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Spring Framework example source code file (ObjectFactoryCreatingFactoryBean.java)

This example Spring Framework source code file (ObjectFactoryCreatingFactoryBean.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

abstractfactorybean, abstractfactorybean, beansexception, beansexception, class, exception, object, object, objectfactory, objectfactorycreatingfactorybean, objectfactorycreatingfactorybean, property, string

The Spring Framework ObjectFactoryCreatingFactoryBean.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.beans.factory.config;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.util.Assert;

/**
 * A {@link org.springframework.beans.factory.FactoryBean} implementation that
 * returns a value which is an {@link org.springframework.beans.factory.ObjectFactory}
 * that in turn returns a bean sourced from a {@link org.springframework.beans.factory.BeanFactory}.
 *
 * <p>As such, this may be used to avoid having a client object directly calling
 * {@link org.springframework.beans.factory.BeanFactory#getBean(String)} to get
 * a (typically prototype) bean from a
 * {@link org.springframework.beans.factory.BeanFactory}, which would be a
 * violation of the inversion of control principle. Instead, with the use
 * of this class, the client object can be fed an
 * {@link org.springframework.beans.factory.ObjectFactory} instance as a
 * property which directly returns only the one target bean (again, which is
 * typically a prototype bean).
 *
 * <p>A sample config in an XML-based
 * {@link org.springframework.beans.factory.BeanFactory} might look as follows:
 *
 * <pre class="code"><beans>
 *
 *   <!-- Prototype bean since we have state -->
 *   <bean id="myService" class="a.b.c.MyService" singleton="false"/>
 *
 *   <bean id="myServiceFactory"
 *       class="org.springframework.beans.factory.config.ObjectFactoryCreatingFactoryBean">
 *     <property name="targetBeanName"><idref local="myService"/></property>
 *   </bean>
 *
 *   <bean id="clientBean" class="a.b.c.MyClientBean">
 *     <property name="myServiceFactory" ref="myServiceFactory"/>
 *   </bean>
 *
 *</beans></pre>
 *
 * <p>The attendant MyClientBean class implementation might look
 * something like this:
 *
 * <pre class="code">package a.b.c;
 *
 * import org.springframework.beans.factory.ObjectFactory;
 *
 * public class MyClientBean {
 *
 *   private ObjectFactory myServiceFactory;
 *
 *   public void setMyServiceFactory(ObjectFactory myServiceFactory) {
 *     this.myServiceFactory = myServiceFactory;
 *   }
 *
 *   public void someBusinessMethod() {
 *     // get a 'fresh', brand new MyService instance
 *     MyService service = this.myServiceFactory.getObject();
 *     // use the service object to effect the business logic...
 *   }
 * }</pre>
 *
 * <p>An alternate approach to this application of an object creational pattern
 * would be to use the {@link ServiceLocatorFactoryBean}
 * to source (prototype) beans. The {@link ServiceLocatorFactoryBean} approach
 * has the advantage of the fact that one doesn't have to depend on any
 * Spring-specific interface such as {@link org.springframework.beans.factory.ObjectFactory},
 * but has the disadvantage of requiring runtime class generation. Please do
 * consult the {@link ServiceLocatorFactoryBean ServiceLocatorFactoryBean JavaDoc}
 * for a fuller discussion of this issue.
 *
 * @author Colin Sampaleanu
 * @author Juergen Hoeller
 * @since 1.0.2
 * @see org.springframework.beans.factory.ObjectFactory
 * @see ServiceLocatorFactoryBean
 */
public class ObjectFactoryCreatingFactoryBean extends AbstractFactoryBean {

	private String targetBeanName;


	/**
	 * Set the name of the target bean.
	 * <p>The target does not have to be a prototype bean, but realisticially
	 * always will be (because if the target bean were a singleton, then said
	 * singleton bean could simply be injected straight into the dependent object,
	 * thus obviating the need for the extra level of indirection afforded by
	 * the approach encapsulated by this class). Please note that no exception
	 * will be thrown if the supplied <code>targetBeanName does not
	 * reference a prototype bean.
	 */
	public void setTargetBeanName(String targetBeanName) {
		this.targetBeanName = targetBeanName;
	}

	public void afterPropertiesSet() throws Exception {
		Assert.hasText(this.targetBeanName, "Property 'targetBeanName' is required");
		super.afterPropertiesSet();
	}


	public Class getObjectType() {
		return ObjectFactory.class;
	}

	protected Object createInstance() {
		return new ObjectFactory() {
			public Object getObject() throws BeansException {
				return getTargetBean(targetBeanName);
			}
		};
	}

	/**
	 * Template method for obtaining a target bean instance.
	 * Called by the exposed ObjectFactory's <code>getObject() method.
	 * @param targetBeanName the name of the target bean
	 * @return the target bean instance
	 */
	protected Object getTargetBean(String targetBeanName) {
		return getBeanFactory().getBean(targetBeanName);
	}

}

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