Back off if DataSource is not on the classpath

Closes gh-41082

Author: mhalbritter

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

@@ -49,7 +49,7 @@
  */
 @AutoConfiguration(before = TransactionAutoConfiguration.class,
 		after = TransactionManagerCustomizationAutoConfiguration.class)
-@ConditionalOnClass({ JdbcTemplate.class, TransactionManager.class })
+@ConditionalOnClass({ DataSource.class, JdbcTemplate.class, TransactionManager.class })
 @AutoConfigureOrder(Ordered.LOWEST_PRECEDENCE)
 @EnableConfigurationProperties(DataSourceProperties.class)
 public class DataSourceTransactionManagerAutoConfiguration {

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

@@ -25,6 +25,7 @@
 import org.springframework.boot.autoconfigure.AutoConfigurations;
 import org.springframework.boot.autoconfigure.transaction.TransactionAutoConfiguration;
 import org.springframework.boot.autoconfigure.transaction.TransactionManagerCustomizationAutoConfiguration;
+import org.springframework.boot.test.context.FilteredClassLoader;
 import org.springframework.boot.test.context.runner.ApplicationContextRunner;
 import org.springframework.jdbc.datasource.DataSourceTransactionManager;
 import org.springframework.jdbc.support.JdbcTransactionManager;
@@ -40,6 +41,7 @@
  * @author Stephane Nicoll
  * @author Kazuki Shimizu
  * @author Davin Byeon
+ * @author Moritz Halbritter
  */
 class DataSourceTransactionManagerAutoConfigurationTests {
 
@@ -124,4 +126,10 @@ void transactionWithMultipleDataSourcesAndPrimaryCandidateIsConfigured() {
 		});
 	}
 
+	@Test
+	void shouldNotUseDataSourcePropertiesIfDataSourceIsNotOnTheClasspath() {
+		this.contextRunner.withClassLoader(new FilteredClassLoader(DataSource.class))
+			.run((context) -> assertThat(context).doesNotHaveBean(DataSourceProperties.class));
+	}
+
 }