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A number of production-ready Camel Routes and projects in fcrepo-camel-toolbox. Below are some additional Camel Routes to get you started.

LDPath Transformations

Using the fcrepo-ldpath Camel component, you can generate a JSON representation of a container and send it to a low-latency, highly available document store, such as Riak. The following route determines if a container has been removed or simply added/updated. It then routes the message appropriately to a load-balancer sitting in front of the Riak HTTP endpoint.

Camel route to populate a Riak store, using the Scala DSL

 

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val riakKeyProcessor  = (exchange : Exchange)  = > {
     exchange.getIn.setHeader(
         Exchange.HTTP _ PATH,
         "/buckets/fcrepo/keys/" + URLEncoder.encode(exchange.getIn.getHeader( "org.fcrepo.jms.identifier" , classOf[String]))
     )
}
 
"activemq:topic:fedora" == > {
     choice() {
         when( _ .in( "org.fcrepo.jms.eventType" == "http://fedora.info/definitions/v4/repository#NODE_REMOVED" ) {
             setHeader(Exchange.HTTP _ METHOD, constant( "DELETE" ))
             process(riakKeyProcessor)
             to( "http4:localhost:8098" )
         }
         otherwise() {
             to( "fcrepo:localhost:8080/fedora/rest" )
             filter(xpathFilter) {
                 to( "fcrepo:localhost:8080/fedora/rest?accept=application/json&transform=mytransform" )
                 setHeader(Exchange.HTTP _ METHOD, constant( "PUT" ))
                 process(riakKeyProcessor)
                 to( "http4:localhost:8098" )
             }
         }
     }
}

 

External Triplestore

Some additional processing must be done to transform an application/n-triples response into a validapplication/sparql-update payload before sending to an external triplestore such as Fuseki or Sesame. The fcrepo component contains some processors in org.fcrepo.camel.processor to handle this case. The examples below assume that messages have already been routed based on eventType (see below) and passed to the appropriate queue.

Populate an external triplestore

 

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from( "direct:delete" )
   .process( new SparqlDescribeProcessor())
   .to( "http4:localhost:3030/db/query" )
   .process( new SparqlDeleteProcessor())
   .to( "http4:localhost:3030/db/update" );
 
from( "direct:new" )
  .to( "fcrepo:localhost:8080/rest" )
  .process( new SparqlInsertProcessor())
  .to( "http4:localhost:3030/db/update" );
 
from( "direct:update" )
   .to( "fcrepo:localhost:8080/rest" )
   .process( new SparqlUpdateProcessor())
   .to( "http4:localhost:3030/db/update" );

 

Event-based Routing

It is often helpful to route messages to different queues based on the eventType value. This example splits messages oneventType values and routes the messages to appropriate queues. Following this example, it would be prudent to aggregate the messages based on org.fcrepo.jms.identifier value after retrieving the messages from the downstream queues.

Content-based Routing

 

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< route id = "fcrepo-event-splitter" >
     < description >
         Retrieve messages from the fedora topic. Event types are comma-delimited, so split them into separate messages before routing them.
     </ description >
     < from uri = "activemq:topic:fedora" />
     < setBody >
         < simple >${header.org.fcrepo.jms.eventType}</ simple >
     </ setBody >
     < split >
         < tokenize token = "," />
         < setHeader headerName = "org.fcrepo.jms.eventType" >
             < simple >${body}</ simple >
         </ setHeader >
         < setBody >
             < simple >null</ simple >
         </ setBody >
         < to uri = "seda:fcrepo-event-router" />
     </ split >
</ route >
 
< route id = "fcrepo-event-router" >
     < description >
         Route messages based on the eventType.
     </ description >
     < from uri = "seda:fcrepo-event-router" />
     < choice >
         < when >
             < simple >${header.org.fcrepo.jms.eventType} == "http://fedora.info/definitions/v4/repository#NODE_REMOVED"</ simple >
             < to uri = "activemq:queue:fcrepo.delete" />
         </ when >
         < when >
             < simple >${header.org.fcrepo.jms.eventType} == "http://fedora.info/definitions/v4/repository#NODE_ADDED"</ simple >
             < to uri = "activemq:queue:fcrepo.add" />
         </ when >
         < when >
             < simple >${header.org.fcrepo.jms.eventType} == "http://fedora.info/definitions/v4/repository#PROPERTY_ADDED"</ simple >
             < to uri = "activemq:queue:fcrepo.update" />
         </ when >
         < when >
             < simple >${header.org.fcrepo.jms.eventType} == "http://fedora.info/definitions/v4/repository#PROPERTY_CHANGED"</ simple >
             < to uri = "activemq:queue:fcrepo.update" />
         </ when >
         < when >
             < simple >${header.org.fcrepo.jms.eventType} == "http://fedora.info/definitions/v4/repository#PROPERTY_REMOVED"</ simple >
             < to uri = "activemq:queue:fcrepo.update" />
         </ when >
         < otherwise >
             < log message = "No router for ${header.org.fcrepo.jms.eventType}" />
         </ otherwise >
     </ choice >
</ route >

 

 

 

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