Kamelet

Since Camel 3.8

Both producer and consumer are supported

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

URI format

kamelet:templateId/routeId[?options]

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. 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.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

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

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

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

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.

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.

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

Endpoint Options

The Kamelet endpoint is configured using URI syntax:

kamelet:templateId/routeId

with the following path and query parameters:

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

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.

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.

boolean

timeout (producer)

The timeout value to use if block is enabled.

30000

long

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

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.

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}}");

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:

  1. it instantiates a route out of the Route Template identified by the given templateId path parameter (in this case setBody)

  2. 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");

Spring Boot Auto-Configuration

When using kamelet 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-kamelet-starter</artifactId>
  <version>x.x.x</version>
  <!-- use the same version as your Camel core version -->
</dependency>

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
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