Java tutorial
/* Copyright 2017 Penny Rohr Curich 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 guru.qas.martini.event; import org.springframework.beans.BeansException; import org.springframework.beans.factory.BeanFactory; import org.springframework.beans.factory.BeanFactoryAware; import org.springframework.beans.factory.annotation.Value; import org.springframework.beans.factory.config.AutowireCapableBeanFactory; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.context.annotation.Lazy; import static com.google.common.base.Preconditions.checkState; @SuppressWarnings("WeakerAccess") @Configuration @Lazy public class EventManagerConfiguration implements BeanFactoryAware { protected AutowireCapableBeanFactory beanFactory; @Override public void setBeanFactory(BeanFactory beanFactory) throws BeansException { checkState(AutowireCapableBeanFactory.class.isInstance(beanFactory), "BeanFactory must be of type AutowireCapableBeanFactory but found %s", beanFactory.getClass()); this.beanFactory = AutowireCapableBeanFactory.class.cast(beanFactory); } @Bean EventManager getEventManager(@Value("${event.manager.impl:#{null}}") Class<? extends EventManager> impl) { return null == impl ? beanFactory.createBean(DefaultEventManager.class) : beanFactory.createBean(impl); } }