Offer a proper replacement for NamingStrategy.INSTANCE.

Closes #1350

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/repository/config/AbstractJdbcConfiguration.java

@@ -44,6 +44,7 @@ import org.springframework.data.mapping.model.SimpleTypeHolder;
 import org.springframework.data.relational.RelationalManagedTypes;
 import org.springframework.data.relational.core.conversion.RelationalConverter;
 import org.springframework.data.relational.core.dialect.Dialect;
+import org.springframework.data.relational.core.mapping.DefaultNamingStrategy;
 import org.springframework.data.relational.core.mapping.NamingStrategy;
 import org.springframework.data.relational.core.mapping.Table;
 import org.springframework.data.util.TypeScanner;
@@ -100,7 +101,7 @@ public class AbstractJdbcConfiguration implements ApplicationContextAware {
 	/**
 	 * Register a {@link JdbcMappingContext} and apply an optional {@link NamingStrategy}.
 	 *
-	 * @param namingStrategy optional {@link NamingStrategy}. Use {@link NamingStrategy#INSTANCE} as fallback.
+	 * @param namingStrategy optional {@link NamingStrategy}. Use {@link org.springframework.data.relational.core.mapping.DefaultNamingStrategy#INSTANCE} as fallback.
 	 * @param customConversions see {@link #jdbcCustomConversions()}.
 	 * @param jdbcManagedTypes JDBC managed types, typically discovered through {@link #jdbcManagedTypes() an entity
 	 *          scan}.
@@ -110,7 +111,7 @@ public class AbstractJdbcConfiguration implements ApplicationContextAware {
 	public JdbcMappingContext jdbcMappingContext(Optional<NamingStrategy> namingStrategy,
 			JdbcCustomConversions customConversions, RelationalManagedTypes jdbcManagedTypes) {
 
-		JdbcMappingContext mappingContext = new JdbcMappingContext(namingStrategy.orElse(NamingStrategy.INSTANCE));
+		JdbcMappingContext mappingContext = new JdbcMappingContext(namingStrategy.orElse(DefaultNamingStrategy.INSTANCE));
 		mappingContext.setSimpleTypeHolder(customConversions.getSimpleTypeHolder());
 		mappingContext.setManagedTypes(jdbcManagedTypes);
 

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/JdbcAggregateTemplateUnitTests.java

@@ -42,7 +42,6 @@ import org.springframework.data.jdbc.core.convert.RelationResolver;
 import org.springframework.data.mapping.callback.EntityCallbacks;
 import org.springframework.data.relational.core.conversion.MutableAggregateChange;
 import org.springframework.data.relational.core.mapping.Column;
-import org.springframework.data.relational.core.mapping.NamingStrategy;
 import org.springframework.data.relational.core.mapping.RelationalMappingContext;
 import org.springframework.data.relational.core.mapping.event.AfterConvertCallback;
 import org.springframework.data.relational.core.mapping.event.AfterDeleteCallback;
@@ -72,7 +71,7 @@ public class JdbcAggregateTemplateUnitTests {
 	@BeforeEach
 	public void setUp() {
 
-		RelationalMappingContext mappingContext = new RelationalMappingContext(NamingStrategy.INSTANCE);
+		RelationalMappingContext mappingContext = new RelationalMappingContext();
 		JdbcConverter converter = new BasicJdbcConverter(mappingContext, relationResolver);
 
 		template = new JdbcAggregateTemplate(eventPublisher, mappingContext, converter, dataAccessStrategy);

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/convert/EntityRowMapperUnitTests.java

