Java Implementation Model for Event Processing (TUSCANY) edited by Mike Edwards
Page:
http://cwiki.apache.org/confluence/display/TUSCANY/Java+Implementation+Model+for+Event+Processing
Changes:
http://cwiki.apache.org/confluence/pages/diffpagesbyversion.action?pageId=99635&originalVersion=10&revisedVersion=11
Content:
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This page describes the Java Implementation for Event Processing.
The Java Implementation for Event Processing is an extension of the standard
SCA Java Implementation model. All the standard SCA Java implementation
features continue to be available to Java implementations. The following
features are added:
* Ability to define one or more methods of the implementation class to be
*{_}consumer methods{_}*, consuming one or more *{_}event types{_}*
* Ability to define a field or setter method of the implementation class as an
event *{_}producer{_}*, with one or more business methods producing one or more
*{_}event types _*
* Ability to define *{_}event types{_}* as Java POJO classes
h2. Event Types
Event types are defined through Java classes which are annotated with a
@EventType annotation. The @EventType annotation has a single parameter
which is the *{_}name{_}* of the event type.
{code}
@EventType(ExampleEvent)
public class ExampleEvent {
public String eventData;
} // end class ExampleEvent
{code}
The name may be:
* *{_}unqualified{_}*, in which case the EventType name is qualified by the
package name of the class itself
* *{_}qualified{_}*, in which case the EventType name is used as it is declared
Note that the Event Type name maps to an XSD QName using the Java-to-WSDL
mapping as defined by JAX-WS.
The Event type(s) handled by a consumer method or a producer method is defined
in one of two ways:
# The method has a parameter that is of a class annotated with the @EventType
annotation (of a single event type)
# The method is itself annotated with the @EventTypes annotation for one or
more event types - where the method parameter is of some generic type such as
java.lang.Object which does not specify an EventType
h2. Event Consumer methods
Each method of the implementation that is a consumer for events is annotated
with a @Consumer annotation. Each method must have a *{_}void{_}* return
type and a single parameter that is either a specific event type or a
superclass of one or more event types, including java.lang.Object, which is
treated as the supertype of all event types.
{code}
public class ConsumerrExample {
private ExampleProducer eventProducer;
@Consumer(ExampleConsumer)
public void someBusinessMethod( ExampleEvent theEvent ) {
String businessData = theEvent.eventData;
// do business processing...
} // end method someBusinessMethod
} // end class
{code}
h2. Event Producers
Event Producers are identified as a Field or a Setter method annotated with a
@Producer annotation
It is required that the Field or Setter method is typed by a Java
interface. The Java interface must have one or more methods, each of
which has a *{_}void{_}* return type and a single parameter that is either a
specific event type or a superclass of one or more event types, including
java.lang.Object, which is treated as the supertype of all event types.
{code}
@Remotable
public interface ExampleProducer {
void produceExampleEvent( ExampleEvent theEvent);
} // end interface ExampleProducer
@EventType(ExampleEvent)
public class ExampleEvent {
public String eventData;
} // end class ExampleEvent
public class ProducerExample {
private ExampleProducer eventProducer;
@Producer(ExampleEvent)
public void setEventProducer( ExampleProducer theProducer ) {
eventProducer = theProducer;
return;
} // end method setEventProducer
public void someBusinessMethod() {
theEvent = new ExampleEvent();
theEvent.eventData = "Some Data";
eventProducer.produceExampleEvent( theEvent );
} // end method someBusinessMethod
} // end class
{code}
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