Camel Components

Mustache

Since Camel 2.12

Only producer is supported

The Mustache component allows for processing a message using a Mustache 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-mustache</artifactId>
<version>x.x.x</version> <!-- use the same version as your Camel core version -->
</dependency>

URI format

mustache:templateName[?options]

Where templateName is the classpath-local URI of the template to invoke; or the complete URL of the remote template (e.g.: file://folder/myfile.mustache).

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 Mustache component supports the following 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

contentCache (producer)

Sets whether to use resource content cache or not.

true

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

mustacheFactory (advanced)

Autowired To use a custom MustacheFactory.

MustacheFactory

Endpoint Options

The Mustache endpoint is configured using URI syntax:

mustache:resourceUri

With the following path and query parameters:

Path 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

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.

true

boolean

encoding (producer)

Character encoding of the resource content.

String

endDelimiter (producer)

Characters used to mark template code end.

}}

String

startDelimiter (producer)

Characters used to mark template code beginning.

{{

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

Message Headers

The Mustache component supports the following message header(s), which is/are listed below:

Name Description Default Type

CamelMustacheResourceUri (producer)

Constant: MUSTACHE_RESOURCE_URI

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

String

CamelMustacheTemplate (producer)

Constant: MUSTACHE_TEMPLATE

The template to use instead of the endpoint configured.

String

Message Body

The message body at each side of the Mustache component: Consumer is the body of the messages the consumer creates, Consumer reply the bodies a consumer that answers its caller can reply with, Producer input the bodies the producer can send or write, and Producer output the body after the producer.

Side Body Description

Producer input

any

The template gets the body as body, as it is: text, or a Map, a List or a POJO to read from; convert bytes or a stream to a String first. The template is the resource, or the CamelMustacheTemplate or CamelMustacheResourceUri header with allowTemplateFromHeader=true, and never the body.

Producer output

text (java.lang.String)

The text the template writes, also when it is JSON: unmarshal it to read its fields. Values in double braces are HTML-escaped, in triple braces as they are. The headers are kept.

The bodies are the ones with the default options. A side that is not listed is not known, and tooling does not guess it. The carriers, the sides and the tools that use them are described in Message Body Types.

Usage

Mustache Context

Camel will provide exchange information in the Mustache context (just a Map). The Exchange is transferred as: The body, header, headers, variable, variables and exception entries are always there; the others only when the endpoint has allowContextMapAll=true.

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, and the endpoint has allowTemplateFromHeader=true, then Camel uses this over the endpoint configured resource. This allows you to provide a dynamic template at runtime.

Content cache

By default (contentCache=true) the endpoint reads and compiles its template once and uses it for every exchange. With contentCache=false the template is read and compiled again for each exchange, so a template that changes while the route runs (such as a file) is picked up by the next exchange.

Examples

For example, you could use something like:

  • Java

  • XML

  • YAML

from("activemq:My.Queue")
    .to("mustache:com/acme/MyResponse.mustache");
<route>
  <from uri="activemq:My.Queue"/>
  <to uri="mustache:com/acme/MyResponse.mustache"/>
</route>
- route:
    from:
      uri: activemq:My.Queue
      steps:
        - to:
            uri: mustache:com/acme/MyResponse.mustache

To use a Mustache 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:

  • Java

  • XML

  • YAML

from("activemq:My.Queue")
    .to("mustache:com/acme/MyResponse.mustache")
    .to("activemq:Another.Queue");
<route>
  <from uri="activemq:My.Queue"/>
  <to uri="mustache:com/acme/MyResponse.mustache"/>
  <to uri="activemq:Another.Queue"/>
</route>
- route:
    from:
      uri: activemq:My.Queue
      steps:
        - to:
            uri: mustache:com/acme/MyResponse.mustache
        - to:
            uri: activemq:Another.Queue

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

  • Java

  • XML

  • YAML

from("direct:in")
    .setHeader("CamelMustacheResourceUri").constant("path/to/my/template.mustache")
    .to("mustache:dummy?allowTemplateFromHeader=true");
<route>
  <from uri="direct:in"/>
  <setHeader name="CamelMustacheResourceUri">
    <constant>path/to/my/template.mustache</constant>
  </setHeader>
  <to uri="mustache:dummy?allowTemplateFromHeader=true"/>
</route>
- route:
    from:
      uri: direct:in
      steps:
        - setHeader:
            name: CamelMustacheResourceUri
            expression:
              constant:
                expression: path/to/my/template.mustache
        - to:
            uri: mustache:dummy
            parameters:
              allowTemplateFromHeader: true

The Email Example

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

Dear {{headers.lastName}}, {{headers.firstName}}

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

Regards Camel Riders Bookstore
{{body}}