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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}