[[ContentEnricher-ContentEnricher]]
= Content Enricher

Camel supports the
http://www.enterpriseintegrationpatterns.com/DataEnricher.html[Content
Enricher] from the xref:enterprise-integration-patterns.adoc[EIP
patterns] using a xref:message-translator.adoc[Message Translator], an
arbitrary xref:manual:ROOT:processor.adoc[Processor] in the routing logic, or using
the xref:content-enricher.adoc[enrich] DSL element to enrich the
message.

image::eip/DataEnricher.gif[image]

[[ContentEnricher-ContentenrichmentusingaMessageTranslatororaProcessor]]
== Content enrichment using a Message Translator or a Processor

You can consume a message from
one destination, transform it with something like
xref:ROOT:velocity-component.adoc[Velocity] or xref:ROOT:xquery-component.adoc[XQuery], and then send
it on to another destination. For example using InOnly (one way
messaging)

[source,java]
----
from("activemq:My.Queue")
    .to("velocity:com/acme/MyResponse.vm")
    .to("activemq:Another.Queue");
----

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

[source,java]
----
from("activemq:My.Queue")
    .to("velocity:com/acme/MyResponse.vm");
----

Here is a simple example using the xref:manual:ROOT:dsl.adoc[DSL] directly to
transform the message

[source,java]
----
from("direct:start")
    .setBody(body().append(" World!"))
    .to("mock:result");
----

In this example we add our own xref:manual:ROOT:processor.adoc[Processor] using
explicit Java

[source,java]
----
from("direct:start")
    .process(new Processor() {
        public void process(Exchange exchange) {
            Message in = exchange.getIn();
            in.setBody(in.getBody(String.class) + " World!");
        }
    })
    .to("mock:result");
----

we can use xref:manual:ROOT:bean-integration.adoc[Bean Integration] to use any Java
method on any bean to act as the transformer

[source,java]
----
from("activemq:My.Queue")
    .beanRef("myBeanName", "myMethodName")
    .to("activemq:Another.Queue");
----

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

* https://github.com/apache/camel/blob/main/core/camel-core/src/test/java/org/apache/camel/processor/TransformTest.java[TransformTest]
* https://github.com/apache/camel/blob/main/core/camel-core/src/test/java/org/apache/camel/processor/TransformViaDSLTest.java[TransformViaDSLTest]

*Using Spring XML*

[source,xml]
----
<route>
    <from uri="activemq:Input"/>
    <bean ref="myBeanName" method="doTransform"/>
    <to uri="activemq:Output"/>
</route>
----

[[ContentEnricher-ContentenrichmentusingtheenrichDSLelement]]
== 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 xref:requestReply-eip.adoc[Request Reply] messaging, for instance
to invoke an external web service. +
`pollEnrich` on the other hand uses a xref:polling-consumer.adoc[Polling
Consumer] to obtain the additional data. It is usually used for
xref:event-message.adoc[Event Message] messaging, for instance to read a
file or download a xref:ROOT:ftp-component.adoc[FTP] file.

Camel 2.15 or older - Data from current Exchange not used

`pollEnrich` or `enrich` does *not* access any data from the current
xref:manual:ROOT:exchange.adoc[Exchange] which means when polling it cannot use any
of the existing headers you may have set on the
xref:manual:ROOT:exchange.adoc[Exchange]. For example you cannot set a filename in
the `Exchange.FILE_NAME` header and use `pollEnrich` to consume only
that file. For that you *must* set the filename in the endpoint URI.

Instead of using `enrich` you can use xref:recipientList-eip.adoc[Recipient
List] and have dynamic endpoints and define an `AggregationStrategy` on
the xref:recipientList-eip.adoc[Recipient List] which then would work as a
`enrich` would do.

pollEnrich only accept one message as response. That means that if you
target to enrich your original message with the enricher collecting
messages from a seda, ... components using an aggregation strategy. Only
one response message will be aggregated with the original message.

From *Camel 2.16* onwards both enrich and pollEnrich supports dynamic
endpoints that uses an xref:manual:ROOT:expression.adoc[Expression] to compute the
uri, which allows to use data from the current
xref:manual:ROOT:exchange.adoc[Exchange]. In other words all what is told above no
longer apply and it just works.

[[ContentEnricher-EnrichOptions]]
== Enrich Options

[width="100%",cols="34%,33%,33%",options="header",]
|=======================================================================
|Name |Default Value |Description
|`uri` |  |The endpoint uri for the external service to enrich from. You
must use either `uri` or `ref`. *Important:* From Camel 2.16 onwards,
this option is removed, and you use an xref:manual:ROOT:expression.adoc[Expression]
to configure the uri, such as xref:components:languages:simple-language.adoc[Simple] or
xref:components:languages:constant-language.adoc[Constant] or any other dynamic language that can
compute the uri dynamically using values from the current
xref:manual:ROOT:exchange.adoc[Exchange].

