Spring Framework example source code file (LazyInitTargetSource.java)

This example Spring Framework source code file (LazyInitTargetSource.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Java - Spring Framework tags/keywords

abstractbeanfactorybasedtargetsource, abstractbeanfactorybasedtargetsource, beansexception, beansexception, lazyinittargetsource, lazyinittargetsource, object, object

The Spring Framework LazyInitTargetSource.java source code

/*
 * Copyright 2002-2007 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
 *
 *      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.springframework.aop.target;

import org.springframework.beans.BeansException;

/**
 * {@link org.springframework.aop.TargetSource} that lazily accesses a
 * singleton bean from a {@link org.springframework.beans.factory.BeanFactory}.
 *
 * <p>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 BeanFactory) on startup.
 * <p>For example:
 *
 * <pre class="code">
 * <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></pre>
 *
 * The "serviceTarget" bean will not get initialized until a method on the
 * "service" proxy gets invoked.
 *
 * <p>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
 */
public class LazyInitTargetSource extends AbstractBeanFactoryBasedTargetSource {

	private Object target;


	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) {
	}

}