+/*
+ * Copyright 2005-2010 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.wamblee.test.transactions;
+
+
+import java.lang.reflect.InvocationHandler;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Method;
+import java.lang.reflect.Proxy;
+
+import javax.persistence.EntityManager;
+
+import org.wamblee.test.persistence.JpaBuilder;
+import org.wamblee.test.persistence.JpaBuilder.JpaUnitOfWork;
+
+/**
+ * This utility makes sure that each invocation on a certain interface is
+ * carried out within a JPA unit of work. Note that this is equivalent
+ * to the sementics of a requiresNew transaction attribute.
+ *
+ * Use {@link #getTransactionScopedEntityManager()} to get the transaction
+ * scoped entity manager to pass to services.
+ *
+ *
+ * For example:
+ * <pre>
+ * JpaBuilder builder = ...
+ * TransactionProxyFactory<Service> factory = new TransactionProxyFactory<Service>(
+ * builder, Service.class);
+ * Service service = new JpaService(factory.getTransactionScopedEntityManager());
+ * Service proxy = factory.getProxy(service);
+ * proxy.executeMethod(...);
+ * </pre>
+ * The above example executes the executeMethod() call on the service object within an active transaction.
+ * In the constructor of the service a transaction scoped entity manager is passed.
+ *
+ * @param T
+ * Type of interface to proxy.
+ *
+ * @author Erik Brakkee
+ */
+public class TransactionProxyFactory<T> {
+
+ /**
+ * Executes the call on the service within a new transaction.
+ *
+ * @author Erik Brakkee
+ *
+ * @param <T> Type of the service interface.
+ */
+ private class UnitOfWorkInvocationHandler<T> implements InvocationHandler {
+
+ private T service;
+
+ public UnitOfWorkInvocationHandler(T aService) {
+ service = aService;
+ }
+
+ @Override
+ public Object invoke(Object aProxy, final Method aMethod,
+ final Object[] aArgs) throws Throwable {
+ return TransactionProxyFactory.this.jpaBuilder
+ .execute(new JpaUnitOfWork<Object>() {
+ @Override
+ public Object execute(EntityManager aEm) throws Exception {
+ EntityManager oldEm = ENTITY_MANAGER.get();
+ try {
+ ENTITY_MANAGER.set(aEm);
+ return aMethod.invoke(service, aArgs);
+ } catch (InvocationTargetException e) {
+ Throwable cause = e.getCause();
+ if (cause instanceof Exception) {
+ throw (Exception) cause;
+ } else if (cause instanceof Error) {
+ throw (Error) cause;
+ }
+ // last resort.
+ throw new RuntimeException(e);
+ } finally {
+ ENTITY_MANAGER.set(oldEm);
+ }
+ }
+ });
+ }
+
+ }
+
+ private static final ThreadSpecificProxyFactory<EntityManager> ENTITY_MANAGER = new ThreadSpecificProxyFactory<EntityManager>(
+ EntityManager.class);
+
+ private JpaBuilder jpaBuilder;
+ private Class<T> clazz;
+
+ /**
+ * Constructs the transaction proxy.
+ *
+ * @param aJpaBuilder
+ */
+ public TransactionProxyFactory(JpaBuilder aJpaBuilder, Class<T> aClass) {
+ jpaBuilder = aJpaBuilder;
+ clazz = aClass;
+ }
+
+ public EntityManager getTransactionScopedEntityManager() {
+ return ENTITY_MANAGER.getProxy();
+ }
+
+ public T getProxy(T aService) {
+ InvocationHandler handler = new UnitOfWorkInvocationHandler<T>(aService);
+ Class proxyClass = Proxy.getProxyClass(clazz.getClassLoader(),
+ new Class[] { clazz });
+ T proxy;
+ try {
+ proxy = (T) proxyClass.getConstructor(
+ new Class[] { InvocationHandler.class }).newInstance(
+ new Object[] { handler });
+ return proxy;
+ } catch (Exception e) {
+ throw new RuntimeException("Could not create proxy for " +
+ clazz.getName(), e);
+ }
+ }
+}