[[mvel-language]]
= MVEL Language
//THIS FILE IS COPIED: EDIT THE SOURCE FILE:
:page-source: components/camel-mvel/src/main/docs/mvel-language.adoc
:docTitle: MVEL
:artifactId: camel-mvel
:description: Evaluate an MVEL template against the Camel Exchange.
:since: 2.0
:supportLevel: Stable

*Since Camel {since}*

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


== 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:{eip-vc}:eips: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>
-------------------------------------

include::camel-spring-boot::page$mvel-starter.adoc[]
