Add property spring.data.jdbc.dialect

The class valued property allows to configure a dialect, without relying
on a database connection to determine it.

See gh-39941

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

@@ -0,0 +1,44 @@
+/*
+ * Copyright 2024 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.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.springframework.boot.autoconfigure.data.jdbc;
+
+import org.springframework.boot.context.properties.ConfigurationProperties;
+import org.springframework.data.relational.core.dialect.Dialect;
+
+/**
+ * Configuration properties for Spring Data JDBC.
+ *
+ * @author Jens Schauder
+ * @since 3.3
+ */
+@ConfigurationProperties(prefix = "spring.data.jdbc")
+public class JdbcDataProperties {
+
+	/**
+	 * Dialect to use. By default, the dialect is determined by inspecting the database connection.
+	 */
+	private Class<? extends Dialect> dialect;
+
+	public Class<? extends Dialect> getDialect() {
+		return this.dialect;
+	}
+
+	public void setDialect(Class<? extends Dialect> dialect) {
+		this.dialect = dialect;
+	}
+
+}

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

@@ -16,9 +16,11 @@
 
 package org.springframework.boot.autoconfigure.data.jdbc;
 
+import java.lang.reflect.InvocationTargetException;
 import java.util.Optional;
 import java.util.Set;
 
+import org.springframework.beans.factory.BeanCreationException;
 import org.springframework.boot.autoconfigure.AutoConfiguration;
 import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
@@ -28,6 +30,7 @@ import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.domain.EntityScanner;
 import org.springframework.boot.autoconfigure.jdbc.DataSourceTransactionManagerAutoConfiguration;
 import org.springframework.boot.autoconfigure.jdbc.JdbcTemplateAutoConfiguration;
+import org.springframework.boot.context.properties.EnableConfigurationProperties;
 import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
@@ -59,6 +62,7 @@ import org.springframework.transaction.PlatformTransactionManager;
  * @author Andy Wilkinson
  * @author Stephane Nicoll
  * @author Mark Paluch
+ * @author Jens Schauder
  * @since 2.1.0
  * @see EnableJdbcRepositories
  */
@@ -67,6 +71,7 @@ import org.springframework.transaction.PlatformTransactionManager;
 @ConditionalOnClass({ NamedParameterJdbcOperations.class, AbstractJdbcConfiguration.class })
 @ConditionalOnProperty(prefix = "spring.data.jdbc.repositories", name = "enabled", havingValue = "true",
 		matchIfMissing = true)
+@EnableConfigurationProperties(JdbcDataProperties.class)
 public class JdbcRepositoriesAutoConfiguration {
 
 	@Configuration(proxyBeanMethods = false)
@@ -82,8 +87,11 @@ public class JdbcRepositoriesAutoConfiguration {
 
 		private final ApplicationContext applicationContext;
 
-		SpringBootJdbcConfiguration(ApplicationContext applicationContext) {
+		private final JdbcDataProperties properties;
+
+		SpringBootJdbcConfiguration(ApplicationContext applicationContext, JdbcDataProperties properties) {
 			this.applicationContext = applicationContext;
+			this.properties = properties;
 		}
 
 		@Override
@@ -141,6 +149,17 @@ public class JdbcRepositoriesAutoConfiguration {
 		@Bean
 		@ConditionalOnMissingBean
 		public Dialect jdbcDialect(NamedParameterJdbcOperations operations) {
+			if (this.properties.getDialect() != null
+			) {
+				Class<?> dialectType = this.properties.getDialect();
+				try {
+					return (Dialect)dialectType.getDeclaredConstructor().newInstance();
+				}
+				catch (InstantiationException | IllegalAccessException |
+					   InvocationTargetException | NoSuchMethodException e) {
+					throw new BeanCreationException("Couldn't create instance of type " + dialectType, e);
+				}
+			}
 			return super.jdbcDialect(operations);
 		}
 

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

@@ -40,6 +40,7 @@ import org.springframework.data.jdbc.core.JdbcAggregateTemplate;
 import org.springframework.data.jdbc.core.convert.DataAccessStrategy;
 import org.springframework.data.jdbc.core.convert.JdbcConverter;
 import org.springframework.data.jdbc.core.convert.JdbcCustomConversions;
+import org.springframework.data.jdbc.core.dialect.JdbcPostgresDialect;
 import org.springframework.data.jdbc.core.mapping.JdbcMappingContext;
 import org.springframework.data.jdbc.repository.config.AbstractJdbcConfiguration;
 import org.springframework.data.jdbc.repository.config.EnableJdbcRepositories;
@@ -58,6 +59,7 @@ import static org.mockito.Mockito.mock;
  * @author Andy Wilkinson
  * @author Stephane Nicoll
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 class JdbcRepositoriesAutoConfigurationTests {
 
@@ -181,6 +183,18 @@ class JdbcRepositoriesAutoConfigurationTests {
 		allowsUserToDefineCustomBean(DialectConfiguration.class, Dialect.class, "customDialect");
 	}
 
+	@Test
+	void allowsConfigurationOfDialectByProperty() {
+		this.contextRunner.with(database())
+				.withPropertyValues("spring.data.jdbc.dialect:" + JdbcPostgresDialect.class.getName())
+				.withConfiguration(AutoConfigurations.of(JdbcTemplateAutoConfiguration.class,
+						DataSourceTransactionManagerAutoConfiguration.class))
+				.withUserConfiguration(TestConfiguration.class)
+				.run((context) -> {
+					assertThat(context).hasSingleBean(JdbcPostgresDialect.class);
+				});
+	}
+
 	private void allowsUserToDefineCustomBean(Class<?> configuration, Class<?> beanType, String beanName) {
 		this.contextRunner.with(database())
 			.withConfiguration(AutoConfigurations.of(JdbcTemplateAutoConfiguration.class,