THIS IS A TEST INSTANCE. ALL YOUR CHANGES WILL BE LOST!!!!
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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.
URI format
Maven users will need to add the following dependency to their pom.xml for this component:
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URI format
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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
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You can append query options to the URI in the following format, ?option=value&option=value&...
Options
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Option | Default | Description |
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| Velocity based file loader cache. |
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false
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Cache for the resource content when |
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it is loaded. |
Headers
Camel will store a reference to the resource in the message header in the key org.apache.camel.velocity.resource. The Resource is an org.springframework.core.io.Resource object.
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Note : as of Camel 2.9 cached resource content can be cleared via JMX using the endpoint's | ||
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| Character encoding of the resource content. |
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| New option in Camel 2.1: The URI of the properties file which is used for VelocityEngine initialization. |
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):
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Header | Description |
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| The templateName as a |
| Camel 2.16: To add additional information to the used VelocityContext. The value of this header should be a |
Headers set during the Velocity evaluation are In Camel 1.4 headers set during the velocity evaluation is returned to the message and added as headers. Then its kinda possible to return values from Velocity to the Message. See this unit test TODO.
For example, to set the header value of fruit in the Velocity template .tm:
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The fruit header is now accessible from the message.out.headers.
Velocity Context
Camel will provide exchange information in the Velocity context (just a Map). The Exchange is transfered as:
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key | value |
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| The |
| The |
| The headers of the |
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In message. | |
| The Camel Context instance. |
| The |
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In message. | |
| The |
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In message. | |
| The |
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In message body. | |
| The |
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Out message (only for InOut message exchange pattern). | |
| The |
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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
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Hot reloading
The velocity Velocity template resource is, by default, hot reloadable for both file and classpath resources (expanded jar). Setting the If you set contentCache=true then , Camel will only load the resource once, and thus hot reloading is not possible. This scenario can be used in production usage , when the resource never changes.
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.
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Header | Type | Description |
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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. |
Samples
For example you could use something like
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To use a velocity Velocity template to formulate a response for 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
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the following route:
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And to use the content cache, ege.g. for use in production usage , where the .vm template never changes:
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And a file based resource:
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In Camel 2.1 it's possible to specify what template the component should use dynamically via a header, so for example:
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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:
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The Email Sample
In this sample we want to use Velocity as templating for an order confirmation email. The email template is laid out in Velocity as:
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And the java code:
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