Attempt to detect ddl-auto mode only if necessary

This commit defers the resolution of the default ddl auto mode only when
it is absolutely necessary. This prevents Spring Boot to attempt to get
a connection when it isn't necessary

Closes gh-12374

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

 /*
- * 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.
@@ -17,6 +17,7 @@
 package org.springframework.boot.autoconfigure.orm.jpa;
 
 import java.util.Map;
+import java.util.function.Supplier;
 
 import javax.persistence.EntityManagerFactory;
 import javax.sql.DataSource;
@@ -90,8 +91,9 @@ class DataSourceInitializedPublisher implements BeanPostProcessor {
 		if (this.properties == null) {
 			return true; // better safe than sorry
 		}
-		String defaultDdlAuto = (EmbeddedDatabaseConnection.isEmbedded(dataSource)
-				? "create-drop" : "none");
+		Supplier<String> defaultDdlAuto = () ->
+				EmbeddedDatabaseConnection.isEmbedded(dataSource) ? "create-drop"
+						: "none";
 		Map<String, Object> hibernate = this.properties
 				.getHibernateProperties(new HibernateSettings().ddlAuto(defaultDdlAuto));
 		if (hibernate.containsKey("hibernate.hbm2ddl.auto")) {

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

@@ -21,6 +21,7 @@ import java.util.Collections;
 import java.util.LinkedHashMap;
 import java.util.List;
 import java.util.Map;
+import java.util.function.Supplier;
 
 import javax.sql.DataSource;
 
@@ -116,7 +117,7 @@ class HibernateJpaConfiguration extends JpaBaseConfiguration {
 
 	@Override
 	protected Map<String, Object> getVendorProperties() {
-		String defaultDdlMode = this.defaultDdlAutoProvider
+		Supplier<String> defaultDdlMode = () -> this.defaultDdlAutoProvider
 				.getDefaultDdlAuto(getDataSource());
 		return new LinkedHashMap<>(getProperties()
 				.getHibernateProperties(new HibernateSettings().ddlAuto(defaultDdlMode)

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

@@ -18,6 +18,7 @@ package org.springframework.boot.autoconfigure.orm.jpa;
 
 import java.util.ArrayList;
 import java.util.Collection;
+import java.util.function.Supplier;
 
 import org.hibernate.boot.model.naming.ImplicitNamingStrategy;
 import org.hibernate.boot.model.naming.PhysicalNamingStrategy;
@@ -30,7 +31,7 @@ import org.hibernate.boot.model.naming.PhysicalNamingStrategy;
  */
 public class HibernateSettings {
 
-	private String ddlAuto;
+	private Supplier<String> ddlAuto;
 
 	private ImplicitNamingStrategy implicitNamingStrategy;
 
@@ -38,13 +39,25 @@ public class HibernateSettings {
 
 	private Collection<HibernatePropertiesCustomizer> hibernatePropertiesCustomizers;
 
-	public HibernateSettings ddlAuto(String ddlAuto) {
+	public HibernateSettings ddlAuto(Supplier<String> ddlAuto) {
 		this.ddlAuto = ddlAuto;
 		return this;
 	}
 
+	/**
+	 * Specify the default ddl auto value to use.
+	 * @param ddlAuto the default ddl auto if none is provided
+	 * @return this instance
+	 * @see #ddlAuto(Supplier)
+	 * @deprecated as of 2.0.1 in favour of {@link #ddlAuto(Supplier)}
+	 */
+	@Deprecated
+	public HibernateSettings ddlAuto(String ddlAuto) {
+		return ddlAuto(() -> ddlAuto);
+	}
+
 	public String getDdlAuto() {
-		return this.ddlAuto;
+		return (this.ddlAuto != null ? this.ddlAuto.get() : null);
 	}
 
 	public HibernateSettings implicitNamingStrategy(

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

@@ -22,6 +22,7 @@ import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
+import javax.inject.Provider;
 import javax.sql.DataSource;
 
