Cron

Since Camel 3.1

Only consumer is supported

The Cron component is a generic interface component that allows triggering events at specific time interval specified using the Unix cron syntax (e.g. 0/2 * * * * ? to trigger an event every two seconds).

Being an interface component, the Cron component does not contain a default implementation, instead it requires that the users plug the implementation of their choice.

The following standard Camel components support the Cron endpoints:

  • Camel-quartz

  • Camel-spring

The Cron component is also supported in Camel K, which can use the Kubernetes scheduler to trigger the routes when required by the cron expression. Camel K does not require additional libraries to be plugged when using cron expressions compatible with Kubernetes cron syntax.

Maven users will need to add the following dependency to their pom.xml for this component:

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

Additional libraries may be needed in order to plug a specific implementation.

Options

The Cron component supports 3 options, which are listed below.

Name Description Default Type

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

basicPropertyBinding (advanced)

Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

boolean

cronService (advanced)

The id of the CamelCronService to use when multiple implementations are provided

String

The Cron endpoint is configured using URI syntax:

cron:name

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

name

Required The name of the cron trigger

String

Query Parameters (6 parameters):

Name Description Default Type

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

schedule (consumer)

Required A cron expression that will be used to generate events

String

exceptionHandler (consumer)

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)

Sets the exchange pattern when the consumer creates an exchange. The value can be one of: InOnly, InOut, InOptionalOut

ExchangePattern

basicPropertyBinding (advanced)

Whether the endpoint should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

boolean

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

Usage

The component can be used to trigger events at specified times, as in the following example:

from("cron:tab?schedule=0/1+*+*+*+*+?")
.setBody().constant("event")
.log("${body}");

The schedule expression 0/3+10+++*+? can be also written as 0/3 10 * * * ? and triggers an event every three seconds only in the tenth minute of each hour.

Parts in the schedule expression means (in order):

  • Seconds (optional)

  • Minutes

  • Hours

  • Day of month

  • Month

  • Day of week

  • Year (optional)

Schedule expressions can be made of 5 to 7 parts. When expressions are composed of 6 parts, the first items is the "seconds" part (and year is considered missing).

Other valid examples of schedule expressions are:

  • 0/2 * * * ? (5 parts, an event every two minutes)

  • 0 0/2 * * * MON-FRI 2030 (7 parts, an event every two minutes only in year 2030)

Routes can also be written using the XML DSL.

<route>
    <from uri="cron:tab?schedule=0/1+*+*+*+*+?"/>
    <setBody>
      <constant>event</constant>
    </setBody>
    <to uri="log:info"/>
</route>

Spring Boot Auto-Configuration

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

The component supports 4 options, which are listed below.

Name Description Default Type

camel.component.cron.basic-property-binding

Whether the component should use basic property binding (Camel 2.x) or the newer property binding with additional capabilities

false

Boolean

camel.component.cron.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.cron.cron-service

The id of the CamelCronService to use when multiple implementations are provided

String

camel.component.cron.enabled

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

Boolean