|`ref` |  |Refers to the endpoint for the external service to enrich
from. You must use either `uri` or `ref`.  **Important:** From Camel
2.16 onwards, this option is removed, and you use an
xref:manual:ROOT:expression.adoc[Expression] to configure the uri, such as
xref:components:languages:simple-language.adoc[Simple] or xref:components:languages:constant-language.adoc[Constant] or any other
dynamic language that can compute the uri dynamically using values from
the current  xref:manual:ROOT:exchange.adoc[Exchange].

|expression |  |*Camel 2.16:* Mandatory.
The xref:manual:ROOT:expression.adoc[Expression] to configure the uri, such as
xref:components:languages:simple-language.adoc[Simple] or xref:components:languages:constant-language.adoc[Constant] or any other
dynamic language that can compute the uri dynamically using values from
the current  xref:manual:ROOT:exchange.adoc[Exchange].

|`strategyRef` |  |Refers to an
https://github.com/apache/camel/blob/main/core/camel-api/src/main/java/org/apache/camel/AggregationStrategy.java[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. From *Camel 2.12* onwards you can also use
a POJO as the `AggregationStrategy`, see the
xref:aggregate-eip.adoc[Aggregate] page for more details.

|`strategyMethodName` |  |*Camel 2.12:* This option can be used to
explicit declare the method name to use, when using POJOs as the
`AggregationStrategy`. See the xref:aggregate-eip.adoc[Aggregate] page for
more details.

|`strategyMethodAllowNull` |`false` |*Camel 2.12:* 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`. See the xref:aggregate-eip.adoc[Aggregate] page for
more details.

|`aggregateOnException` |`false` |*Camel 2.14:* 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.

|`shareUnitOfWork` |`false` |*Camel 2.16:*  Shares the unit of work 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. See
xref:split-eip.adoc[Splitter] for more information and example.

|`cacheSize` |  |*Camel 2.16:* Allows to configure the cache size for
the `ProducerCache` which caches producers for reuse in the enrich. Will
by default use the default cache size which is 1000. Setting the value
to -1 allows to turn off the cache all together.

|`ignoreInvalidEndpoint` |`false` |**Camel 2.16:** Whether to ignore an
endpoint URI that could not be resolved. If disabled, Camel will throw
an exception identifying the invalid endpoint URI.
|=======================================================================

[source,java]
----
AggregationStrategy aggregationStrategy = ... 

from("direct:start")
    .enrich("direct:resource", aggregationStrategy)
    .to("direct:result");

from("direct:resource") ...
----

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 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:

[source,java]
----
public class ExampleAggregationStrategy implements AggregationStrategy {

    public Exchange aggregate(Exchange original, Exchange resource) {
        Object originalBody = original.getIn().getBody();
        Object resourceResponse = resource.getIn().getBody();
        Object mergeResult = ... // combine original body and resource response

        if (original.getPattern().isOutCapable()) {
            original.getOut().setBody(mergeResult);
        } else {
            original.getIn().setBody(mergeResult);
        }

        return original;
    }
}
----

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

[source,xml]
----
<camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route>
        <from uri="direct:start"/>
        <enrich strategyRef="aggregationStrategy">
            <constant>direct:resource</constant>
        </enrich>
        <to uri="direct:result"/>
    </route>
    <route>
        <from uri="direct:resource"/>
        ...
    </route>
</camelContext>

<bean id="aggregationStrategy" class="..." />
----

[[ContentEnricher-Aggregationstrategyisoptional]]
=== 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.

[source,java]
----
from("direct:start")
    .enrich("direct:resource")
    .to("direct:result");
----

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:

[source,xml]
----
<route>
    <from uri="direct:start"/>
    <enrich>
        <constant>direct:resource</constant>
    </enrich>
    <to uri="direct:result"/>
</route>
----

[[ContentEnricher-Usingdynamicuris]]
=== Using dynamic uris

*Since Camel 2.16*

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

[source,java]
----
from("direct:start")
    .enrich().simple("http:myserver/$\{header.orderId}/order")
    .to("direct:result");
----

And in XML DSL

[source,xml]
----
<route>
    <from uri="direct:start"/>
    <enrich>
        <simple>http:myserver/$\{header.orderId}/order</simple>
    </enrich>
    <to uri="direct:result"/>
</route>
----

[[ContentEnricher-ContentenrichmentusingpollEnrich]]
=== Content enrichment using `pollEnrich`

The `pollEnrich` works just as the `enrich` however as it uses a
xref:polling-consumer.adoc[Polling Consumer] we have 3 methods when
polling

* receive
* receiveNoWait
* receive(timeout)

[[ContentEnricher-PollEnrichOptions]]
=== PollEnrich Options

[width="100%",cols="34%,33%,33%",options="header",]
|=======================================================================
|Name |Default Value |Description
|`uri` |  |The endpoint uri for the external service to enrich from. You
must use either `uri` or `ref`. **Important:** From Camel 2.16 onwards,
this option is removed, and you use an xref:manual:ROOT:expression.adoc[Expression]
to configure the uri, such as xref:components:languages:simple-language.adoc[Simple] or
xref:components:languages:constant-language.adoc[Constant] or any other dynamic language that can
compute the uri dynamically using values from the current
 xref:manual:ROOT:exchange.adoc[Exchange].

