DATAMONGO-464 - Fixed resource synchronization in MongoDbUtils.

MongoDbUtils now correctly returns DB instances for others than the first one bound. So far the lookup for an alternate database resulted in the first one bound to be returned. Polished log statements a bit.

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/core/MongoDbUtils.java

@@ -78,29 +78,36 @@ public abstract class MongoDbUtils {
 	private static DB doGetDB(Mongo mongo, String databaseName, UserCredentials credentials, boolean allowCreate) {
 
 		DbHolder dbHolder = (DbHolder) TransactionSynchronizationManager.getResource(mongo);
+
 		if (dbHolder != null && !dbHolder.isEmpty()) {
-			// pre-bound Mongo DB
+
 			DB db = null;
+
 			if (TransactionSynchronizationManager.isSynchronizationActive() && dbHolder.doesNotHoldNonDefaultDB()) {
-				// Spring transaction management is active ->
-				db = dbHolder.getDB();
+
+				db = dbHolder.getDB(databaseName);
+
 				if (db != null && !dbHolder.isSynchronizedWithTransaction()) {
-					LOGGER.debug("Registering Spring transaction synchronization for existing Mongo DB");
+
+					LOGGER.debug("Registering Spring transaction synchronization for existing MongoDB {}.", databaseName);
+
 					TransactionSynchronizationManager.registerSynchronization(new MongoSynchronization(dbHolder, mongo));
 					dbHolder.setSynchronizedWithTransaction(true);
 				}
 			}
+
 			if (db != null) {
 				return db;
 			}
 		}
 
-		LOGGER.trace("Getting Mongo Database name=[" + databaseName + "]");
-		DB db = mongo.getDB(databaseName);
+		LOGGER.debug("Getting Mongo Database name=[{}]", databaseName);
 
+		DB db = mongo.getDB(databaseName);
 		boolean credentialsGiven = credentials.hasUsername() && credentials.hasPassword();
+
 		if (credentialsGiven && !db.isAuthenticated()) {
-			// Note, can only authenticate once against the same com.mongodb.DB object.
+
 			String username = credentials.getUsername();
 			String password = credentials.hasPassword() ? credentials.getPassword() : null;
 
@@ -113,16 +120,20 @@ public abstract class MongoDbUtils {
 		// Use same Session for further Mongo actions within the transaction.
 		// Thread object will get removed by synchronization at transaction completion.
 		if (TransactionSynchronizationManager.isSynchronizationActive()) {
-			// We're within a Spring-managed transaction, possibly from JtaTransactionManager.
-			LOGGER.debug("Registering Spring transaction synchronization for new Hibernate Session");
+
+			LOGGER.debug("Registering Spring transaction synchronization for MongoDB instance {}.", databaseName);
+
 			DbHolder holderToUse = dbHolder;
+
 			if (holderToUse == null) {
-				holderToUse = new DbHolder(db);
+				holderToUse = new DbHolder(databaseName, db);
 			} else {
-				holderToUse.addDB(db);
+				holderToUse.addDB(databaseName, db);
 			}
+
 			TransactionSynchronizationManager.registerSynchronization(new MongoSynchronization(holderToUse, mongo));
 			holderToUse.setSynchronizedWithTransaction(true);
+
 			if (holderToUse != dbHolder) {
 				TransactionSynchronizationManager.bindResource(mongo, holderToUse);
 			}
@@ -146,6 +157,7 @@ public abstract class MongoDbUtils {
 	 * @return whether the DB is transactional
 	 */
 	public static boolean isDBTransactional(DB db, Mongo mongo) {
+
 		if (mongo == null) {
 			return false;
 		}
@@ -159,6 +171,7 @@ public abstract class MongoDbUtils {
 	 * @param db the DB to close (may be <code>null</code>)
 	 */
 	public static void closeDB(DB db) {
+
 		if (db != null) {
 			LOGGER.debug("Closing Mongo DB object");
 			try {

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/core/MongoDbUtilsUnitTests.java

@@ -0,0 +1,65 @@
+/*
+ * Copyright 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.data.mongodb.core;
+
+import static org.hamcrest.CoreMatchers.*;
+import static org.junit.Assert.*;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+import org.springframework.transaction.support.TransactionSynchronizationManager;
+
+import com.mongodb.DB;
+import com.mongodb.Mongo;
+
+/**
+ * Unit tests for {@link MongoDbUtils}.
+ * 
+ * @author Oliver Gierke
+ */
+public class MongoDbUtilsUnitTests {
+
+	Mongo mongo;
+
+	@Before
+	public void setUp() throws Exception {
+		this.mongo = new Mongo();
+		TransactionSynchronizationManager.initSynchronization();
+	}
+
+	@After
+	public void tearDown() {
+
+		for (Object key : TransactionSynchronizationManager.getResourceMap().keySet()) {
+			TransactionSynchronizationManager.unbindResource(key);
+		}
+
+		TransactionSynchronizationManager.clearSynchronization();
+	}
+
+	@Test
+	public void returnsNewInstanceForDifferentDatabaseName() {
+
+		DB first = MongoDbUtils.getDB(mongo, "first");
+		assertThat(first, is(notNullValue()));
+		assertThat(MongoDbUtils.getDB(mongo, "first"), is(first));
+
+		DB second = MongoDbUtils.getDB(mongo, "second");
+		assertThat(second, is(not(first)));
+		assertThat(MongoDbUtils.getDB(mongo, "second"), is(second));
+	}
+}