Chunk

Since Camel 2.15

Only producer is supported

The Chunk component allows for processing a message using a Chunk template. This can be ideal when using Templating to generate responses for requests.

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&…​

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

At the component level, you set general and shared configurations that are, then, inherited by the endpoints. It is the highest configuration level.

For example, a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre-configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

You can configure components using:

  • the Component DSL.

  • in a configuration file (application.properties, *.yaml files, etc).

  • directly in the Java code.

Configuring Endpoint Options

You usually spend more time setting up endpoints because they have many options. These options help you customize what you want the endpoint to do. The options are also categorized into whether the endpoint is used as a consumer (from), as a producer (to), or both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL and DataFormat DSL as a type safe way of configuring endpoints and data formats in Java.

A good practice when configuring options is to use Property Placeholders.

Property placeholders provide a few benefits:

  • They help prevent using hardcoded urls, port numbers, sensitive information, and other settings.

  • They allow externalizing the configuration from the code.

  • They help the code to become more flexible and reusable.

The following two sections list all the options, firstly for the component followed by the endpoint.

Component Options

The Chunk 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 impose 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 allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

boolean

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

Endpoint Options

The Chunk endpoint is configured using URI syntax:

chunk:resourceUri

With the following path and query parameters:

Path Parameters (1 parameters)

Name Description Default Type

resourceUri (producer)

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

Query Parameters (9 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 impose 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 allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

boolean

contentCache (producer)

Sets whether to use resource content cache or not.

false

boolean

encoding (producer)

Define the encoding of the body.

String

extension (producer)

Define the file extension of the template.

String

themeFolder (producer)

Define the themes folder to scan.

String

themeLayer (producer)

Define the theme layer to elaborate.

String

themeSubfolder (producer)

Define the themes subfolder to scan.

String

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

Chunk component will look for a specific template in the 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.

Usage

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.

variables

The variables

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.

Message Headers

The Chunk component supports 2 message header(s), which is/are listed below:

Name Description Default Type

ChunkResourceUri (producer)

Constant: CHUNK_RESOURCE_URI

A URI for the template resource to use instead of the endpoint configured.

String

ChunkTemplate (producer)

Constant: CHUNK_TEMPLATE

The template to use instead of the endpoint configured.

String

Examples

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");

An example of Chunk component options use:

from("direct:in").
to("chunk:file_example?themeFolder=template&themeSubfolder=subfolder&extension=chunk");

In this example, the Chunk component will look for the file file_example.chunk in the folder template/subfolder.

The Email Example

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}

Spring Boot Auto-Configuration

When using chunk with Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

<dependency>
  <groupId>org.apache.camel.springboot</groupId>
  <artifactId>camel-chunk-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

The component supports 5 options, which are listed below.

Name Description Default Type

camel.component.chunk.allow-context-map-all

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 impose a potential security risk as this opens access to the full power of CamelContext API.

false

Boolean

camel.component.chunk.allow-template-from-header

Whether to allow to use resource template from header or not (default false). Enabling this allows to specify dynamic templates via message header. However this can be seen as a potential security vulnerability if the header is coming from a malicious user, so use this with care.

false

Boolean

camel.component.chunk.autowired-enabled

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

Boolean

camel.component.chunk.enabled

Whether to enable auto configuration of the chunk component. This is enabled by default.

Boolean

camel.component.chunk.lazy-start-producer

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

Boolean
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