Remove deprecated SimpleMongoDbFactory call

Update MongoAutoConfiguration to create a `MongoClient` bean rather than
`Mongo` and update `MongoDataAutoConfiguration` to remove the call to
the deprecated `SimpleMongoDbFactory`.

Fixes gh-3105
Closes gh-3126

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/MongoAutoConfiguration.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.
@@ -28,7 +28,7 @@ import org.springframework.boot.context.properties.EnableConfigurationProperties
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 
-import com.mongodb.Mongo;
+import com.mongodb.MongoClient;
 import com.mongodb.MongoClientOptions;
 
 /**
@@ -39,7 +39,7 @@ import com.mongodb.MongoClientOptions;
  * @author Phillip Webb
  */
 @Configuration
-@ConditionalOnClass(Mongo.class)
+@ConditionalOnClass(MongoClient.class)
 @EnableConfigurationProperties(MongoProperties.class)
 @ConditionalOnMissingBean(type = "org.springframework.data.mongodb.MongoDbFactory")
 public class MongoAutoConfiguration {
@@ -50,7 +50,7 @@ public class MongoAutoConfiguration {
 	@Autowired(required = false)
 	private MongoClientOptions options;
 
-	private Mongo mongo;
+	private MongoClient mongo;
 
 	@PreDestroy
 	public void close() {
@@ -61,7 +61,7 @@ public class MongoAutoConfiguration {
 
 	@Bean
 	@ConditionalOnMissingBean
-	public Mongo mongo() throws UnknownHostException {
+	public MongoClient mongo() throws UnknownHostException {
 		this.mongo = this.properties.createMongoClient(this.options);
 		return this.mongo;
 	}

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mongo/MongoDataAutoConfiguration.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.
@@ -42,7 +42,6 @@ import org.springframework.core.type.filter.AnnotationTypeFilter;
 import org.springframework.dao.DataAccessException;
 import org.springframework.dao.support.PersistenceExceptionTranslator;
 import org.springframework.data.annotation.Persistent;
-import org.springframework.data.authentication.UserCredentials;
 import org.springframework.data.mongodb.MongoDbFactory;
 import org.springframework.data.mongodb.core.MongoTemplate;
 import org.springframework.data.mongodb.core.SimpleMongoDbFactory;
@@ -60,6 +59,7 @@ import org.springframework.util.StringUtils;
 
 import com.mongodb.DB;
 import com.mongodb.Mongo;
+import com.mongodb.MongoClient;
 
 /**
  * {@link EnableAutoConfiguration Auto-configuration} for Spring Data's mongo support.
@@ -74,6 +74,7 @@ import com.mongodb.Mongo;
  * @author Oliver Gierke
  * @author Josh Long
  * @author Phillip Webb
+ * @author Eddú Meléndez
  * @since 1.1.0
  */
 @Configuration
@@ -100,15 +101,8 @@ public class MongoDataAutoConfiguration implements BeanClassLoaderAware {
 
 	@Bean
 	@ConditionalOnMissingBean
-	public MongoDbFactory mongoDbFactory(Mongo mongo) throws Exception {
+	public MongoDbFactory mongoDbFactory(MongoClient mongo) throws Exception {
 		String database = this.properties.getMongoClientDatabase();
-		String authDatabase = this.properties.getAuthenticationDatabase();
-		if (StringUtils.hasLength(authDatabase)) {
-			String username = this.properties.getUsername();
-			String password = new String(this.properties.getPassword());
-			UserCredentials credentials = new UserCredentials(username, password);
-			return new SimpleMongoDbFactory(mongo, database, credentials, authDatabase);
-		}
 		return new SimpleMongoDbFactory(mongo, database);
 	}