|`ref` |  |Refers to the endpoint for the external service to enrich
from. You must use either `uri` or `ref`. **Important:** From Camel 2.16
onwards, this option is removed, and you use an
xref:manual:ROOT:expression.adoc[Expression] to configure the uri, such as
xref:components:languages:simple-language.adoc[Simple] or xref:components:languages:constant-language.adoc[Constant] or any other
dynamic language that can compute the uri dynamically using values from
the current  xref:manual:ROOT:exchange.adoc[Exchange].

|`expression` |  |**Camel 2.16:** Mandatory.
The xref:manual:ROOT:expression.adoc[Expression] to configure the uri, such as
xref:components:languages:simple-language.adoc[Simple] or xref:components:languages:constant-language.adoc[Constant] or any other
dynamic language that can compute the uri dynamically using values from
the current xref:manual:ROOT:exchange.adoc[Exchange].

|`strategyRef` |  |Refers to an
https://github.com/apache/camel/blob/main/core/camel-api/src/main/java/org/apache/camel/AggregationStrategy.java[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. From *Camel 2.12* onwards you can also use
a POJO as the `AggregationStrategy`, see the
xref:aggregate-eip.adoc[Aggregate] page for more details.

|`strategyMethodName` |  |*Camel 2.12:* This option can be used to
explicit declare the method name to use, when using POJOs as the
`AggregationStrategy`. See the xref:aggregate-eip.adoc[Aggregate] page for
more details.

|`strategyMethodAllowNull` |`false` |*Camel 2.12:* 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`. See the xref:aggregate-eip.adoc[Aggregate] page for
more details.

|`timeout` |`-1` |Timeout in millis when polling from the external
service. See below for important details about the timeout.

|`aggregateOnException` |`false` |*Camel 2.14:* 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.

|`cacheSize` |  |*Camel 2.16:* Allows to configure the cache size for
the `ConsumerCache` which caches consumers for reuse in the pollEnrich.
Will by default use the default cache size which is 1000. Setting the
value to -1 allows to turn off the cache all together.

|`ignoreInvalidEndpoint` |`false` |**Camel 2.16:** Whether to ignore an
endpoint URI that could not be resolved. If disabled, Camel will throw
an exception identifying the invalid endpoint URI.
|=======================================================================

Good practice to use timeout value

By default Camel will use the `receive`. Which may block until there is
a message available. It is therefore recommended to always provide a
timeout value, to make this clear that we may wait for a message, until
the timeout is hit.

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.

Camel 2.15 or older - Data from current Exchange not used

`pollEnrich` does *not* access any data from the current
xref:manual:ROOT:exchange.adoc[Exchange] which means when polling it cannot use any
of the existing headers you may have set on the
xref:manual:ROOT:exchange.adoc[Exchange]. For example you cannot set a filename in
the `Exchange.FILE_NAME` header and use `pollEnrich` to consume only
that file. For that you *must* set the filename in the endpoint URI.

From **Camel 2.16** onwards both enrich and pollEnrich supports dynamic
endpoints that uses an xref:manual:ROOT:expression.adoc[Expression] to compute the
uri, which allows to use data from the current
xref:manual:ROOT:exchange.adoc[Exchange]. In other words all what is told above no
longer apply and it just works.

[[ContentEnricher-Example]]
==== Example

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

[source,java]
----
from("direct:start")
    .pollEnrich("file:inbox?fileName=data.txt")
    .to("direct:result");
----

And in XML DSL you do:

[source,xml]
----
<route>
    <from uri="direct:start"/>
    <pollEnrich>
        <constant>file:inbox?fileName=data.txt</constant>
    </pollEnrich>
    <to uri="direct:result"/>
</route>
----

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:

[source,xml]
----
<route>
    <from uri="direct:start"/>
    <pollEnrich timeout="5000">
        <constant>file:inbox?fileName=data.txt</constant>
    </pollEnrich>
    <to uri="direct:result"/>
</route>
----

[[ContentEnricher-Usingdynamicuris.1]]
==== Using dynamic uris

*Since Camel 2.16*

From Camel 2.16 onwards enrich and pollEnrich supports using dynamic
uris computed based on information from the
current xref:manual:ROOT:exchange.adoc[Exchange]. For example to pollEnrich from an
endpoint that uses a header to indicate a xref:ROOT:seda-component.adoc[SEDA] queue
name:

[source,java]
----
from("direct:start")
    .pollEnrich()
    .simple("seda:$\{header.name}")
    .to("direct:result");
----

And in XML DSL

[source,xml]
----
<route>
    <from uri="direct:start"/>
    <pollEnrich>
        <simple>seda:$\{header.name}</simple>
    </pollEnrich>
    <to uri="direct:result"/>
</route>
----

