# ConcernsInstance.java

    /*
     * Copyright (c) 2008, Rickard Öberg. All Rights Reserved.
     *
     * 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.runtime.composite;

    import java.lang.reflect.InvocationHandler;
    import java.lang.reflect.InvocationTargetException;
    import java.lang.reflect.Method;

    /**
     * JAVADOC
     */
    public final class ConcernsInstance
        implements InvocationHandler
    {
        private final InvocationHandler firstConcern;
        private final FragmentInvocationHandler mixinInvocationHandler;
        private final ProxyReferenceInvocationHandler proxyHandler;

        public ConcernsInstance( InvocationHandler firstConcern,
                                 FragmentInvocationHandler mixinInvocationHandler,
                                 ProxyReferenceInvocationHandler proxyHandler
        )
        {
            this.firstConcern = firstConcern;
            this.mixinInvocationHandler = mixinInvocationHandler;
            this.proxyHandler = proxyHandler;
        }

        public boolean isEmpty()
        {
            return firstConcern == mixinInvocationHandler;
        }

        @Override
        public Object invoke( Object proxy, Method method, Object[] params )
            throws Throwable
        {
            proxyHandler.setProxy( proxy );
            try
            {
                return firstConcern.invoke( proxy, method, params );
            }
            catch( InvocationTargetException e )
            {
                throw e.getTargetException();
            }
            finally
            {
                proxyHandler.clearProxy();
            }
        }
    }