@@ -54,6 +54,7 @@ import org.springframework.data.annotation.Transient;
 import org.springframework.data.jdbc.core.mapping.AggregateReference;
 import org.springframework.data.jdbc.core.mapping.JdbcMappingContext;
 import org.springframework.data.mapping.PersistentPropertyPath;
+import org.springframework.data.relational.core.mapping.DefaultNamingStrategy;
 import org.springframework.data.relational.core.mapping.Embedded;
 import org.springframework.data.relational.core.mapping.Embedded.OnEmpty;
 import org.springframework.data.relational.core.mapping.NamingStrategy;
@@ -847,7 +848,7 @@ public class EntityRowMapperUnitTests {
 	}
 
 	private <T> EntityRowMapper<T> createRowMapper(Class<T> type) {
-		return createRowMapper(type, NamingStrategy.INSTANCE);
+		return createRowMapper(type, DefaultNamingStrategy.INSTANCE);
 	}
 
 	@SuppressWarnings("unchecked")

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/mapping/model/DefaultNamingStrategyUnitTests.java

@@ -26,6 +26,7 @@ import org.junit.jupiter.api.Test;
 
 import org.springframework.data.annotation.Id;
 import org.springframework.data.jdbc.core.mapping.JdbcMappingContext;
+import org.springframework.data.relational.core.mapping.DefaultNamingStrategy;
 import org.springframework.data.relational.core.mapping.NamingStrategy;
 import org.springframework.data.relational.core.mapping.RelationalPersistentEntity;
 
@@ -36,9 +37,9 @@ import org.springframework.data.relational.core.mapping.RelationalPersistentEnti
  * @author Jens Schauder
  * @author Mark Paluch
  */
-public class NamingStrategyUnitTests {
+public class DefaultNamingStrategyUnitTests {
 
-	private final NamingStrategy target = NamingStrategy.INSTANCE;
+	private final NamingStrategy target = DefaultNamingStrategy.INSTANCE;
 
 	private final RelationalPersistentEntity<?> persistentEntity = //
 			new JdbcMappingContext(target).getRequiredPersistentEntity(DummyEntity.class);

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/testing/TestConfiguration.java

@@ -41,6 +41,7 @@ import org.springframework.data.jdbc.repository.config.DialectResolver;
 import org.springframework.data.jdbc.repository.support.JdbcRepositoryFactory;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
 import org.springframework.data.relational.core.dialect.Dialect;
+import org.springframework.data.relational.core.mapping.DefaultNamingStrategy;
 import org.springframework.data.relational.core.mapping.NamingStrategy;
 import org.springframework.data.relational.core.mapping.RelationalMappingContext;
 import org.springframework.data.repository.core.NamedQueries;
@@ -114,7 +115,7 @@ public class TestConfiguration {
 	@Bean
 	JdbcMappingContext jdbcMappingContext(Optional<NamingStrategy> namingStrategy, CustomConversions conversions) {
 
-		JdbcMappingContext mappingContext = new JdbcMappingContext(namingStrategy.orElse(NamingStrategy.INSTANCE));
+		JdbcMappingContext mappingContext = new JdbcMappingContext(namingStrategy.orElse(DefaultNamingStrategy.INSTANCE));
 		mappingContext.setSimpleTypeHolder(conversions.getSimpleTypeHolder());
 		return mappingContext;
 	}

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/config/AbstractR2dbcConfiguration.java

@@ -44,6 +44,7 @@ import org.springframework.data.r2dbc.dialect.R2dbcDialect;
 import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
 import org.springframework.data.relational.RelationalManagedTypes;
 import org.springframework.data.relational.core.conversion.BasicRelationalConverter;
+import org.springframework.data.relational.core.mapping.DefaultNamingStrategy;
 import org.springframework.data.relational.core.mapping.NamingStrategy;
 import org.springframework.data.relational.core.mapping.Table;
 import org.springframework.data.util.TypeScanner;
@@ -57,6 +58,7 @@ import org.springframework.util.StringUtils;
  * R2DBC to work.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  * @see ConnectionFactory
  * @see DatabaseClient
  * @see org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories
@@ -161,7 +163,7 @@ public abstract class AbstractR2dbcConfiguration implements ApplicationContextAw
 	/**
 	 * Register a {@link R2dbcMappingContext} and apply an optional {@link NamingStrategy}.
 	 *
-	 * @param namingStrategy optional {@link NamingStrategy}. Use {@link NamingStrategy#INSTANCE} as fallback.
+	 * @param namingStrategy optional {@link NamingStrategy}. Use {@link DefaultNamingStrategy#INSTANCE} as fallback.
 	 * @param r2dbcCustomConversions customized R2DBC conversions.
 	 * @param r2dbcManagedTypes R2DBC managed types, typically discovered through {@link #r2dbcManagedTypes() an entity
 	 *          scan}.
@@ -174,7 +176,7 @@ public abstract class AbstractR2dbcConfiguration implements ApplicationContextAw
 
