/*
* 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</code> that is eagerly pre-instantiating singleton beans)
* it must be marked as "lazy-init" too, else it will be instantiated by said
* <code>ApplicationContext</code> (or <code>BeanFactory</code>) 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) {
}
}