 import org.hibernate.boot.model.naming.ImplicitNamingStrategy;
@@ -217,7 +218,7 @@ public class JpaProperties {
 			getNaming().applyNamingStrategies(result,
 					settings.getImplicitNamingStrategy(),
 					settings.getPhysicalNamingStrategy());
-			String ddlAuto = determineDdlAuto(existing, settings.getDdlAuto());
+			String ddlAuto = determineDdlAuto(existing, settings::getDdlAuto);
 			if (StringUtils.hasText(ddlAuto) && !"none".equals(ddlAuto)) {
 				result.put("hibernate.hbm2ddl.auto", ddlAuto);
 			}
@@ -243,11 +244,13 @@ public class JpaProperties {
 		}
 
 		private String determineDdlAuto(Map<String, String> existing,
-				String defaultDdlAuto) {
-			String ddlAuto = (this.ddlAuto != null ? this.ddlAuto : defaultDdlAuto);
-			if (!existing.containsKey("hibernate.hbm2ddl.auto")
-					&& !"none".equals(ddlAuto)) {
-				return ddlAuto;
+				Provider<String> defaultDdlAuto) {
+			if (!existing.containsKey("hibernate.hbm2ddl.auto")) {
+				String ddlAuto = (this.ddlAuto != null ? this.ddlAuto
+						: defaultDdlAuto.get());
+				if (!"none".equals(ddlAuto)) {
+					return ddlAuto;
+				}
 			}
 			if (existing.containsKey("hibernate.hbm2ddl.auto")) {
 				return existing.get("hibernate.hbm2ddl.auto");

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

@@ -69,7 +69,7 @@ public class CustomHibernateJpaAutoConfigurationTests {
 				.run((context) -> {
 					JpaProperties bean = context.getBean(JpaProperties.class);
 					Map<String, Object> hibernateProperties = bean.getHibernateProperties(
-							new HibernateSettings().ddlAuto("create-drop"));
+							new HibernateSettings());
 					assertThat(hibernateProperties.get("hibernate.ejb.naming_strategy"))
 							.isNull();
 				});

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

@@ -22,6 +22,7 @@ import java.sql.SQLException;
 import java.util.Collections;
 import java.util.Map;
 import java.util.function.Consumer;
+import java.util.function.Supplier;
 
 import javax.sql.DataSource;
 
