DATACMNS-959 - RepositoryFactorySupport now registers interceptor to detect transactions.

The interceptor discovers whether a transaction was running before the call entered the repository proxy and exposes that fact via ….isSurroundingTransactionActive() for donwstream usage.

Related ticket: DATAJPA-1023.

src/main/java/org/springframework/data/repository/core/support/RepositoryFactorySupport.java

@@ -206,6 +206,7 @@ public abstract class RepositoryFactorySupport implements BeanClassLoaderAware,
 		result.setTarget(target);
 		result.setInterfaces(new Class[] { repositoryInterface, Repository.class });
 
+		result.addAdvice(SurroundingTransactionDetectorMethodInterceptor.INSTANCE);
 		result.addAdvisor(ExposeInvocationInterceptor.ADVISOR);
 
 		if (TRANSACTION_PROXY_TYPE != null) {

src/main/java/org/springframework/data/repository/core/support/SurroundingTransactionDetectorMethodInterceptor.java

@@ -0,0 +1,62 @@
+/*
+ * Copyright 2016 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.data.repository.core.support;
+
+import org.aopalliance.intercept.MethodInterceptor;
+import org.aopalliance.intercept.MethodInvocation;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+/**
+ * {@link MethodInterceptor} detecting whether a transaction is already running and exposing that fact via
+ * {@link #isSurroundingTransactionActive()}. Useful in case subsequent interceptors might create transactions
+ * themselves but downstream components have to find out whether there was one running before the call entered the
+ * proxy.
+ * 
+ * @author Oliver Gierke
+ * @since 1.13
+ * @soundtrack Hendrik Freischlader Trio - Openness (Openness)
+ */
+public enum SurroundingTransactionDetectorMethodInterceptor implements MethodInterceptor {
+
+	INSTANCE;
+
+	private final ThreadLocal<Boolean> SURROUNDING_TX_ACTIVE = new ThreadLocal<Boolean>();
+
+	/**
+	 * Returns whether a transaction was active before the method call entered the repository proxy.
+	 * 
+	 * @return
+	 */
+	public boolean isSurroundingTransactionActive() {
+		return Boolean.TRUE == SURROUNDING_TX_ACTIVE.get();
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.aopalliance.intercept.MethodInterceptor#invoke(org.aopalliance.intercept.MethodInvocation)
+	 */
+	@Override
+	public Object invoke(MethodInvocation invocation) throws Throwable {
+
+		SURROUNDING_TX_ACTIVE.set(TransactionSynchronizationManager.isActualTransactionActive());
+
+		try {
+			return invocation.proceed();
+		} finally {
+			SURROUNDING_TX_ACTIVE.remove();
+		}
+	}
+}