Switch on @EnableTransactionManagement by default

Fixes gh-576

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/jdbc/DataSourceTransactionManagerAutoConfiguration.java

@@ -23,7 +23,6 @@ import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
-import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingClass;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.core.Ordered;
@@ -58,7 +57,7 @@ public class DataSourceTransactionManagerAutoConfiguration implements Ordered {
 		return new DataSourceTransactionManager(this.dataSource);
 	}
 
-	@ConditionalOnMissingClass(AbstractTransactionManagementConfiguration.class)
+	@ConditionalOnMissingBean(AbstractTransactionManagementConfiguration.class)
 	@Configuration
 	@EnableTransactionManagement
 	protected static class TransactionManagementConfiguration {

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/jdbc/DataSourceTransactionManagerAutoConfigurationTests.java

@@ -21,6 +21,7 @@ import javax.sql.DataSource;
 import org.junit.Test;
 import org.springframework.context.annotation.AnnotationConfigApplicationContext;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
+import org.springframework.transaction.annotation.AbstractTransactionManagementConfiguration;
 import org.springframework.transaction.annotation.EnableTransactionManagement;
 
 import static org.junit.Assert.assertEquals;
@@ -42,6 +43,8 @@ public class DataSourceTransactionManagerAutoConfigurationTests {
 		this.context.refresh();
 		assertNotNull(this.context.getBean(DataSource.class));
 		assertNotNull(this.context.getBean(DataSourceTransactionManager.class));
+		assertNotNull(this.context
+				.getBean(AbstractTransactionManagementConfiguration.class));
 	}
 
 	@Test