# AbstractTraceConcern.java

    /*
     * Copyright 2006 Niclas Hedhman.
     *
     * 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.logging.trace;

    import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.Method;
    import org.qi4j.api.Qi4j;
    import org.qi4j.api.common.Optional;
    import org.qi4j.api.composite.Composite;
    import org.qi4j.api.concern.ConcernOf;
    import org.qi4j.api.injection.scope.Service;
    import org.qi4j.api.injection.scope.Structure;
    import org.qi4j.logging.trace.service.TraceService;

    public abstract class AbstractTraceConcern extends ConcernOf<InvocationHandler>
        implements InvocationHandler
    {
        @Structure private Qi4j api;
        @Optional @Service protected TraceService traceService;
        private Composite thisComposite;
        private Class compositeType;

        public AbstractTraceConcern( Composite thisComposite )
        {
            this.thisComposite = thisComposite;
            compositeType = thisComposite.getClass().getInterfaces()[ 0 ];
        }

        @Override
        public Object invoke( Object proxy, Method method, Object[] args )
            throws Throwable
        {
            boolean doTrace = traceService != null && doTrace();
            Object result;
            long entryTime = 0;
            long timeStamp = 0;
            try
            {
                if( doTrace )
                {
                    entryTime = System.currentTimeMillis();
                    timeStamp = System.nanoTime();
                }
                result = next.invoke( proxy, method, args );
                if( doTrace )
                {
                    long duration = System.nanoTime() - timeStamp;
                    traceService.traceSuccess( compositeType, api.dereference( thisComposite ), method, args, result, entryTime, duration );
                }
            }
            catch( Throwable t )
            {
                if( doTrace )
                {
                    long duration = System.nanoTime() - timeStamp;
                    Composite object = api.dereference( thisComposite );
                    traceService.traceException( compositeType, object, method, args, t, entryTime, duration );
                }
                throw t;
            }
            return result;
        }

        protected boolean doTrace()
        {
            return true;
        }
    }