| [[mvel-component]] |
| = MVEL Component |
| :page-source: components/camel-mvel/src/main/docs/mvel-component.adoc |
| |
| *Available as of Camel version 2.12* |
| |
| The MVEL component allows you to process a message using an |
| http://mvel.codehaus.org/[MVEL] template. This can be ideal when using |
| Templating to generate responses for requests. |
| |
| Maven users will need to add the following dependency to their `pom.xml` |
| for this component: |
| |
| [source,xml] |
| ------------------------------------------------------------ |
| <dependency> |
| <groupId>org.apache.camel</groupId> |
| <artifactId>camel-mvel</artifactId> |
| <version>x.x.x</version> |
| <!-- use the same version as your Camel core version --> |
| </dependency> |
| ------------------------------------------------------------ |
| |
| == URI format |
| |
| [source,java] |
| --------------------------- |
| mvel:templateName[?options] |
| --------------------------- |
| |
| Where *templateName* is the classpath-local URI of the template to |
| invoke; or the complete URL of the remote template (eg: |
| \file://folder/myfile.mvel). |
| |
| You can append query options to the URI in the following format, |
| `?option=value&option=value&...` |
| |
| == Options |
| |
| |
| // component options: START |
| The MVEL component supports 1 options, which are listed below. |
| |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | Name | Description | Default | Type |
| | *basicPropertyBinding* (advanced) | Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | boolean |
| |=== |
| // component options: END |
| |
| |
| |
| |
| // endpoint options: START |
| The MVEL endpoint is configured using URI syntax: |
| |
| ---- |
| mvel:resourceUri |
| ---- |
| |
| with the following path and query parameters: |
| |
| === Path Parameters (1 parameters): |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | Name | Description | Default | Type |
| | *resourceUri* | *Required* Path to the resource. You can prefix with: classpath, file, http, ref, or bean. classpath, file and http loads the resource using these protocols (classpath is default). ref will lookup the resource in the registry. bean will call a method on a bean to be used as the resource. For bean you can specify the method name after dot, eg bean:myBean.myMethod. | | String |
| |=== |
| |
| |
| === Query Parameters (5 parameters): |
| |
| |
| [width="100%",cols="2,5,^1,2",options="header"] |
| |=== |
| | Name | Description | Default | Type |
| | *contentCache* (producer) | Sets whether to use resource content cache or not | false | boolean |
| | *encoding* (producer) | Character encoding of the resource content. | | String |
| | *lazyStartProducer* (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 |
| | *basicPropertyBinding* (advanced) | Whether the endpoint should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities | false | boolean |
| | *synchronous* (advanced) | Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). | false | boolean |
| |=== |
| // endpoint 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 4 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.enabled* | Enable mvel component | 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 |
| |
| |
| |
| |
| == Message Headers |
| |
| The mvel component sets a couple headers on the message. |
| |
| [width="100%",cols="10%,90%",options="header",] |
| |======================================================================= |
| |Header |Description |
| |
| |`CamelMvelResourceUri` |The *templateName* as a `String` object. |
| |======================================================================= |
| |
| == MVEL Context |
| |
| Camel will provide exchange information in the MVEL context (just a |
| `Map`). The `Exchange` is transfered as: |
| |
| [width="100%",cols="10%,90%",options="header",] |
| |======================================================================= |
| |key |value |
| |
| |`exchange` |The `Exchange` itself. |
| |
| |`exchange.properties` |The `Exchange` properties. |
| |
| |`headers` |The headers of the In message. |
| |
| |`camelContext` |The Camel Context intance. |
| |
| |`request` |The In message. |
| |
| |`in` |The In message. |
| |
| |`body` |The In message body. |
| |
| |`out` |The Out message (only for InOut message exchange pattern). |
| |
| |`response` |The Out message (only for InOut message exchange pattern). |
| |======================================================================= |
| |
| == Hot reloading |
| |
| The mvel template resource is, by default, hot reloadable for both file |
| and classpath resources (expanded jar). If you set `contentCache=true`, |
| Camel will only load the resource once, and thus hot reloading is not |
| possible. This scenario can be used in production, when the resource |
| never changes. |
| |
| == Dynamic templates |
| |
| Camel provides two headers by which you can define a different resource |
| location for a template or the template content itself. If any of these |
| headers is set then Camel uses this over the endpoint configured |
| resource. This allows you to provide a dynamic template at runtime. |
| |
| [width="100%",cols="10%,10%,80%",options="header",] |
| |======================================================================= |
| |Header |Type |Description |
| |
| |CamelMvelResourceUri |String |A URI for the template resource to use instead of the endpoint |
| configured. |
| |
| |CamelMvelTemplate |String |The template to use instead of the endpoint configured. |
| |======================================================================= |
| |
| == Samples |
| |
| For example you could use something like |
| |
| [source,java] |
| -------------------------------------- |
| from("activemq:My.Queue"). |
| to("mvel:com/acme/MyResponse.mvel"); |
| -------------------------------------- |
| |
| To use a MVEL template to formulate a response to a message for InOut |
| message exchanges (where there is a `JMSReplyTo` header). |
| |
| To specify what template the component should use dynamically via a |
| header, so for example: |
| |
| [source,java] |
| ------------------------------------------------------------------------- |
| from("direct:in"). |
| setHeader("CamelMvelResourceUri").constant("path/to/my/template.mvel"). |
| to("mvel:dummy"); |
| ------------------------------------------------------------------------- |
| |
| To specify a template directly as a header the component should use |
| dynamically via a header, so for example: |
| |
| [source,java] |
| ------------------------------------------------------------------------------------------ |
| from("direct:in"). |
| setHeader("CamelMvelTemplate").constant("@{\"The result is \" + request.body * 3}\" }"). |
| to("velocity:dummy"); |
| ------------------------------------------------------------------------------------------ |
| |