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/*
 * Copyright 2002-2012 the original author or authors.
 *
 * 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
 *
 *      https://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.springframework.aop.target;

import org.springframework.beans.BeansException;
import org.springframework.lang.Nullable;

/**
 * {@link org.springframework.aop.TargetSource} that lazily accesses a
 * singleton bean from a {@link org.springframework.beans.factory.BeanFactory}.
 *
 * 

Useful when a proxy reference is needed on initialization but * the actual target object should not be initialized until first use. * When the target bean is defined in an * {@link org.springframework.context.ApplicationContext} (or a * {@code BeanFactory} that is eagerly pre-instantiating singleton beans) * it must be marked as "lazy-init" too, else it will be instantiated by said * {@code ApplicationContext} (or {@code BeanFactory}) on startup. *

For example: * *

 * <bean id="serviceTarget" class="example.MyService" lazy-init="true">
 *   ...
 * </bean>
 *
 * <bean id="service" class="org.springframework.aop.framework.ProxyFactoryBean">
 *   <property name="targetSource">
 *     <bean class="org.springframework.aop.target.LazyInitTargetSource">
 *       <property name="targetBeanName"><idref local="serviceTarget"/></property>
 *     </bean>
 *   </property>
 * </bean>
* * The "serviceTarget" bean will not get initialized until a method on the * "service" proxy gets invoked. * *

Subclasses can extend this class and override the {@link #postProcessTargetObject(Object)} to * perform some additional processing with the target object when it is first loaded. * * @author Juergen Hoeller * @author Rob Harrop * @since 1.1.4 * @see org.springframework.beans.factory.BeanFactory#getBean * @see #postProcessTargetObject */ @SuppressWarnings("serial") public class LazyInitTargetSource extends AbstractBeanFactoryBasedTargetSource { @Nullable private Object target; @Override @Nullable public synchronized Object getTarget() throws BeansException { if (this.target == null) { this.target = getBeanFactory().getBean(getTargetBeanName()); postProcessTargetObject(this.target); } return this.target; } /** * Subclasses may override this method to perform additional processing on * the target object when it is first loaded. * @param targetObject the target object that has just been instantiated (and configured) */ protected void postProcessTargetObject(Object targetObject) { } }





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