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Spring Framework example source code file (AbstractEnterpriseBean.java)

This example Spring Framework source code file (AbstractEnterpriseBean.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

abstractenterprisebean, bean_factory_path_environment_key, bean_factory_path_environment_key, beanfactory, beanfactorylocator, beanfactoryreference, beanfactoryreference, beanfactoryreferencereleaselistener, beanfactoryreferencereleaselistener, beansexception, contextjndibeanfactorylocator, ejb, fatalbeanexception, servlet, string, string, web

The Spring Framework AbstractEnterpriseBean.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.ejb.support;

import javax.ejb.EnterpriseBean;

import org.springframework.beans.BeansException;
import org.springframework.beans.FatalBeanException;
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.access.BeanFactoryLocator;
import org.springframework.beans.factory.access.BeanFactoryReference;
import org.springframework.context.access.ContextJndiBeanFactoryLocator;
import org.springframework.util.WeakReferenceMonitor;

/**
 * Base class for Spring-based EJB 2.x beans. Not intended for direct subclassing:
 * Extend {@link AbstractStatelessSessionBean}, {@link AbstractStatefulSessionBean}
 * or {@link AbstractMessageDrivenBean} instead.
 *
 * <p>Provides a standard way of loading a Spring BeanFactory. Subclasses act as a
 * facade, with the business logic deferred to beans in the BeanFactory. Default
 * is to use a {@link org.springframework.context.access.ContextJndiBeanFactoryLocator},
 * which will initialize an XML ApplicationContext from the class path (based on a JNDI
 * name specified). For a different locator strategy, <code>setBeanFactoryLocator
 * may be called (<i>before your EJB's ejbCreate method is invoked,
 * e.g. in <code>setSessionContext). For use of a shared ApplicationContext between
 * multiple EJBs, where the container class loader setup supports this visibility, you may
 * instead use a {@link org.springframework.context.access.ContextSingletonBeanFactoryLocator}.
 * Alternatively, {@link #setBeanFactoryLocator} may be called with a custom implementation
 * of the {@link org.springframework.beans.factory.access.BeanFactoryLocator} interface.
 *
 * <p>Note that we cannot use final for our implementation of EJB lifecycle
 * methods, as this would violate the EJB specification.
 *
 * @author Rod Johnson
 * @author Colin Sampaleanu
 * @author Juergen Hoeller
 * @see org.springframework.context.access.ContextJndiBeanFactoryLocator
 * @see org.springframework.context.access.ContextSingletonBeanFactoryLocator
 */
public abstract class AbstractEnterpriseBean implements EnterpriseBean {

	public static final String BEAN_FACTORY_PATH_ENVIRONMENT_KEY = "java:comp/env/ejb/BeanFactoryPath";


	/**
	 * Helper strategy that knows how to locate a Spring BeanFactory (or
	 * ApplicationContext).
	 */
	private BeanFactoryLocator beanFactoryLocator;

	/** factoryKey to be used with BeanFactoryLocator */
	private String beanFactoryLocatorKey;

	/** Spring BeanFactory that provides the namespace for this EJB */
	private BeanFactoryReference beanFactoryReference;


	/**
	 * Set the BeanFactoryLocator to use for this EJB. Default is a
	 * ContextJndiBeanFactoryLocator.
	 * <p>Can be invoked before loadBeanFactory, for example in constructor or
	 * setSessionContext if you want to override the default locator.
	 * <p>Note that the BeanFactory is automatically loaded by the ejbCreate
	 * implementations of AbstractStatelessSessionBean and
	 * AbstractMessageDriverBean but needs to be explicitly loaded in custom
	 * AbstractStatefulSessionBean <code>ejbCreate methods.
	 * @see AbstractStatelessSessionBean#ejbCreate
	 * @see AbstractMessageDrivenBean#ejbCreate
	 * @see AbstractStatefulSessionBean#loadBeanFactory
	 * @see org.springframework.context.access.ContextJndiBeanFactoryLocator
	 */
	public void setBeanFactoryLocator(BeanFactoryLocator beanFactoryLocator) {
		this.beanFactoryLocator = beanFactoryLocator;
	}

