# DomainEventCreationConcern.java

    /**
     *
     * Copyright 2009-2010 Rickard Öberg AB
     *
     * Licensed under the Apache License, Version 2.0 (the "License");
     * you may not use this file except in compliance with the License.
     * You may obtain a copy of the License at
     *
     *     http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */

    package org.qi4j.library.eventsourcing.domain.factory;

    import java.lang.reflect.Method;
    import org.qi4j.api.common.AppliesTo;
    import org.qi4j.api.concern.GenericConcern;
    import org.qi4j.api.entity.EntityComposite;
    import org.qi4j.api.injection.scope.Service;
    import org.qi4j.api.injection.scope.This;
    import org.qi4j.library.eventsourcing.domain.api.DomainEvent;
    import org.qi4j.library.eventsourcing.domain.api.DomainEventValue;
    import org.qi4j.library.eventsourcing.domain.api.DomainEvents;

    /**
     * Generate event for event method
     */
    @AppliesTo(DomainEvent.class)
    public class DomainEventCreationConcern
            extends GenericConcern
    {
        @This
        private EntityComposite entity;

        @Service
        private DomainEventFactory domainEventFactory;

        @Override
        public Object invoke( Object proxy, Method method, Object[] args ) throws Throwable
        {
            if (DomainEvents.currentEvent() == null)
            {
                // Create eventValue
                DomainEventValue eventValue = domainEventFactory.createEvent( entity, method.getName(), args );
                DomainEvents.setCurrentEvent( eventValue );
                try
                {
                    return next.invoke( proxy, method, args );
                } finally
                {
                    DomainEvents.setCurrentEvent( null );
                }

            } else
            {
                // This is probably a replay call
                return next.invoke( proxy, method, args );
            }
        }
    }