Chapter 363. Velocity Component Available as of Camel version 1.2 The velocity: component allows you to process a message using an Apache Velocity 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-velocity</artifactId> <version>x.x.x</version> <!-- use the same version as your Camel core version --> </dependency> 363.1. URI format velocity: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.vm ). You can append query options to the URI in the following format, ?option=value&option=value&... 363.2. Options The Velocity component supports 4 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 resolveProperty Placeholders (advanced) Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders. true boolean velocityEngine (advanced) To use the VelocityEngine otherwise a new engine is created VelocityEngine The Velocity endpoint is configured using URI syntax: with the following path and query parameters: 363.2.1. 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 363.2.2. Query Parameters (7 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 loaderCache (producer) Enables / disables the velocity resource loader cache which is enabled by default true boolean propertiesFile (producer) The URI of the properties file which is used for VelocityEngine initialization. String synchronous (advanced) Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported). false boolean 363.3. Spring Boot Auto-Configuration The component supports 3 options, which are listed below. Name Description Default Type camel.component.velocity.enabled Enable velocity component true Boolean camel.component.velocity.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.component.velocity.velocity-engine To use the VelocityEngine otherwise a new engine is created. The option is a org.apache.velocity.app.VelocityEngine type. String 363.4. Message Headers The velocity component sets a couple headers on the message (you can't set these yourself and from Camel 2.1 velocity component will not set these headers which will cause some side effect on the dynamic template support): Header Description CamelVelocityResourceUri The templateName as a String object. CamelVelocitySupplementalContext Camel 2.16: To add additional information to the used VelocityContext. The value of this header should be a Map with key/values that will added (override any existing key with the same name). This can be used to pre setup some common key/values you want to reuse in your velocity endpoints. Headers set during the Velocity evaluation are returned to the message and added as headers. Then its kinda possible to return values from Velocity to the Message. For example, to set the header value of fruit in the Velocity template .tm : USDin.setHeader("fruit", "Apple") The fruit header is now accessible from the message.out.headers . 363.5. Velocity Context Camel will provide exchange information in the Velocity 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 instance. 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). Since Camel-2.14, you can setup a custom Velocity Context yourself by setting the message header *CamelVelocityContext *just like this VelocityContext velocityContext = new VelocityContext(variableMap); exchange.getIn().setHeader("CamelVelocityContext", velocityContext); 363.6. Hot reloading The Velocity 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. 363.7. Dynamic templates Available as of Camel 2.1 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 CamelVelocityResourceUri String Camel 2.1: A URI for the template resource to use instead of the endpoint configured. CamelVelocityTemplate String Camel 2.1: The template to use instead of the endpoint configured. 363.8. Samples For example you could use something like from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm"); To use a Velocity template to formulate a response to a message for InOut message exchanges (where there is a JMSReplyTo header). If you want to use InOnly and consume the message and send it to another destination, you could use the following route: from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm"). to("activemq:Another.Queue"); And to use the content cache, e.g. for use in production, where the .vm template never changes: from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm?contentCache=true"). to("activemq:Another.Queue"); And a file based resource: from("activemq:My.Queue"). to("velocity:file://myfolder/MyResponse.vm?contentCache=true"). to("activemq:Another.Queue"); In Camel 2.1 it's possible to specify what template the component should use dynamically via a header, so for example: from("direct:in"). setHeader("CamelVelocityResourceUri").constant("path/to/my/template.vm"). to("velocity:dummy?allowTemplateFromHeader=true"); In Camel 2.1 it's possible to specify a template directly as a header the component should use dynamically via a header, so for example: from("direct:in"). setHeader("CamelVelocityTemplate").constant("Hi this is a velocity template that can do templating USD{body}"). 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. 363.9. The Email Sample In this sample we want to use Velocity templating for an order confirmation email. The email template is laid out in Velocity as: Dear USD{headers.lastName}, USD{headers.firstName} Thanks for the order of USD{headers.item}. Regards Camel Riders Bookstore USD{body} And the java code: 363.10. See Also Configuring Camel Component Endpoint Getting Started

Commands:
<dependency> <groupId>org.apache.camel</groupId> <artifactId>camel-velocity</artifactId> <version>x.x.x</version> <!-- use the same version as your Camel core version --> </dependency>
velocity:templateName[?options]
velocity:resourceUri
USDin.setHeader("fruit", "Apple")
VelocityContext velocityContext = new VelocityContext(variableMap); exchange.getIn().setHeader("CamelVelocityContext", velocityContext);
from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm");
from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm"). to("activemq:Another.Queue");
from("activemq:My.Queue"). to("velocity:com/acme/MyResponse.vm?contentCache=true"). to("activemq:Another.Queue");
from("activemq:My.Queue"). to("velocity:file://myfolder/MyResponse.vm?contentCache=true"). to("activemq:Another.Queue");
from("direct:in"). setHeader("CamelVelocityResourceUri").constant("path/to/my/template.vm"). to("velocity:dummy?allowTemplateFromHeader=true");
from("direct:in"). setHeader("CamelVelocityTemplate").constant("Hi this is a velocity template that can do templating USD{body}"). to("velocity:dummy?allowTemplateFromHeader=true");
Dear USD{headers.lastName}, USD{headers.firstName} Thanks for the order of USD{headers.item}. Regards Camel Riders Bookstore USD{body}