Chapter 234. MVEL Component Available as of Camel version 2.12 The mvel: component allows you to process a message using an 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: <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> 234.1. URI format 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&... 234.2. Options The MVEL component supports 2 options, which are listed below. Name Description Default Type allowContextMapAll (producer) 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 imposes a potential security risk as this opens access to the full power of CamelContext API. false boolean allowTemplateFromHeader (producer) Whether to allow to use resource template from header or not (default false). Enabling this option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. false boolean The MVEL endpoint is configured using URI syntax: with the following path and query parameters: 234.2.1. Path Parameters (1 parameters): 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 234.2.2. Query Parameters (5 parameters): Name Description Default Type allowContextMapAll (producer) 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 imposes a potential security risk as this opens access to the full power of CamelContext API. false boolean allowTemplateFromHeader (producer) Whether to allow to use resource template from header or not (default false). Enabling this option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. false boolean contentCache (producer) Sets whether to use resource content cache or not false boolean encoding (producer) Character encoding of the resource content. String synchronous (advanced) Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). false boolean 234.3. Spring Boot Auto-Configuration The component supports 4 options, which are listed below. 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 234.4. Message Headers The mvel component sets a couple headers on the message. Header Description CamelMvelResourceUri The templateName as a String object. 234.5. MVEL Context Camel will provide exchange information in the MVEL context (just a Map ). The Exchange is transfered as: 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). 234.6. 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. 234.7. 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. 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. 234.8. Samples For example you could use something like 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: from("direct:in"). setHeader("CamelMvelResourceUri").constant("path/to/my/template.mvel"). to("mvel:dummy?allowTemplateFromHeader=true"); To specify a template directly as a header the component should use dynamically via a header, so for example: from("direct:in"). setHeader("CamelMvelTemplate").constant("@{\"The result is \" + request.body * 3}\" }"). to("velocity:dummy?allowTemplateFromHeader=true"); Warning Enabling the allowTemplateFromHeader option has security ramifications. For example, if the header contains untrusted or user derived content, this can ultimately impact on the confidentility and integrity of your end application, so use this option with caution. 234.9. See Also Configuring Camel Component Endpoint Getting Started

Commands:
<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>
mvel:templateName[?options]
mvel:resourceUri
from("activemq:My.Queue"). to("mvel:com/acme/MyResponse.mvel");
from("direct:in"). setHeader("CamelMvelResourceUri").constant("path/to/my/template.mvel"). to("mvel:dummy?allowTemplateFromHeader=true");
from("direct:in"). setHeader("CamelMvelTemplate").constant("@{\"The result is \" + request.body * 3}\" }"). to("velocity:dummy?allowTemplateFromHeader=true");