/*
* 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.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.
*
* <p>"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.
*
* <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).
*
* <p>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.
* <p>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.
* <p>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.
* <p>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.
* <p>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.
*/
public void destroy() {
if (this.cacheSessionBean) {
synchronized (this.beanInstanceMonitor) {
if (this.beanInstance instanceof EJBObject) {
removeSessionBeanInstance((EJBObject) this.beanInstance);
}
}
}
}
}
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