# TraceConcern.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 org.qi4j.api.common.AppliesTo;
    import org.qi4j.api.composite.Composite;
    import org.qi4j.api.injection.scope.Invocation;
    import org.qi4j.api.injection.scope.This;

    /**
     * The TraceConcern will call the traceEntry(), traceExit() and traceException() methods in the
     * Tracer instance associated with the CompositeType that the TraceConcern is part of.
     * <p>
     * The Trace paradigm is all about tracking the entry and exit (both normal and exceptional ones)
     * of methods. The TraceConcern will be added to all methods that declares the <code>@Trace</code>
     * annotation, with an optional <i>level</i> argument. The <i>level</i> is the threshold of the
     * Tracer instance required to trace the method, i.e. the <i>priority</i> of the Tracer instance
     * must be equal or higher than the <i>level</i> set in the <code>@Trace</code> annotation of the
     * method.
     * </p>
     * <p>
     * If the <i>priority</i> of the <code>Tracer</code> is set to OFF (Integer.MIN_VALUE) then no
     * tracing will happen.
     * </p>
     */
    @AppliesTo( Trace.class )
    public final class TraceConcern extends AbstractTraceConcern
        implements InvocationHandler
    {
        @Invocation private Trace trace;

        public TraceConcern( @This Composite thisComposite )
        {
            super( thisComposite );
        }

        @Override
        protected boolean doTrace()
        {
            return traceService.traceLevel() <= trace.level();
        }
    }