@@ -60,7 +61,7 @@ public class JpaPropertiesTests {
 	public void noCustomNamingStrategy() {
 		this.contextRunner.run(assertJpaProperties((properties) -> {
 			Map<String, Object> hibernateProperties = properties
-					.getHibernateProperties(new HibernateSettings().ddlAuto("none"));
+					.getHibernateProperties(new HibernateSettings());
 			assertThat(hibernateProperties)
 					.doesNotContainKeys("hibernate.ejb.naming_strategy");
 			assertThat(hibernateProperties).containsEntry(
@@ -80,7 +81,7 @@ public class JpaPropertiesTests {
 				.run(assertJpaProperties((properties) -> {
 					Map<String, Object> hibernateProperties = properties
 							.getHibernateProperties(
-									new HibernateSettings().ddlAuto("none"));
+									new HibernateSettings());
 					assertThat(hibernateProperties).contains(
 							entry("hibernate.implicit_naming_strategy",
 									"com.example.Implicit"),
@@ -97,7 +98,7 @@ public class JpaPropertiesTests {
 			ImplicitNamingStrategy implicitStrategy = mock(ImplicitNamingStrategy.class);
 			PhysicalNamingStrategy physicalStrategy = mock(PhysicalNamingStrategy.class);
 			Map<String, Object> hibernateProperties = properties
-					.getHibernateProperties(new HibernateSettings().ddlAuto("none")
+					.getHibernateProperties(new HibernateSettings()
 							.implicitNamingStrategy(implicitStrategy)
 							.physicalNamingStrategy(physicalStrategy));
 			assertThat(hibernateProperties).contains(
@@ -120,7 +121,7 @@ public class JpaPropertiesTests {
 							PhysicalNamingStrategy.class);
 					Map<String, Object> hibernateProperties = properties
 							.getHibernateProperties(
-									new HibernateSettings().ddlAuto("none")
+									new HibernateSettings()
 											.implicitNamingStrategy(implicitStrategy)
 											.physicalNamingStrategy(physicalStrategy));
 					assertThat(hibernateProperties).contains(
@@ -154,7 +155,7 @@ public class JpaPropertiesTests {
 					};
 					Map<String, Object> hibernateProperties = properties
 							.getHibernateProperties(
-									new HibernateSettings().ddlAuto("none")
+									new HibernateSettings()
 											.implicitNamingStrategy(implicitStrategy)
 											.physicalNamingStrategy(physicalStrategy)
 											.hibernatePropertiesCustomizers(
@@ -177,7 +178,7 @@ public class JpaPropertiesTests {
 				.run(assertJpaProperties((properties) -> {
 					Map<String, Object> hibernateProperties = properties
 							.getHibernateProperties(
-									new HibernateSettings().ddlAuto("none"));
+									new HibernateSettings());
 					// You can override them as we don't provide any default
 					assertThat(hibernateProperties).contains(
 							entry("hibernate.implicit_naming_strategy",
@@ -193,7 +194,7 @@ public class JpaPropertiesTests {
 	public void useNewIdGeneratorMappingsDefault() {
 		this.contextRunner.run(assertJpaProperties((properties) -> {
 			Map<String, Object> hibernateProperties = properties
-					.getHibernateProperties(new HibernateSettings().ddlAuto("none"));
+					.getHibernateProperties(new HibernateSettings());
 			assertThat(hibernateProperties).containsEntry(
 					AvailableSettings.USE_NEW_ID_GENERATOR_MAPPINGS, "true");
 		}));
@@ -207,7 +208,7 @@ public class JpaPropertiesTests {
 				.run(assertJpaProperties((properties) -> {
 					Map<String, Object> hibernateProperties = properties
 							.getHibernateProperties(
-									new HibernateSettings().ddlAuto("none"));
+									new HibernateSettings());
 					assertThat(hibernateProperties).containsEntry(
 							AvailableSettings.USE_NEW_ID_GENERATOR_MAPPINGS, "false");
 				}));
@@ -248,6 +249,33 @@ public class JpaPropertiesTests {
 				}));
 	}
 
+	@Test
+	public void defaultDdlAutoIsNotInvokedIfPropertyIsSet() {
+		this.contextRunner
+				.withPropertyValues("spring.jpa.hibernate.ddl-auto=validate")
+				.run(assertDefaultDdlAutoNotInvoked("validate"));
+	}
+
+	@Test
+	public void defaultDdlAutoIsNotInvokedIfHibernateSpecificPropertyIsSet() {
+		this.contextRunner
+				.withPropertyValues("spring.jpa.properties.hibernate.hbm2ddl.auto=create")
+				.run(assertDefaultDdlAutoNotInvoked("create"));
+	}
+
+	private ContextConsumer<AssertableApplicationContext> assertDefaultDdlAutoNotInvoked(
+			String expectedDdlAuto) {
+		return assertJpaProperties((properties) -> {
+			Supplier<String> ddlAutoSupplier = mock(Supplier.class);
+			Map<String, Object> hibernateProperties = properties
+					.getHibernateProperties(new HibernateSettings()
+							.ddlAuto(ddlAutoSupplier));
+			assertThat(hibernateProperties).containsEntry(
+					"hibernate.hbm2ddl.auto", expectedDdlAuto);
+			verify(ddlAutoSupplier, never()).get();
+		});
+	}
+
 	@Test
 	public void determineDatabaseWithUnknownUrl() {
 		this.contextRunner.run(assertJpaProperties((properties) -> {