001/*
002 * Copyright 2002-2007 the original author or authors.
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 *      https://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.springframework.beans.factory.serviceloader;
018
019import java.util.ServiceLoader;
020
021import org.springframework.beans.factory.BeanClassLoaderAware;
022import org.springframework.beans.factory.config.AbstractFactoryBean;
023import org.springframework.util.Assert;
024import org.springframework.util.ClassUtils;
025
026/**
027 * Abstract base class for FactoryBeans operating on the
028 * JDK 1.6 {@link java.util.ServiceLoader} facility.
029 *
030 * @author Juergen Hoeller
031 * @since 2.5
032 * @see java.util.ServiceLoader
033 */
034public abstract class AbstractServiceLoaderBasedFactoryBean extends AbstractFactoryBean<Object>
035                implements BeanClassLoaderAware {
036
037        private Class<?> serviceType;
038
039        private ClassLoader beanClassLoader = ClassUtils.getDefaultClassLoader();
040
041
042        /**
043         * Specify the desired service type (typically the service's public API).
044         */
045        public void setServiceType(Class<?> serviceType) {
046                this.serviceType = serviceType;
047        }
048
049        /**
050         * Return the desired service type.
051         */
052        public Class<?> getServiceType() {
053                return this.serviceType;
054        }
055
056        @Override
057        public void setBeanClassLoader(ClassLoader beanClassLoader) {
058                this.beanClassLoader = beanClassLoader;
059        }
060
061
062        /**
063         * Delegates to {@link #getObjectToExpose(java.util.ServiceLoader)}.
064         * @return the object to expose
065         */
066        @Override
067        protected Object createInstance() {
068                Assert.notNull(getServiceType(), "Property 'serviceType' is required");
069                return getObjectToExpose(ServiceLoader.load(getServiceType(), this.beanClassLoader));
070        }
071
072        /**
073         * Determine the actual object to expose for the given ServiceLoader.
074         * <p>Left to concrete subclasses.
075         * @param serviceLoader the ServiceLoader for the configured service class
076         * @return the object to expose
077         */
078        protected abstract Object getObjectToExpose(ServiceLoader<?> serviceLoader);
079
080}