  -DarchetypeArtifactId=camel-archetype-war \
  -DarchetypeVersion=2.14.0 \
  -DgroupId=org.example.camel \
  -DartifactId=my-camel-route \
  -Dversion=1.0.0-SNAPSHOT \
  -Dpackage=org.example.camel

After the project has been built (mvn install), you will find the WAR file in ./target. That file can simply be copied to the webapps directory of your Jetty/Tomcat server.

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1. downloading Karaf 4.x or later from an apache.org mirror
2. running ./bin/karaf to enter the shell

3. installing required bundles:
   

   Code Block
   language bash title Karaf console
   $> feature:repo-add camel 2.16.2 $> feature:repo-add activemq 5.11.1 $> feature:install camel $> feature:install activemq-camel # display available camel features $> feature:list | grep camel # install camel features, as needed $> feature:install camel-http4   # install fcrepo-camel (as of v4.4.0) $> feature:repo-add mvn:org.fcrepo.camel/fcrepo-camel/4.4.0/xml/features $> feature:install fcrepo-camel

   
   

4. setting up a service wrapper (so that karaf runs as a system-level service)
   

   Code Block
   language bash title Karaf console
   $> feature:install wrapper $> wrapper:install

   
   

5. following the directions provided by this command

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# install fcrepo-camel-toolbox (as of v4.1.0)
$> feature:repo-add mvn:org.fcrepo.camel/fcrepo-camel-toolbox/4.1.0/xml/features
 
# install fcrepo-camel-toolbox (as of v4.5.0)
$> feature:repo-add mvn:org.fcrepo.camel/toolbox-features/4.5.0/xml/features
 
# display available features
$> feature:list | grep fcrepo
 
# install feature
$> feature:install fcrepo-indexing-triplestore

Monitoring Your Camel Routes

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$> feature:repo-add hawtio 1.4.29
$> feature:install hawtio

Once deployed, hawtio is available at http://localhost:8181/hawtio/

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