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/*
 * Copyright 2002-2012 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.rmi.RemoteException;
import javax.ejb.CreateException;
import javax.ejb.EJBObject;
import javax.naming.NamingException;

import org.aopalliance.intercept.MethodInvocation;

import org.springframework.beans.factory.DisposableBean;
import org.springframework.remoting.RemoteLookupFailureException;
import org.springframework.remoting.rmi.RmiClientInterceptorUtils;

/**
 * Basic invoker for a remote Stateless Session Bean.
 * Designed for EJB 2.x, but works for EJB 3 Session Beans as well.
 *
 * 

"Creates" a new EJB instance for each invocation, or caches the session * bean instance for all invocations (see {@link #setCacheSessionBean}). * See {@link org.springframework.jndi.JndiObjectLocator} for info on * how to specify the JNDI location of the target EJB. * *

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). * *

This invoker is typically used with an RMI business interface, which serves * as super-interface of the EJB component interface. Alternatively, this invoker * can also proxy a remote SLSB with a matching non-RMI business interface, i.e. an * interface that mirrors the EJB business methods but does not declare RemoteExceptions. * In the latter case, RemoteExceptions thrown by the EJB stub will automatically get * converted to Spring's unchecked RemoteAccessException. * * @author Rod Johnson * @author Juergen Hoeller * @since 09.05.2003 * @see org.springframework.remoting.RemoteAccessException * @see AbstractSlsbInvokerInterceptor#setLookupHomeOnStartup * @see AbstractSlsbInvokerInterceptor#setCacheHome * @see AbstractRemoteSlsbInvokerInterceptor#setRefreshHomeOnConnectFailure */ public class SimpleRemoteSlsbInvokerInterceptor extends AbstractRemoteSlsbInvokerInterceptor implements DisposableBean { private boolean cacheSessionBean = false; private Object beanInstance; private final Object beanInstanceMonitor = new Object(); /** * Set whether to cache the actual session bean object. *

Off by default for standard EJB compliance. Turn this flag * on to optimize session bean access for servers that are * known to allow for caching the actual session bean object. * @see #setCacheHome */ public void setCacheSessionBean(boolean cacheSessionBean) { this.cacheSessionBean = cacheSessionBean; } /** * This implementation "creates" a new EJB instance for each invocation. * Can be overridden for custom invocation strategies. *

Alternatively, override {@link #getSessionBeanInstance} and * {@link #releaseSessionBeanInstance} to change EJB instance creation, * for example to hold a single shared EJB component instance. */ @Override protected Object doInvoke(MethodInvocation invocation) throws Throwable { Object ejb = null; try { ejb = getSessionBeanInstance(); return RmiClientInterceptorUtils.invokeRemoteMethod(invocation, ejb); } catch (NamingException ex) { throw new RemoteLookupFailureException("Failed to locate remote EJB [" + getJndiName() + "]", ex); } catch (InvocationTargetException ex) { Throwable targetEx = ex.getTargetException(); if (targetEx instanceof RemoteException) { RemoteException rex = (RemoteException) targetEx; throw RmiClientInterceptorUtils.convertRmiAccessException( invocation.getMethod(), rex, isConnectFailure(rex), getJndiName()); } else if (targetEx instanceof CreateException) { throw RmiClientInterceptorUtils.convertRmiAccessException( invocation.getMethod(), targetEx, "Could not create remote EJB [" + getJndiName() + "]"); } throw targetEx; } finally { if (ejb instanceof EJBObject) { releaseSessionBeanInstance((EJBObject) ejb); } } } /** * Return an EJB component instance to delegate the call to. *

The default implementation delegates to {@link #newSessionBeanInstance}. * @return the EJB component instance * @throws NamingException if thrown by JNDI * @throws InvocationTargetException if thrown by the create method * @see #newSessionBeanInstance */ protected Object getSessionBeanInstance() throws NamingException, InvocationTargetException { if (this.cacheSessionBean) { synchronized (this.beanInstanceMonitor) { if (this.beanInstance == null) { this.beanInstance = newSessionBeanInstance(); } return this.beanInstance; } } else { return newSessionBeanInstance(); } } /** * Release the given EJB instance. *

The default implementation delegates to {@link #removeSessionBeanInstance}. * @param ejb the EJB component instance to release * @see #removeSessionBeanInstance */ protected void releaseSessionBeanInstance(EJBObject ejb) { if (!this.cacheSessionBean) { removeSessionBeanInstance(ejb); } } /** * Reset the cached session bean instance, if necessary. */ @Override protected void refreshHome() throws NamingException { super.refreshHome(); if (this.cacheSessionBean) { synchronized (this.beanInstanceMonitor) { this.beanInstance = null; } } } /** * Remove the cached session bean instance, if necessary. */ @Override public void destroy() { if (this.cacheSessionBean) { synchronized (this.beanInstanceMonitor) { if (this.beanInstance instanceof EJBObject) { removeSessionBeanInstance((EJBObject) this.beanInstance); } } } } }





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