	/**
	 * Set the bean factory locator key.
	 * <p>In case of the default BeanFactoryLocator implementation,
	 * ContextJndiBeanFactoryLocator, this is the JNDI path. The default value
	 * of this property is "java:comp/env/ejb/BeanFactoryPath".
	 * <p>Can be invoked before {@link #loadBeanFactory}, for example in the constructor
	 * or <code>setSessionContext if you want to override the default locator key.
	 * @see #BEAN_FACTORY_PATH_ENVIRONMENT_KEY
	 */
	public void setBeanFactoryLocatorKey(String factoryKey) {
		this.beanFactoryLocatorKey = factoryKey;
	}

	/**
	 * Load a Spring BeanFactory namespace. Subclasses must invoke this method.
	 * <p>Package-visible as it shouldn't be called directly by user-created
	 * subclasses.
	 * @see org.springframework.ejb.support.AbstractStatelessSessionBean#ejbCreate()
	 */
	void loadBeanFactory() throws BeansException {
		if (this.beanFactoryLocator == null) {
			this.beanFactoryLocator = new ContextJndiBeanFactoryLocator();
		}
		if (this.beanFactoryLocatorKey == null) {
			this.beanFactoryLocatorKey = BEAN_FACTORY_PATH_ENVIRONMENT_KEY;
		}

		this.beanFactoryReference = this.beanFactoryLocator.useBeanFactory(this.beanFactoryLocatorKey);

		// We cannot rely on the container to call ejbRemove() (it's skipped in
		// the case of system exceptions), so ensure the the bean factory
		// reference is eventually released.
		WeakReferenceMonitor.monitor(this, new BeanFactoryReferenceReleaseListener(this.beanFactoryReference));
	}

	/**
	 * Unload the Spring BeanFactory instance. The default {@link #ejbRemove()}
	 * method invokes this method, but subclasses which override <code>ejbRemove()
	 * must invoke this method themselves.
	 * <p>Package-visible as it shouldn't be called directly by user-created
	 * subclasses.
	 */
	void unloadBeanFactory() throws FatalBeanException {
		// We will not ever get here if the container skips calling ejbRemove(),
		// but the WeakReferenceMonitor will still clean up (later) in that case.
		if (this.beanFactoryReference != null) {
			this.beanFactoryReference.release();
			this.beanFactoryReference = null;
		}
	}

	/**
	 * May be called after <code>ejbCreate().
	 * @return the bean factory
	 */
	protected BeanFactory getBeanFactory() {
		return this.beanFactoryReference.getFactory();
	}

	/**
	 * EJB lifecycle method, implemented to invoke <code>onEjbRemove()
	 * and unload the BeanFactory afterwards.
	 * <p>Don't override it (although it can't be made final): code your shutdown
	 * in {@link #onEjbRemove()}.
	 */
	public void ejbRemove() {
		onEjbRemove();
		unloadBeanFactory();
	}

	/**
	 * Subclasses must implement this method to do any initialization they would
	 * otherwise have done in an <code>ejbRemove() method.
	 * The BeanFactory will be unloaded afterwards.
	 * <p>This implementation is empty, to be overridden in subclasses.
	 * The same restrictions apply to the work of this method as to an
	 * <code>ejbRemove() method.
	 */
	protected void onEjbRemove() {
		// empty
	}


	/**
	 * Implementation of WeakReferenceMonitor's ReleaseListener callback interface.
	 * Release the given BeanFactoryReference if the monitor detects that there
	 * are no strong references to the handle anymore.
	 */
	private static class BeanFactoryReferenceReleaseListener implements WeakReferenceMonitor.ReleaseListener {

		private final BeanFactoryReference beanFactoryReference;

		public BeanFactoryReferenceReleaseListener(BeanFactoryReference beanFactoryReference) {
			this.beanFactoryReference = beanFactoryReference;
		}

		public void released() {
			this.beanFactoryReference.release();
		}
	}

}

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