[[mvel-language]]
= MVEL Language
:page-source: components/camel-mvel/src/main/docs/mvel-language.adoc

*Since Camel 2.0*

Camel allows Mvel to be used as an Expression or
Predicate the DSL or
Xml Configuration.

You could use Mvel to create an Predicate in a
Message Filter or as an
Expression for a
Recipient List

You can use Mvel dot notation to invoke operations. If you for instance
have a body that contains a POJO that has a `getFamiliyName` method then
you can construct the syntax as follows:

[source,java]
----------------------------------------
"request.body.familyName"
   // or 
"getRequest().getBody().getFamilyName()"
----------------------------------------

== Mvel Options

// language options: START
The MVEL language supports 1 options, which are listed below.



[width="100%",cols="2,1m,1m,6",options="header"]
|===
| Name | Default | Java Type | Description
| trim | true | Boolean | Whether to trim the value to remove leading and trailing whitespaces and line breaks
|===
// language options: END
// spring-boot-auto-configure options: START
== Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

[source,xml]
----
<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-mvel-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>
----


The component supports 6 options, which are listed below.



[width="100%",cols="2,5,^1,2",options="header"]
|===
| Name | Description | Default | Type
| *camel.component.mvel.basic-property-binding* | Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | Boolean
| *camel.component.mvel.bridge-error-handler* | Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored. | false | Boolean
| *camel.component.mvel.enabled* | Whether to enable auto configuration of the mvel component. This is enabled by default. |  | Boolean
| *camel.component.mvel.lazy-start-producer* | Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel's routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing. | false | Boolean
| *camel.language.mvel.enabled* | Whether to enable auto configuration of the mvel language. This is enabled by default. |  | Boolean
| *camel.language.mvel.trim* | Whether to trim the value to remove leading and trailing whitespaces and line breaks | true | Boolean
|===
// spring-boot-auto-configure options: END


== Variables

[width="100%",cols="10%,10%,80%",options="header",]
|=======================================================================
|Variable |Type |Description

|*this* |Exchange |the Exchange is the root object

|exchange |Exchange |the Exchange object

|exception |Throwable |the Exchange exception (if any)

|exchangeId |String |the exchange id

|fault |Message |the Fault message (if any)

|request |Message |the exchange.in message

|response |Message |the exchange.out message (if any)

|properties |Map |the exchange properties

|property(name) |Object |the property by the given name

|property(name, type) |Type |the property by the given name as the given type
|=======================================================================

== Samples

For example you could use Mvel inside a xref:manual::filter-eip.adoc[Message
Filter] in XML

[source,java]
---------------------------------------------
<route>
  <from uri="seda:foo"/>
  <filter>
    <mvel>request.headers.foo == 'bar'</mvel>
    <to uri="seda:bar"/>
  </filter>
</route>
---------------------------------------------

And the sample using Java DSL:

[source,java]
---------------------------------------------------------------------------------
   from("seda:foo").filter().mvel("request.headers.foo == 'bar'").to("seda:bar");
---------------------------------------------------------------------------------

== Loading script from external resource

*Since Camel 2.11*

You can externalize the script and have Camel load it from a resource
such as `"classpath:"`, `"file:"`, or `"http:"`. +
 This is done using the following syntax: `"resource:scheme:location"`,
eg to refer to a file on the classpath you can do:

[source,java]
-------------------------------------------------------------
.setHeader("myHeader").mvel("resource:classpath:script.mvel")
-------------------------------------------------------------

== Dependencies

To use Mvel in your camel routes you need to add the a dependency on
*camel-mvel* which implements the Mvel language.

If you use maven you could just add the following to your pom.xml,
substituting the version number for the latest & greatest release (see
the download page for the latest versions).

[source,java]
-------------------------------------
<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-mvel</artifactId>
  <version>x.x.x</version>
</dependency>
-------------------------------------
