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Scalate Camel Component

Scalate Camel Component

The scalate: camel component allows you to process a message using Scalate template, which supports various template languages such as

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, and use the correct version of Scalate:

<dependency>
    <groupId>org.fusesource.scalate</groupId>
    <artifactId>scalate-camel_${scala_compat_tag}</artifactId>
    <version>${scalate.version}</version>
</dependency>

URI format

scalate: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.ssp).

You can append query options to the URI in the following format, ?option=value&option=value&...

Message Headers

The scalate component sets a couple headers on the message (you can't set these yourself and from Camel 2.1 scalate component will not set these headers which will cause some side effect on the dynamic template support):

Header Description
CamelScalateResource The resource as an org.springframework.core.io.Resource object.
CamelScalateResourceUri The templateName as a String object.

Headers set during the Scalate evaluation are returned to the message and added as headers. Then its kinda possible to return values from Scalate to the Message.

For example, to set the header value of fruit in the Scalate template .tm:

<% in.setHeader('fruit', 'Apple') %>

The fruit header is now accessible from the message.out.headers.

Scalate Context

Camel will provide exchange information in the Scalate context (just a Map). The Exchange is transfered as:

key value
exchange The Exchange itself.
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 Scalate template resource is, by default, hot reloadable for both file and classpath resources (expanded jar).

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
CamelScalateResourceUri String An URI for the template resource to use instead of the endpoint configured.
CamelScalateTemplate String The template to use instead of the endpoint configured.

Samples

For example you could use something like

from("activemq:My.Queue").
  to("scalate:com/acme/MyResponse.ssp");

To use a Scalate 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("scalate:com/acme/MyResponse.scaml").
  to("activemq:Another.Queue");

It's possible to specify what template the component should use dynamically via a header, so for example:

from("direct:in").
  setHeader("CamelScalateResourceUri").
    constant("path/to/my/template.scaml").
  to("scalate:dummy");

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("CamelScalateTemplate").
    constant("<%@ attribute body: Object %>\n" + 
      "Hi this is a scalate template that can do templating ${body}").
  to("scalate:dummy");

The Email Sample

In this sample we want to use Scalate templating for an order confirmation email. The email template is laid out in Scalate as:

<%@ attribute in: org.apache.camel.scala.RichMessage %>

Dear ${in("firstName")}

Thanks for the order of ${in("item")}.

Regards Camel Riders Bookstore
${in.body}