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Writing Custom Modules

Adding special annotations to a standard Java class will expose it as a Mule extension, making it possible to use it within Mule ESB. These annotations will be processed by the DevKit’s annotations processing tool that will generate all the necessary Mule specific code. The DevKit provides a special class level annotation that tells the Annotation Processor to export the POJO functionality as a Mule Module.

The @Module annotation

The class level annotation @Module indicates that a Java class needs to be processed by the DevKit Annotation Processing Tool and considered as a Mule Module.

The @Module annotation defines the following annotation type element declarations:

Annotation type element Description Required/Optional Default value

name

defines the name of this Mule Module

REQUIRED

 

schemaVersion

the version of the schema that will be generated by the DevKit

OPTIONAL

1.0

namespace

the namespace of this Mule Module 

OPTIONAL

http://www.mulesoft.org/schema/mule/name

schemaLocation

the location of the schema file that will be written to the spring.schemas file

OPTIONAL

http://www.mulesoft.org/schema/mule/name/schemaVersion/mule-name.xsd 

and

http://www.mulesoft.org/schema/mule/name/current/mule-name.xsd

minMuleVersion

the minimum Mule version for which this Mule Module is to be used. This will be checked in runtime during the initialise phase of the lifecycle.

OPTIONAL

3.2

poolable

whether this module is poolable

OPTIONAL.

false

Mule version verification

The minMuleVersion annotation parameter value is compared at runtime against the version of Mule where it is deployed. This check is done during the Initialisation phase and in case the version of the Mule instance is older than minMuleVersion the extension will fail to initialise and a proper error message will be logged.

The goal of this verification is to prevent possible runtime errors when the extension is executed in an older Mule version than the one the extension was originally developed for.

Restrictions

Some restrictions apply to types annotated with @Module:

  • Cannot be applied to interfaces

  • Cannot be applied to final classes

  • Cannot be applied to parametrized classes

  • Cannot be applied to non-public classes