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Chapter 59. Kamelet

Both producer and consumer are supported

The Kamelet Component provides support for interacting with the Camel Route Template engine using Endpoint semantic.

59.1. Dependencies

When using kamelet with Red Hat build of Camel 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-kamelet-starter</artifactId>
</dependency>

59.2. URI format

kamelet:templateId/routeId[?options]

59.3. Configuring Options

Camel components are configured on two levels:

Component level
Endpoint level

59.3.1. Component Level Options

The component level is the highest level. The configurations you define at this level are inherited by all the endpoints. For example, a component can have security settings, credentials for authentication, urls for network connection, and so on.

Since components typically have pre-configured defaults for the most common cases, you may need to only configure a few component options, or maybe none at all.

You can configure components with Component DSL in a configuration file (application.properties|yaml), or directly with Java code.

59.3.2. Endpoint Level Options

At the Endpoint level you have many options, which you can use to configure what you want the endpoint to do. The options are categorized according to whether the endpoint is used as a consumer (from) or as a producer (to) or used for both.

You can configure endpoints directly in the endpoint URI as path and query parameters. You can also use Endpoint DSL and DataFormat DSL as type safe ways of configuring endpoints and data formats in Java.

When configuring options, use Property Placeholders for urls, port numbers, sensitive information, and other settings.

Placeholders allows you to externalize the configuration from your code, giving you more flexible and reusable code.

59.4. Component Options

The Kamelet component supports 9 options, which are listed below.

Name	Description	Default	Type
location (common)	The location(s) of the Kamelets on the file system. Multiple locations can be set separated by comma.	classpath:/kamelets	String
routeProperties (common)	Set route local parameters.		Map
templateProperties (common)	Set template local parameters.		Map
bridgeErrorHandler (consumer)	Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.	false	boolean
block (producer)	If sending a message to a kamelet endpoint which has no active consumer, then we can tell the producer to block and wait for the consumer to become active.	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
timeout (producer)	The timeout value to use if block is enabled.	30000	long
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
routeTemplateLoaderListener (advanced)	Autowired To plugin a custom listener for when the Kamelet component is loading Kamelets from external resources.		RouteTemplateLoaderListener

59.5. Endpoint Options

The Kamelet endpoint is configured using URI syntax:

kamelet:templateId/routeId

with the following path and query parameters:

59.5.1. Path Parameters (2 parameters)

Name	Description	Default	Type
templateId (common)	Required The Route Template ID.		String
routeId (common)	The Route ID. Default value notice: The ID will be auto-generated if not provided.		String

59.5.2. Query Parameters (8 parameters)

Name	Description	Default	Type
location (common)	Location of the Kamelet to use which can be specified as a resource from file system, classpath etc. The location cannot use wildcards, and must refer to a file including extension, for example file:/etc/foo-kamelet.xml.		String
bridgeErrorHandler (consumer)	Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.	false	boolean
exceptionHandler (consumer (advanced))	To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.		ExceptionHandler
exchangePattern (consumer (advanced))	Sets the exchange pattern when the consumer creates an exchange. Enum values: InOnly InOut InOptionalOut		ExchangePattern
block (producer)	If sending a message to a direct endpoint which has no active consumer, then we can tell the producer to block and wait for the consumer to become active.	true	boolean
failIfNoConsumers (producer)	Whether the producer should fail by throwing an exception, when sending to a kamelet endpoint with no active consumers.	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
timeout (producer)	The timeout value to use if block is enabled.	30000	long

Note

The kamelet endpoint is lenient, which means that the endpoint accepts additional parameters that are passed to the engine and consumed upon route materialization.

59.6. Discovery

If a Route Template is not found, the kamelet endpoint tries to load the related kamelet definition from the file system (by default classpath:/kamelets). The default resolution mechanism expect kamelet files to have the extension .kamelet.yaml.

59.7. Samples

Kamelets can be used as if they were standard Camel components. For example, suppose that we have created a Route Template as follows:

routeTemplate("setMyBody")
    .templateParameter("bodyValue")
    .from("kamelet:source")
        .setBody().constant("{{bodyValue}}");

Note

To let the Kamelet component wiring the materialized route to the caller processor, we need to be able to identify the input and output endpoint of the route and this is done by using kamele:source to mark the input endpoint and kamelet:sink for the output endpoint.

Then the template can be instantiated and invoked as shown below:

from("direct:setMyBody")
    .to("kamelet:setMyBody?bodyValue=myKamelet");

Behind the scenes, the Kamelet component does the following things:

It instantiates a route out of the Route Template identified by the given templateId path parameter (in this case setBody)
It will act like the direct component and connect the current route to the materialized one.

If you had to do it programmatically, it would have been something like:

routeTemplate("setMyBody")
    .templateParameter("bodyValue")
    .from("direct:{{foo}}")
        .setBody().constant("{{bodyValue}}");

TemplatedRouteBuilder.builder(context, "setMyBody")
    .parameter("foo", "bar")
    .parameter("bodyValue", "myKamelet")
    .add();

from("direct:template")
    .to("direct:bar");

59.8. Spring Boot Auto-Configuration

The component supports 10 options, which are listed below.

Name	Description	Default	Type
camel.component.kamelet.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.kamelet.block	If sending a message to a kamelet endpoint which has no active consumer, then we can tell the producer to block and wait for the consumer to become active.	true	Boolean
camel.component.kamelet.bridge-error-handler	Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.	false	Boolean
camel.component.kamelet.enabled	Whether to enable auto configuration of the kamelet component. This is enabled by default.		Boolean
camel.component.kamelet.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
camel.component.kamelet.location	The location(s) of the Kamelets on the file system. Multiple locations can be set separated by comma.	classpath:/kamelets	String
camel.component.kamelet.route-properties	Set route local parameters.		Map
camel.component.kamelet.route-template-loader-listener	To plugin a custom listener for when the Kamelet component is loading Kamelets from external resources. The option is a org.apache.camel.spi.RouteTemplateLoaderListener type.		RouteTemplateLoaderListener
camel.component.kamelet.template-properties	Set template local parameters.		Map
camel.component.kamelet.timeout	The timeout value to use if block is enabled.	30000	Long