Spring Framework example source code file (LocalSlsbInvokerInterceptor.java)

This example Spring Framework source code file (LocalSlsbInvokerInterceptor.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

could, ejb, ejb, ejbaccessexception, ejbaccessexception, ejblocalobject, ejblocalobject, invocationtargetexception, localslsbinvokerinterceptor, method, method, naming, namingexception, object, reflection, servlet, throwable, web

The Spring Framework LocalSlsbInvokerInterceptor.java source code

/*
 * Copyright 2002-2008 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.access;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;

import javax.ejb.CreateException;
import javax.ejb.EJBLocalHome;
import javax.ejb.EJBLocalObject;
import javax.naming.NamingException;

import org.aopalliance.intercept.MethodInvocation;

/**
 * Invoker for a local Stateless Session Bean.
 * Designed for EJB 2.x, but works for EJB 3 Session Beans as well.
 *
 * <p>Caches the home object, since a local EJB home can never go stale.
 * See {@link org.springframework.jndi.JndiObjectLocator} for info on
 * how to specify the JNDI location of the target EJB.
 *
 * <p>In a bean container, this class is normally best used as a singleton. However,
 * if that bean container pre-instantiates singletons (as do the XML ApplicationContext
 * variants) you may have a problem if the bean container is loaded before the EJB
 * container loads the target EJB. That is because by default the JNDI lookup will be
 * performed in the init method of this class and cached, but the EJB will not have been
 * bound at the target location yet. The best solution is to set the lookupHomeOnStartup
 * property to false, in which case the home will be fetched on first access to the EJB.
 * (This flag is only true by default for backwards compatibility reasons).
 * 
 * @author Rod Johnson
 * @author Juergen Hoeller
 * @see AbstractSlsbInvokerInterceptor#setLookupHomeOnStartup
 * @see AbstractSlsbInvokerInterceptor#setCacheHome
 */
public class LocalSlsbInvokerInterceptor extends AbstractSlsbInvokerInterceptor {

	private volatile boolean homeAsComponent = false;


	/**
	 * This implementation "creates" a new EJB instance for each invocation.
	 * Can be overridden for custom invocation strategies.
	 * <p>Alternatively, override getSessionBeanInstance and
	 * releaseSessionBeanInstance to change EJB instance creation,
	 * for example to hold a single shared EJB instance.
	 */
	public Object invoke(MethodInvocation invocation) throws Throwable {
		EJBLocalObject ejb = null;
		try {
			ejb = getSessionBeanInstance();
			Method method = invocation.getMethod();
			if (method.getDeclaringClass().isInstance(ejb)) {
				// directly implemented
				return method.invoke(ejb, invocation.getArguments());
			}
			else {
				// not directly implemented
				Method ejbMethod = ejb.getClass().getMethod(method.getName(), method.getParameterTypes());
				return ejbMethod.invoke(ejb, invocation.getArguments());
			}
		}
		catch (InvocationTargetException ex) {
			Throwable targetEx = ex.getTargetException();
			if (logger.isDebugEnabled()) {
				logger.debug("Method of local EJB [" + getJndiName() + "] threw exception", targetEx);
			}
			if (targetEx instanceof CreateException) {
				throw new EjbAccessException("Could not create local EJB [" + getJndiName() + "]", targetEx);
			}
			else {
				throw targetEx;
			}
		}
		catch (NamingException ex) {
			throw new EjbAccessException("Failed to locate local EJB [" + getJndiName() + "]", ex);
		}
		catch (IllegalAccessException ex) {
			throw new EjbAccessException("Could not access method [" + invocation.getMethod().getName() +
			    "] of local EJB [" + getJndiName() + "]", ex);
		}
		finally {
			releaseSessionBeanInstance(ejb);
		}
	}

	/**
	 * Check for EJB3-style home object that serves as EJB component directly.
	 */
	protected Method getCreateMethod(Object home) throws EjbAccessException {
		if (this.homeAsComponent) {
			return null;
		}
		if (!(home instanceof EJBLocalHome)) {
			// An EJB3 Session Bean...
			this.homeAsComponent = true;
			return null;
		}
		return super.getCreateMethod(home);
	}

	/**
	 * Return an EJB instance to delegate the call to.
	 * Default implementation delegates to newSessionBeanInstance.
	 * @throws NamingException if thrown by JNDI
	 * @throws InvocationTargetException if thrown by the create method
	 * @see #newSessionBeanInstance
	 */
	protected EJBLocalObject getSessionBeanInstance() throws NamingException, InvocationTargetException {
		return newSessionBeanInstance();
	}

	/**
	 * Release the given EJB instance.
	 * Default implementation delegates to removeSessionBeanInstance.
	 * @param ejb the EJB instance to release
	 * @see #removeSessionBeanInstance
	 */
	protected void releaseSessionBeanInstance(EJBLocalObject ejb) {
		removeSessionBeanInstance(ejb);
	}

	/**
	 * Return a new instance of the stateless session bean.
	 * Can be overridden to change the algorithm.
	 * @throws NamingException if thrown by JNDI
	 * @throws InvocationTargetException if thrown by the create method
	 * @see #create
	 */
	protected EJBLocalObject newSessionBeanInstance() throws NamingException, InvocationTargetException {
		if (logger.isDebugEnabled()) {
			logger.debug("Trying to create reference to local EJB");
		}

		// Call superclass to invoke the EJB create method on the cached home.
		Object ejbInstance = create();
		if (!(ejbInstance instanceof EJBLocalObject)) {
			throw new EjbAccessException("EJB instance [" + ejbInstance + "] is not a local SLSB");
		}

		if (logger.isDebugEnabled()) {
			logger.debug("Obtained reference to local EJB: " + ejbInstance);
		}
		return (EJBLocalObject) ejbInstance;
	}

	/**
	 * Remove the given EJB instance.
	 * @param ejb the EJB instance to remove
	 * @see javax.ejb.EJBLocalObject#remove()
	 */
	protected void removeSessionBeanInstance(EJBLocalObject ejb) {
		if (ejb != null && !this.homeAsComponent) {
			try {
				ejb.remove();
			}
			catch (Throwable ex) {
				logger.warn("Could not invoke 'remove' on local EJB proxy", ex);
			}
		}
	}

}