Red Hat Training

A Red Hat training course is available for Red Hat Fuse

Chapter 21. Chunk

Chunk Component

Available as of Camel 2.15
The chunk: component allows for processing a message using a Chunk 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-chunk</artifactId>
<version>x.x.x</version> <!-- use the same version as your Camel core version -->
</dependency>

URI format

chunk:templateName[?options]
Where templateName is the classpath-local URI of the template to invoke.
You can append query options to the URI in the following format, ?option=value&option=value&...

Options

Option
Default
Description
allowContextMapAll (producer)
false
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.
allowTemplateFromHeader (producer)
false
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.
encoding
null
Character encoding of the resource content.
themesFolder
null
Alternative folder to scan for a template name.
themeSubfolder
null
Alternative subfolder to scan for a template name if themeFolder parameter is set.
themeLayer
null
A specific layer of a template file to use as template.
extension
null
Alternative extension to scan for a template name if themeFolder and themeSubfolder are set.
Chunk component will look for a specific template in themes folder with extensions .chtml or .cxml. If you need to specify a different folder or extensions, you will need to use the specific options listed above.

Chunk Context

Camel will provide exchange information in the Chunk context (just a Map). The Exchange is transferred as:
key
value
exchange
The Exchange itself.
exchange.properties
The Exchange properties.
headers
The headers of the In message.
camelContext
The Camel Context.
request
The In message.
body
The In message body.
response
The Out message (only for InOut message exchange pattern).

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
Support Version
ChunkConstants.CHUNK_RESOURCE_URI
String
A URI for the template resource to use instead of the endpoint configured.
ChunkConstants.CHUNK_TEMPLATE
String
The template to use instead of the endpoint configured.

Samples

For example you could use something like: 
from("activemq:My.Queue").
to("chunk:template");
To use a Chunk template to formulate a response for 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: 
from("activemq:My.Queue").
to("chunk:template").
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(ChunkConstants.CHUNK_RESOURCE_URI).constant("template").
to("chunk: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.
An example of Chunk component options use: 
from("direct:in").
to("chunk:file_example?themeFolder=template&themeSubfolder=subfolder&extension=chunk");
In this example Chunk component will look for the file file_example.chunk in the folder template/subfolder.

The Email Sample

In this sample we want to use Chunk templating for an order confirmation email. The email template is laid out in Chunk as: 
Dear {$headers.lastName}, {$headers.firstName}

Thanks for the order of {$headers.item}.

Regards Camel Riders Bookstore
{$body}