MVEL

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:

"request.body.familyName"
   // or
"getRequest().getBody().getFamilyName()"

Mvel Options

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

Name Default Java Type Description

trim

true

Boolean

Whether to trim the value to remove leading and trailing whitespaces and line breaks

Variables

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 Message Filter in XML

<route>
  <from uri="seda:foo"/>
  <filter>
    <mvel>request.headers.foo == 'bar'</mvel>
    <to uri="seda:bar"/>
  </filter>
</route>

And the sample using Java DSL:

   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:

.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).

<dependency>
  <groupId>org.apache.camel</groupId>
  <artifactId>camel-mvel</artifactId>
  <version>x.x.x</version>
</dependency>

Spring Boot Auto-Configuration

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

<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 7 options, which are listed below.

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.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.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