Content Enricher

Camel supports the Content Enricher from the EIP patterns using a Message Translator, an arbitrary Processor in the routing logic, or using the enrich DSL element to enrich the message.

Content enrichment using a Message Translator or a Processor

Using the Fluent Builders

You can use Templating to consume a message from one destination, transform it with something like Velocity or XQuery, and then send it on to another destination. For example using InOnly (one way messaging)

If you want to use InOut (request-reply) semantics to process requests on the My.Queue queue on ActiveMQ with a template generated response, then sending responses back to the JMSReplyTo Destination you could use this:

Here is a simple example using the DSL directly to transform the message body{snippet:id=example|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TransformViaDSLTest.java}In this example we add our own Processor using explicit Java code{snippet:id=example|lang=java|url=camel/trunk/camel-core/src/test/java/org/apache/camel/processor/TransformTest.java}Finally we can use Bean Integration to use any Java method on any bean to act as the transformer

For further examples of this pattern in use you could look at one of the JUnit tests

• TransformTest
• TransformViaDSLTest

Using Spring XML

enrich-dsl

Content enrichment using the enrich DSL element

Camel comes with two flavors of content enricher in the DSL

• enrich
• pollEnrich

enrich uses a Producer to obtain the additional data. It is usually used for Request Reply messaging, for instance to invoke an external web service.
pollEnrich on the other hand uses a Polling Consumer to obtain the additional data. It is usually used for Event Message messaging, for instance to read a file or download a FTP file.

Enrich Options

Using the Fluent Builders

The content enricher (enrich) retrieves additional data from a resource endpoint in order to enrich an incoming message (contained in the original exchange). An aggregation strategy is used to combine the original exchange and the resource exchange. The first parameter of the AggregationStrategy.aggregate(Exchange, Exchange) method corresponds to the the original exchange, the second parameter the resource exchange. The results from the resource endpoint are stored in the resource exchange's out-message. Here's an example template for implementing an aggregation strategy:

Using this template the original exchange can be of any pattern. The resource exchange created by the enricher is always an in-out exchange.

Using Spring XML

The same example in the Spring DSL (Camel 2.15 or older)

The same example in the Spring DSL (Camel 2.16 or newer)

Aggregation strategy is optional

The aggregation strategy is optional. If you do not provide it Camel will by default just use the body obtained from the resource.

In the route above the message sent to the direct:result endpoint will contain the output from the direct:resource as we do not use any custom aggregation.

And for Spring DSL (Camel 2.15 or older) just omit the strategyRef attribute:

And for Spring DSL (Camel 2.16 or newer) just omit the strategyRef attribute:

Using dynamic uris

Available as of Camel 2.16

From Camel 2.16 onwards enrich and pollEnrich supports using dynamic uris computed based on information from the current Exchange. For example to enrich from a HTTP endpoint where the header with key orderId is used as part of the content-path of the HTTP url:

And in XML DSL

Content enrichment using pollEnrich

The pollEnrich works just as the enrich however as it uses a Polling Consumer we have 3 methods when polling

• receive
• receiveNoWait
• receive(timeout)

PollEnrich Options

If there is no data then the newExchange in the aggregation strategy is null.

You can pass in a timeout value that determines which method to use

• if timeout is -1 or other negative number then receive is selected (Important: the receive method may block if there is no message)
• if timeout is 0 then receiveNoWait is selected
• otherwise receive(timeout) is selected

The timeout values is in millis.

Example

In this example we enrich the message by loading the content from the file named inbox/data.txt.

And in XML DSL (Camel 2.15 or older) you do:

And in XML DSL (Camel 2.16 or newer) you do:

If there is no file then the message is empty. We can use a timeout to either wait (potentially forever) until a file exists, or use a timeout to wait a certain period.

For example to wait up to 5 seconds you can do (Camel 2.15 or older):

For example to wait up to 5 seconds you can do (Camel 2.16 or newer):

Using dynamic uris

Available as of Camel 2.16

From Camel 2.16 onwards enrich and pollEnrich supports using dynamic uris computed based on information from the current Exchange. For example to pollEnrich from an endpoint that uses a header to indicate a SEDA queue name:

And in XML DSL

Using This Pattern