diff --git a/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration.java b/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration.java
index d8819c65b8..3c36b86b00 100644
--- a/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration.java
+++ b/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceConfiguration.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2012-2017 the original author or authors.
+ * Copyright 2012-2018 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.
@@ -37,7 +37,7 @@ import org.springframework.context.annotation.Bean;
 abstract class DataSourceConfiguration {
 
 	@SuppressWarnings("unchecked")
-	protected <T> T createDataSource(DataSourceProperties properties,
+	protected static <T> T createDataSource(DataSourceProperties properties,
 			Class<? extends DataSource> type) {
 		return (T) properties.initializeDataSourceBuilder().type(type).build();
 	}
@@ -46,8 +46,9 @@ abstract class DataSourceConfiguration {
 	 * Tomcat Pool DataSource configuration.
 	 */
 	@ConditionalOnClass(org.apache.tomcat.jdbc.pool.DataSource.class)
+	@ConditionalOnMissingBean(DataSource.class)
 	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.tomcat.jdbc.pool.DataSource", matchIfMissing = true)
-	static class Tomcat extends DataSourceConfiguration {
+	static class Tomcat {
 
 		@Bean
 		@ConfigurationProperties(prefix = "spring.datasource.tomcat")
@@ -71,8 +72,9 @@ abstract class DataSourceConfiguration {
 	 * Hikari DataSource configuration.
 	 */
 	@ConditionalOnClass(HikariDataSource.class)
+	@ConditionalOnMissingBean(DataSource.class)
 	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "com.zaxxer.hikari.HikariDataSource", matchIfMissing = true)
-	static class Hikari extends DataSourceConfiguration {
+	static class Hikari {
 
 		@Bean
 		@ConfigurationProperties(prefix = "spring.datasource.hikari")
@@ -88,9 +90,10 @@ abstract class DataSourceConfiguration {
 	 * @deprecated as of 1.5 in favor of DBCP2
 	 */
 	@ConditionalOnClass(org.apache.commons.dbcp.BasicDataSource.class)
+	@ConditionalOnMissingBean(DataSource.class)
 	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp.BasicDataSource", matchIfMissing = true)
 	@Deprecated
-	static class Dbcp extends DataSourceConfiguration {
+	static class Dbcp {
 
 		@Bean
 		@ConfigurationProperties(prefix = "spring.datasource.dbcp")
@@ -114,8 +117,9 @@ abstract class DataSourceConfiguration {
 	 * DBCP DataSource configuration.
 	 */
 	@ConditionalOnClass(org.apache.commons.dbcp2.BasicDataSource.class)
+	@ConditionalOnMissingBean(DataSource.class)
 	@ConditionalOnProperty(name = "spring.datasource.type", havingValue = "org.apache.commons.dbcp2.BasicDataSource", matchIfMissing = true)
-	static class Dbcp2 extends DataSourceConfiguration {
+	static class Dbcp2 {
 
 		@Bean
 		@ConfigurationProperties(prefix = "spring.datasource.dbcp2")