Writing Custom Annotations

Writing custom annotations that integrate in the framework is also very easy. Follow these steps:

Create you annotation using the following template. All annotations are expected to be annotated with the
@Accepts and @Implementation annotations, and all annotations are expected to have the message(), errorCode() and messageKey() attributes.

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import com.planetalia.dynject.metamodel.Accepts;
import com.planetalia.dynject.metamodel.Implementation;

@Target(value={ElementType.FIELD,ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Accepts({place here the list of classes you will accept })
@Implementation(Class that implements your annotation)
public @interface MyAnnotation {

Include your custom annotation attributes

/**
* Literal message to use if validation fails.
* @return Literal message to use if validation fails.
*/
String message() default "";
/**
* Error code to use if validation fails.
* @return Error code to use if validation fails.
*/
String errorCode() default "";
/**
* Message key to use if validation fails. Default is {@link Messages#REQUIRED_FIELD}
* @return Message key to use if validation fails.
*/
String messageKey() default Messages.REQUIRED_FIELD;
}

Write the class that implements the annotation behaviour. This class should implement the IDataHandler interface, although it's easier to subclass DataHandlerSupport, which provides several useful utility methods. Your implementing class should be thread-safe and reentrant.
Your annotation can get any runtime operation parameters from the env parameter. In particular, you should use the env.getLocale() method to retrieve the Locale under which the user wants your annotation to operate in a particular invocation. This locale may change from invocation to invocation, and needs not necessarily be the default locale (Think, for example, of your annotation processing data coming from an HTTP Request : each request will have its own locale).

A useful starting point would be to look at the source code of some of the existing annotations. Generally speaking in Dynject annotation @X is implemented in XImpl ( @Required in RequiredImpl, @MinInclusive in MinInclusiveImpl and so forth)