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

*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

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</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.allow-context-map-all* | Sets whether the context map should allow access to all details. By default only the message body and headers can be accessed. This option can be enabled for full access to the current Exchange and CamelContext. Doing so impose a potential security risk as this opens access to the full power of CamelContext API. | false | Boolean
| *camel.component.mvel.allow-template-from-header* | Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care. | false | Boolean
| *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 xref:latest@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

*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>
-------------------------------------
