Enrich

Camel supports the Content Enricher from the EIP patterns.

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In Camel the Content Enricher can be done in several ways:

The most natural Camel approach is using Enrich EIP, which comes as two kinds:

  • Enrich EIP - This is the most common content enricher that uses a Producer to obtain the data. It is usually used for Request Reply messaging, for instance to invoke an external web service.

  • Poll Enrich EIP - 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.

This page documents the Enrich EIP.

The Enrich eip supports 8 options, which are listed below.

Name Description Default Type

expression

Required Expression that computes the endpoint uri to use as the resource endpoint to enrich from.

ExpressionDefinition

aggregationStrategy

Sets the AggregationStrategy to be used to merge the reply from the external service, into a single outgoing message. By default Camel will use the reply from the external service as outgoing message.

AggregationStrategy

aggregationStrategyMethodName

This option can be used to explicit declare the method name to use, when using POJOs as the AggregationStrategy.

String

aggregationStrategyMethodAllowNull

If this option is false then the aggregate method is not used if there was no data to enrich. If this option is true then null values is used as the oldExchange (when no data to enrich), when using POJOs as the AggregationStrategy.

String

aggregateOnException

If this option is false then the aggregate method is not used if there was an exception thrown while trying to retrieve the data to enrich from the resource. Setting this option to true allows end users to control what to do if there was an exception in the aggregate method. For example to suppress the exception or set a custom message body etc.

Boolean

shareUnitOfWork

Shares the org.apache.camel.spi.UnitOfWork with the parent and the resource exchange. Enrich will by default not share unit of work between the parent exchange and the resource exchange. This means the resource exchange has its own individual unit of work.

Boolean

cacheSize

Sets the maximum size used by the org.apache.camel.spi.ProducerCache which is used to cache and reuse producer when uris are reused. Beware that when using dynamic endpoints then it affects how well the cache can be utilized. If each dynamic endpoint is unique then its best to turn of caching by setting this to -1, which allows Camel to not cache both the producers and endpoints; they are regarded as prototype scoped and will be stopped and discarded after use. This reduces memory usage as otherwise producers/endpoints are stored in memory in the caches. However if there are a high degree of dynamic endpoints that have been used before, then it can benefit to use the cache to reuse both producers and endpoints and therefore the cache size can be set accordingly or rely on the default size (1000). If there is a mix of unique and used before dynamic endpoints, then setting a reasonable cache size can help reduce memory usage to avoid storing too many non frequent used producers.

Integer

ignoreInvalidEndpoint

Ignore the invalidate endpoint exception when try to create a producer with that endpoint.

Boolean

allowOptimisedComponents

Whether to allow components to optimise enricher if they are org.apache.camel.spi.SendDynamicAware .

true

Boolean

description

Sets the description of this node.

DescriptionDefinition

Content enrichment using Enrich EIP

Enrich EIP is the most common content enricher that uses a Producer to obtain the data.

The content enricher (enrich) retrieves additional data from a resource endpoint in order to enrich an incoming message (contained in the original exchange).

An AggregationStrategy is used to combine the original exchange and the resource exchange. The first parameter of the AggregationStrategy.aggregate(Exchange, Exchange) method corresponds to the original exchange, the second parameter the resource exchange.

Here’s an example for implementing an AggregationStrategy, which merges the two data together as a String with colon separator:

public class ExampleAggregationStrategy implements AggregationStrategy {

    public Exchange aggregate(Exchange newExchange, Exchange oldExchange) {
        // this is just an example, for real-world use-cases the
        // aggregation strategy would be specific to the use-case

        if (newExchange == null) {
            return oldExchange;
        }
        Object oldBody = oldExchange.getIn().getBody();
        Object newBody = newExchange.getIn().getBody();
        oldExchange.getIn().setBody(oldBody + ":" + newBody);
        return oldExchange;
    }

}

You then use the AggregationStrategy with the enrich in the Java DSL as shown:

AggregationStrategy aggregationStrategy = ...

from("direct:start")
  .enrich("http:remoteserver/foo", aggregationStrategy)
  .to("mock:result");

In the example Camel will call the http endpoint to collect some data, that will then be merged with the original message using the AggregationStrategy.

In XML DSL you use enrich as follows:

<bean id="myStrategy" class="com.foo.ExampleAggregationStrategy"/>

<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
  <route>
    <from uri="direct:start"/>
    <enrich aggregationStrategy="myStrategy">
      <constant>http:remoteserver/foo</constant>
    </enrich>
    <to uri="mock:result"/>
  </route>
</camelContext>

Aggregation Strategy is optional

The aggregation strategy is optional. If not provided then Camel will just use the result exchange as the result.

The following example:

from("direct:start")
  .enrich("http:remoteserver/foo")
  .to("direct:result");

And in XML:

<route>
    <from uri="direct:start"/>
    <enrich>
        <constant>http:remoteserver/foo</constant>
    </enrich>
    <to uri="mock:result"/>
</route>

Would be the same as using to:

from("direct:start")
  .to("http:remoteserver/foo")
  .to("direct:result");

Using dynamic uris

Both 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:

from("direct:start")
  .enrich().simple("http:myserver/${header.orderId}/order")
  .to("direct:result");

And in XML DSL:

<route>
  <from uri="direct:start"/>
  <enrich>
    <simple>http:myserver/${header.orderId}/order</simple>
  </enrich>
  <to uri="direct:result"/>
</route>
See the cacheSize option for more details on how much cache to use depending on how many or few unique endpoints are used.

Using out of the box Aggregation Strategies

The org.apache.camel.builder.AggregationStrategies is a builder that can be used for creating commonly used aggregation strategies without having to create a class.

For example the ExampleAggregationStrategy from previously can be built as follows:

AggregationStrategy agg = AggregationStrategies.string(":");

There are many other possibilities with the AggregationStrategies builder, and for more details see the AggregationStrategies javadoc.

See More

See Poll Enrich EIP

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