# NoopMixin.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.api.mixin;

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

    /**
     * Generic mixin that is a no-op. Can be useful if the functionality
     * of a method is mainly provided by concerns and side-effects.
     */
    public final class NoopMixin
        implements InvocationHandler
    {
        private static final Boolean BOOLEAN_DEFAULT = Boolean.FALSE;
        private static final Short SHORT_DEFAULT = 0;
        private static final Character CHARACTER_DEFAULT = 0;
        private static final Integer INTEGER_DEFAULT = 0;
        private static final Long LONG_DEFAULT = 0L;
        private static final Float FLOAT_DEFAULT = 0f;
        private static final Double DOUBLE_DEFAULT = 0.0;

        @Override
        public Object invoke( Object object, Method method, Object[] args )
            throws Throwable
        {
            Class<?> retType = method.getReturnType();
            if( !retType.isPrimitive() )
            {
                return null;
            }
            if( Void.TYPE == retType )
            {
                return null;
            }
            if( Boolean.TYPE == retType )
            {
                return BOOLEAN_DEFAULT;
            }
            if( Short.TYPE == retType )
            {
                return SHORT_DEFAULT;
            }
            if( Character.TYPE == retType )
            {
                return CHARACTER_DEFAULT;
            }
            if( Integer.TYPE == retType )
            {
                return INTEGER_DEFAULT;
            }
            if( Long.TYPE == retType )
            {
                return LONG_DEFAULT;
            }
            if( Float.TYPE == retType )
            {
                return FLOAT_DEFAULT;
            }
            if( Double.TYPE == retType )
            {
                return DOUBLE_DEFAULT;
            }
            return null;
        }
    }