 		Assert.notNull(namingStrategy, "NamingStrategy must not be null");
 
-		R2dbcMappingContext context = new R2dbcMappingContext(namingStrategy.orElse(NamingStrategy.INSTANCE));
+		R2dbcMappingContext context = new R2dbcMappingContext(namingStrategy.orElse(DefaultNamingStrategy.INSTANCE));
 		context.setSimpleTypeHolder(r2dbcCustomConversions.getSimpleTypeHolder());
 		context.setManagedTypes(r2dbcManagedTypes);
 

spring-data-relational/src/main/java/org/springframework/data/relational/core/mapping/DefaultNamingStrategy.java

@@ -25,6 +25,19 @@ import org.springframework.util.Assert;
  */
 public class DefaultNamingStrategy implements NamingStrategy {
 
+	/**
+	 * Static immutable instance of the class. It is made immutable by letting
+	 * {@link #setForeignKeyNaming(ForeignKeyNaming)} throw an exception.
+	 * <p>
+	 * Using this avoids creating essentially the same class over and over again.
+	 */
+	public static NamingStrategy INSTANCE = new DefaultNamingStrategy() {
+		@Override
+		public void setForeignKeyNaming(ForeignKeyNaming foreignKeyNaming) {
+			throw new UnsupportedOperationException("Cannot update immutable DefaultNamingStrategy");
+		}
+	};
+
 	private ForeignKeyNaming foreignKeyNaming = ForeignKeyNaming.APPLY_RENAMING;
 
 	public void setForeignKeyNaming(ForeignKeyNaming foreignKeyNaming) {

spring-data-relational/src/main/java/org/springframework/data/relational/core/mapping/NamingStrategy.java

@@ -41,12 +41,7 @@ public interface NamingStrategy {
 	 *
 	 * @deprecated use {@link DefaultNamingStrategy#INSTANCE} instead.
 	 */
-	@Deprecated(since = "2.4") NamingStrategy INSTANCE = new DefaultNamingStrategy() {
-		@Override
-		public void setForeignKeyNaming(ForeignKeyNaming foreignKeyNaming) {
-			throw new UnsupportedOperationException("Cannot update immutable DefaultNamingStrategy");
-		}
-	};
+	@Deprecated(since = "2.4", forRemoval = true) NamingStrategy INSTANCE = DefaultNamingStrategy.INSTANCE;
 
 	/**
 	 * Defaults to no schema.

spring-data-relational/src/test/java/org/springframework/data/relational/core/mapping/DefaultNamingStrategyUnitTests.java

@@ -31,9 +31,9 @@ import org.springframework.data.relational.core.mapping.RelationalPersistentEnti
  * @author Oliver Gierke
  * @author Jens Schauder
  */
-public class NamingStrategyUnitTests {
+public class DefaultNamingStrategyUnitTests {
 
-	private final NamingStrategy target = NamingStrategy.INSTANCE;
+	private final NamingStrategy target = DefaultNamingStrategy.INSTANCE;
 	private final RelationalMappingContext context = new RelationalMappingContext(target);
 	private final RelationalPersistentEntity<?> persistentEntity = context.getRequiredPersistentEntity(DummyEntity.class);