001: /*
002: * Copyright 2002-2006 the original author or authors.
003: *
004: * Licensed under the Apache License, Version 2.0 (the "License");
005: * you may not use this file except in compliance with the License.
006: * You may obtain a copy of the License at
007: *
008: * http://www.apache.org/licenses/LICENSE-2.0
009: *
010: * Unless required by applicable law or agreed to in writing, software
011: * distributed under the License is distributed on an "AS IS" BASIS,
012: * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013: * See the License for the specific language governing permissions and
014: * limitations under the License.
015: */
016:
017: package org.springframework.ejb.access;
018:
019: import java.lang.reflect.InvocationTargetException;
020: import java.lang.reflect.Method;
021:
022: import javax.ejb.CreateException;
023: import javax.ejb.EJBLocalObject;
024: import javax.naming.NamingException;
025:
026: import org.aopalliance.intercept.MethodInvocation;
027:
028: /**
029: * <p>Invoker for a local Stateless Session Bean.
030: * Caches the home object. A local EJB home can never go stale.
031: *
032: * <p>See {@link org.springframework.jndi.JndiObjectLocator} for info on
033: * how to specify the JNDI location of the target EJB.
034: *
035: * <p>In a bean container, this class is normally best used as a singleton. However,
036: * if that bean container pre-instantiates singletons (as do the XML ApplicationContext
037: * variants) you may have a problem if the bean container is loaded before the EJB
038: * container loads the target EJB. That is because by default the JNDI lookup will be
039: * performed in the init method of this class and cached, but the EJB will not have been
040: * bound at the target location yet. The best solution is to set the lookupHomeOnStartup
041: * property to false, in which case the home will be fetched on first access to the EJB.
042: * (This flag is only true by default for backwards compatibility reasons).</p>
043: *
044: * @author Rod Johnson
045: * @author Juergen Hoeller
046: * @see AbstractSlsbInvokerInterceptor#setLookupHomeOnStartup
047: * @see AbstractSlsbInvokerInterceptor#setCacheHome
048: */
049: public class LocalSlsbInvokerInterceptor extends
050: AbstractSlsbInvokerInterceptor {
051:
052: /**
053: * This implementation "creates" a new EJB instance for each invocation.
054: * Can be overridden for custom invocation strategies.
055: * <p>Alternatively, override getSessionBeanInstance and
056: * releaseSessionBeanInstance to change EJB instance creation,
057: * for example to hold a single shared EJB instance.
058: */
059: public Object invoke(MethodInvocation invocation) throws Throwable {
060: EJBLocalObject ejb = null;
061: try {
062: ejb = getSessionBeanInstance();
063: Method method = invocation.getMethod();
064: if (method.getDeclaringClass().isInstance(ejb)) {
065: // directly implemented
066: return method.invoke(ejb, invocation.getArguments());
067: } else {
068: // not directly implemented
069: Method ejbMethod = ejb.getClass().getMethod(
070: method.getName(), method.getParameterTypes());
071: return ejbMethod.invoke(ejb, invocation.getArguments());
072: }
073: } catch (InvocationTargetException ex) {
074: Throwable targetEx = ex.getTargetException();
075: if (logger.isDebugEnabled()) {
076: logger.debug("Method of local EJB [" + getJndiName()
077: + "] threw exception", targetEx);
078: }
079: if (targetEx instanceof CreateException) {
080: throw new EjbAccessException(
081: "Could not create local EJB [" + getJndiName()
082: + "]", targetEx);
083: } else {
084: throw targetEx;
085: }
086: } catch (NamingException ex) {
087: throw new EjbAccessException("Failed to locate local EJB ["
088: + getJndiName() + "]", ex);
089: } catch (IllegalAccessException ex) {
090: throw new EjbAccessException("Could not access method ["
091: + invocation.getMethod().getName()
092: + "] of local EJB [" + getJndiName() + "]", ex);
093: } finally {
094: releaseSessionBeanInstance(ejb);
095: }
096: }
097:
098: /**
099: * Return an EJB instance to delegate the call to.
100: * Default implementation delegates to newSessionBeanInstance.
101: * @throws NamingException if thrown by JNDI
102: * @throws InvocationTargetException if thrown by the create method
103: * @see #newSessionBeanInstance
104: */
105: protected EJBLocalObject getSessionBeanInstance()
106: throws NamingException, InvocationTargetException {
107: return newSessionBeanInstance();
108: }
109:
110: /**
111: * Release the given EJB instance.
112: * Default implementation delegates to removeSessionBeanInstance.
113: * @param ejb the EJB instance to release
114: * @see #removeSessionBeanInstance
115: */
116: protected void releaseSessionBeanInstance(EJBLocalObject ejb) {
117: removeSessionBeanInstance(ejb);
118: }
119:
120: /**
121: * Return a new instance of the stateless session bean.
122: * Can be overridden to change the algorithm.
123: * @throws NamingException if thrown by JNDI
124: * @throws InvocationTargetException if thrown by the create method
125: * @see #create
126: */
127: protected EJBLocalObject newSessionBeanInstance()
128: throws NamingException, InvocationTargetException {
129: if (logger.isDebugEnabled()) {
130: logger.debug("Trying to create reference to local EJB");
131: }
132:
133: // call superclass to invoke the EJB create method on the cached home
134: Object ejbInstance = create();
135: if (!(ejbInstance instanceof EJBLocalObject)) {
136: throw new EjbAccessException("EJB instance [" + ejbInstance
137: + "] is not a local SLSB");
138: }
139:
140: if (logger.isDebugEnabled()) {
141: logger.debug("Obtained reference to local EJB: "
142: + ejbInstance);
143: }
144: return (EJBLocalObject) ejbInstance;
145: }
146:
147: /**
148: * Remove the given EJB instance.
149: * @param ejb the EJB instance to remove
150: * @see javax.ejb.EJBLocalObject#remove
151: */
152: protected void removeSessionBeanInstance(EJBLocalObject ejb) {
153: if (ejb != null) {
154: try {
155: ejb.remove();
156: } catch (Throwable ex) {
157: logger.warn(
158: "Could not invoke 'remove' on local EJB proxy",
159: ex);
160: }
161: }
162: }
163:
164: }
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