Support for Hibernate naming strategy delegator

hibernate.ejb.naming_strategy_delegator and hibernate.ejb.naming_strategy
cannot be used at the same time but Boot sets the latter automatically.

We now only set the naming strategy if no delegator has been specified
via configuration

Closes gh-3149

spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/orm/jpa/JpaProperties.java

@@ -158,12 +158,14 @@ public class JpaProperties {
 		private Map<String, String> getAdditionalProperties(Map<String, String> existing,
 				DataSource dataSource) {
 			Map<String, String> result = new HashMap<String, String>(existing);
-			if (!isAlreadyProvided(existing, "ejb.naming_strategy")
-					&& this.namingStrategy != null) {
-				result.put("hibernate.ejb.naming_strategy", this.namingStrategy.getName());
-			}
-			else if (this.namingStrategy == null) {
-				result.put("hibernate.ejb.naming_strategy", DEFAULT_NAMING_STRATEGY);
+			if (!isAlreadyProvided(existing, "ejb.naming_strategy_delegator")) {
+				if (!isAlreadyProvided(existing, "ejb.naming_strategy")
+						&& this.namingStrategy != null) {
+					result.put("hibernate.ejb.naming_strategy", this.namingStrategy.getName());
+				}
+				else if (this.namingStrategy == null) {
+					result.put("hibernate.ejb.naming_strategy", DEFAULT_NAMING_STRATEGY);
+				}
 			}
 			String ddlAuto = getOrDeduceDdlAuto(existing, dataSource);
 			if (StringUtils.hasText(ddlAuto) && !"none".equals(ddlAuto)) {

spring-boot-autoconfigure/src/test/java/org/springframework/boot/autoconfigure/orm/jpa/CustomHibernateJpaAutoConfigurationTests.java

@@ -84,6 +84,22 @@ public class CustomHibernateJpaAutoConfigurationTests {
 		assertThat(actual, equalTo("create-drop"));
 	}
 
+	@Test
+	public void testNamingStrategyDelegatorTakesPrecedence() {
+		EnvironmentTestUtils.addEnvironment(this.context,
+				"spring.jpa.properties.hibernate.ejb.naming_strategy_delegator:" +
+						"org.hibernate.cfg.naming.ImprovedNamingStrategyDelegator");
+		this.context.register(TestConfiguration.class,
+				EmbeddedDataSourceConfiguration.class,
+				PropertyPlaceholderAutoConfiguration.class,
+				HibernateJpaAutoConfiguration.class);
+		this.context.refresh();
+		JpaProperties bean = this.context.getBean(JpaProperties.class);
+		DataSource dataSource = this.context.getBean(DataSource.class);
+		assertThat(bean.getHibernateProperties(dataSource).get(
+				"hibernate.ejb.naming_strategy"), nullValue());
+	}
+
 	@Configuration
 	@TestAutoConfigurationPackage(City.class)
 	protected static class TestConfiguration {