Consider custom authentication database when creating MongoClient

Previously, MongoProperties did not consider the configuration of a
custom authentication database when creating a MongoClient. This
commit updates MongoProperties to use the authentication database
when it is configured, falling back to the normal database when it is
not configured.

Closes gh-2562

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/MongoProperties.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -171,8 +171,10 @@ public class MongoProperties {
 				}
 				List<MongoCredential> credentials = null;
 				if (hasCustomCredentials()) {
+					String database = this.authenticationDatabase == null ? getMongoClientDatabase()
+							: this.authenticationDatabase;
 					credentials = Arrays.asList(MongoCredential.createMongoCRCredential(
-							this.username, getMongoClientDatabase(), this.password));
+							this.username, database, this.password));
 				}
 				String host = this.host == null ? "localhost" : this.host;
 				int port = this.port == null ? DEFAULT_PORT : this.port;

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/mongo/MongoPropertiesTests.java

 /*
- * Copyright 2012-2014 the original author or authors.
+ * Copyright 2012-2015 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.
@@ -79,7 +79,28 @@ public class MongoPropertiesTests {
 		properties.setUsername("user");
 		properties.setPassword("secret".toCharArray());
 		MongoClient client = properties.createMongoClient(null);
-		assertMongoCredential(client.getCredentialsList().get(0), "user", "secret");
+		assertMongoCredential(client.getCredentialsList().get(0), "user", "secret",
+				"test");
+	}
+
+	@Test
+	public void databaseCanBeCustomized() throws UnknownHostException {
+		MongoProperties properties = new MongoProperties();
+		properties.setDatabase("foo");
+		properties.setUsername("user");
+		properties.setPassword("secret".toCharArray());
+		MongoClient client = properties.createMongoClient(null);
+		assertMongoCredential(client.getCredentialsList().get(0), "user", "secret", "foo");
+	}
+
+	@Test
+	public void authenticationDatabaseCanBeCustomized() throws UnknownHostException {
+		MongoProperties properties = new MongoProperties();
+		properties.setAuthenticationDatabase("foo");
+		properties.setUsername("user");
+		properties.setPassword("secret".toCharArray());
+		MongoClient client = properties.createMongoClient(null);
+		assertMongoCredential(client.getCredentialsList().get(0), "user", "secret", "foo");
 	}
 
 	@Test
@@ -94,7 +115,7 @@ public class MongoPropertiesTests {
 		assertServerAddress(allAddresses.get(1), "mongo2.example.com", 23456);
 		List<MongoCredential> credentialsList = client.getCredentialsList();
 		assertEquals(1, credentialsList.size());
-		assertMongoCredential(credentialsList.get(0), "user", "secret");
+		assertMongoCredential(credentialsList.get(0), "user", "secret", "test");
 	}
 
 	private void assertServerAddress(ServerAddress serverAddress, String expectedHost,
@@ -104,9 +125,10 @@ public class MongoPropertiesTests {
 	}
 
 	private void assertMongoCredential(MongoCredential credentials,
-			String expectedUsername, String expectedPassword) {
+			String expectedUsername, String expectedPassword, String expectedSource) {
 		assertThat(credentials.getUserName(), equalTo(expectedUsername));
 		assertThat(credentials.getPassword(), equalTo(expectedPassword.toCharArray()));
+		assertThat(credentials.getSource(), equalTo(expectedSource));
 	}
 
 	@Configuration