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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.lang.reflect.Method;
import javax.naming.Context;
import javax.naming.NamingException;

import org.aopalliance.intercept.MethodInterceptor;
import org.aopalliance.intercept.MethodInvocation;

import org.springframework.jndi.JndiObjectLocator;

/**
 * Base class for AOP interceptors invoking local or remote Stateless Session Beans.
 * Designed for EJB 2.x, but works for EJB 3 Session Beans as well.
 *
 * 

Such an interceptor must be the last interceptor in the advice chain. * In this case, there is no direct target object: The call is handled in a * special way, getting executed on an EJB instance retrieved via an EJB home. * * @author Rod Johnson * @author Juergen Hoeller */ public abstract class AbstractSlsbInvokerInterceptor extends JndiObjectLocator implements MethodInterceptor { private boolean lookupHomeOnStartup = true; private boolean cacheHome = true; private boolean exposeAccessContext = false; /** * The EJB's home object, potentially cached. * The type must be Object as it could be either EJBHome or EJBLocalHome. */ private Object cachedHome; /** * The no-arg create() method required on EJB homes, potentially cached. */ private Method createMethod; private final Object homeMonitor = new Object(); /** * Set whether to look up the EJB home object on startup. * Default is "true". *

Can be turned off to allow for late start of the EJB server. * In this case, the EJB home object will be fetched on first access. * @see #setCacheHome */ public void setLookupHomeOnStartup(boolean lookupHomeOnStartup) { this.lookupHomeOnStartup = lookupHomeOnStartup; } /** * Set whether to cache the EJB home object once it has been located. * Default is "true". *

Can be turned off to allow for hot restart of the EJB server. * In this case, the EJB home object will be fetched for each invocation. * @see #setLookupHomeOnStartup */ public void setCacheHome(boolean cacheHome) { this.cacheHome = cacheHome; } /** * Set whether to expose the JNDI environment context for all access to the target * EJB, i.e. for all method invocations on the exposed object reference. *

Default is "false", i.e. to only expose the JNDI context for object lookup. * Switch this flag to "true" in order to expose the JNDI environment (including * the authorization context) for each EJB invocation, as needed by WebLogic * for EJBs with authorization requirements. */ public void setExposeAccessContext(boolean exposeAccessContext) { this.exposeAccessContext = exposeAccessContext; } /** * Fetches EJB home on startup, if necessary. * @see #setLookupHomeOnStartup * @see #refreshHome */ @Override public void afterPropertiesSet() throws NamingException { super.afterPropertiesSet(); if (this.lookupHomeOnStartup) { // look up EJB home and create method refreshHome(); } } /** * Refresh the cached home object, if applicable. * Also caches the create method on the home object. * @throws NamingException if thrown by the JNDI lookup * @see #lookup * @see #getCreateMethod */ protected void refreshHome() throws NamingException { synchronized (this.homeMonitor) { Object home = lookup(); if (this.cacheHome) { this.cachedHome = home; this.createMethod = getCreateMethod(home); } } } /** * Determine the create method of the given EJB home object. * @param home the EJB home object * @return the create method * @throws EjbAccessException if the method couldn't be retrieved */ protected Method getCreateMethod(Object home) throws EjbAccessException { try { // Cache the EJB create() method that must be declared on the home interface. return home.getClass().getMethod("create", (Class[]) null); } catch (NoSuchMethodException ex) { throw new EjbAccessException("EJB home [" + home + "] has no no-arg create() method"); } } /** * Return the EJB home object to use. Called for each invocation. *

Default implementation returns the home created on initialization, * if any; else, it invokes lookup to get a new proxy for each invocation. *

Can be overridden in subclasses, for example to cache a home object * for a given amount of time before recreating it, or to test the home * object whether it is still alive. * @return the EJB home object to use for an invocation * @throws NamingException if proxy creation failed * @see #lookup * @see #getCreateMethod */ protected Object getHome() throws NamingException { if (!this.cacheHome || (this.lookupHomeOnStartup && !isHomeRefreshable())) { return (this.cachedHome != null ? this.cachedHome : lookup()); } else { synchronized (this.homeMonitor) { if (this.cachedHome == null) { this.cachedHome = lookup(); this.createMethod = getCreateMethod(this.cachedHome); } return this.cachedHome; } } } /** * Return whether the cached EJB home object is potentially * subject to on-demand refreshing. Default is "false". */ protected boolean isHomeRefreshable() { return false; } /** * Prepares the thread context if necessar, and delegates to * {@link #invokeInContext}. */ @Override public Object invoke(MethodInvocation invocation) throws Throwable { Context ctx = (this.exposeAccessContext ? getJndiTemplate().getContext() : null); try { return invokeInContext(invocation); } finally { getJndiTemplate().releaseContext(ctx); } } /** * Perform the given invocation on the current EJB home, * within the thread context being prepared accordingly. * Template method to be implemented by subclasses. * @param invocation the AOP method invocation * @return the invocation result, if any * @throws Throwable in case of invocation failure */ protected abstract Object invokeInContext(MethodInvocation invocation) throws Throwable; /** * Invokes the {@code create()} method on the cached EJB home object. * @return a new EJBObject or EJBLocalObject * @throws NamingException if thrown by JNDI * @throws InvocationTargetException if thrown by the create method */ protected Object create() throws NamingException, InvocationTargetException { try { Object home = getHome(); Method createMethodToUse = this.createMethod; if (createMethodToUse == null) { createMethodToUse = getCreateMethod(home); } if (createMethodToUse == null) { return home; } // Invoke create() method on EJB home object. return createMethodToUse.invoke(home, (Object[]) null); } catch (IllegalAccessException ex) { throw new EjbAccessException("Could not access EJB home create() method", ex); } } }





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