[[mvel-language]]
== MVEL Language

*Available as of Camel version 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


The component supports 4 options, which are listed below.



[width="100%",cols="2,5,^1,2",options="header"]
|===
| Name | Description | Default | Type
| *camel.component.mvel.enabled* | Enable mvel component | true | Boolean
| *camel.component.mvel.resolve-property-placeholders* | Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. | true | Boolean
| *camel.language.mvel.enabled* | Enable mvel language | true | 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 link:message-filter.html[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

*Available as of 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>
-------------------------------------
