001/* 002 * Copyright 2002-2012 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.config; 018 019import java.io.Serializable; 020import javax.inject.Provider; 021 022import org.springframework.beans.BeansException; 023import org.springframework.beans.factory.BeanFactory; 024import org.springframework.util.Assert; 025 026/** 027 * A {@link org.springframework.beans.factory.FactoryBean} implementation that 028 * returns a value which is a JSR-330 {@link javax.inject.Provider} that in turn 029 * returns a bean sourced from a {@link org.springframework.beans.factory.BeanFactory}. 030 * 031 * <p>This is basically a JSR-330 compliant variant of Spring's good old 032 * {@link ObjectFactoryCreatingFactoryBean}. It can be used for traditional 033 * external dependency injection configuration that targets a property or 034 * constructor argument of type {@code javax.inject.Provider}, as an 035 * alternative to JSR-330's {@code @Inject} annotation-driven approach. 036 * 037 * @author Juergen Hoeller 038 * @since 3.0.2 039 * @see javax.inject.Provider 040 * @see ObjectFactoryCreatingFactoryBean 041 */ 042public class ProviderCreatingFactoryBean extends AbstractFactoryBean<Provider<Object>> { 043 044 private String targetBeanName; 045 046 047 /** 048 * Set the name of the target bean. 049 * <p>The target does not <i>have</i> to be a non-singleton bean, but realistically 050 * always will be (because if the target bean were a singleton, then said singleton 051 * bean could simply be injected straight into the dependent object, thus obviating 052 * the need for the extra level of indirection afforded by this factory approach). 053 */ 054 public void setTargetBeanName(String targetBeanName) { 055 this.targetBeanName = targetBeanName; 056 } 057 058 @Override 059 public void afterPropertiesSet() throws Exception { 060 Assert.hasText(this.targetBeanName, "Property 'targetBeanName' is required"); 061 super.afterPropertiesSet(); 062 } 063 064 065 @Override 066 public Class<?> getObjectType() { 067 return Provider.class; 068 } 069 070 @Override 071 protected Provider<Object> createInstance() { 072 return new TargetBeanProvider(getBeanFactory(), this.targetBeanName); 073 } 074 075 076 /** 077 * Independent inner class - for serialization purposes. 078 */ 079 @SuppressWarnings("serial") 080 private static class TargetBeanProvider implements Provider<Object>, Serializable { 081 082 private final BeanFactory beanFactory; 083 084 private final String targetBeanName; 085 086 public TargetBeanProvider(BeanFactory beanFactory, String targetBeanName) { 087 this.beanFactory = beanFactory; 088 this.targetBeanName = targetBeanName; 089 } 090 091 @Override 092 public Object get() throws BeansException { 093 return this.beanFactory.getBean(this.targetBeanName); 094 } 095 } 096 097}