Registration of columns for generated keys is now dialect dependent.

Different R2DBC drivers expect generated keys when they are in camel case to be quoted or unquoted.
This can now be controlled by implementing `Dialect.renderForGeneratedKeys`.

Closes: #483
Original pull request: #602.

src/main/java/org/springframework/data/r2dbc/core/DefaultReactiveDataAccessStrategy.java

@@ -55,6 +55,7 @@ import org.springframework.util.CollectionUtils;
  *
  * @author Mark Paluch
  * @author Louis Morgan
+ * @author Jens Schauder
  */
 public class DefaultReactiveDataAccessStrategy implements ReactiveDataAccessStrategy {
 
@@ -360,6 +361,11 @@ public class DefaultReactiveDataAccessStrategy implements ReactiveDataAccessStra
 		return this.mappingContext;
 	}
 
+	@Override
+	public String renderForGeneratedKeys(SqlIdentifier identifier) {
+		return dialect.renderForGeneratedKeys(identifier);
+	}
+
 	private RelationalPersistentEntity<?> getRequiredPersistentEntity(Class<?> typeToRead) {
 		return this.mappingContext.getRequiredPersistentEntity(typeToRead);
 	}

src/main/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplate.java

@@ -88,6 +88,7 @@ import org.springframework.util.Assert;
  *
  * @author Mark Paluch
  * @author Bogdan Ilchyshyn
+ * @author Jens Schauder
  * @since 1.1
  */
 public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAware, ApplicationContextAware {
@@ -633,7 +634,7 @@ public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAw
 						return statement.returnGeneratedValues();
 					}
 
-					return statement.returnGeneratedValues(dataAccessStrategy.toSql(identifierColumns.get(0)));
+					return statement.returnGeneratedValues(dataAccessStrategy.renderForGeneratedKeys(identifierColumns.get(0)));
 				})
 				.map(this.dataAccessStrategy.getConverter().populateIdIfNecessary(entity)) //
 				.all() //

src/main/java/org/springframework/data/r2dbc/core/ReactiveDataAccessStrategy.java

@@ -29,6 +29,7 @@ import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.lang.Nullable;
 import org.springframework.r2dbc.core.Parameter;
 import org.springframework.r2dbc.core.PreparedOperation;
+import org.springframework.util.Assert;
 
 /**
  * Data access strategy that generalizes convenience operations using mapped entities. Typically used internally by
@@ -36,6 +37,7 @@ import org.springframework.r2dbc.core.PreparedOperation;
  * primary keys.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  * @see org.springframework.r2dbc.core.PreparedOperation
  * @deprecated since 1.2 in favor of using direct usage of {@link StatementMapper},
  *             {@link org.springframework.data.r2dbc.query.UpdateMapper} and {@link R2dbcConverter}.
@@ -135,6 +137,19 @@ public interface ReactiveDataAccessStrategy {
 	 */
 	String toSql(SqlIdentifier identifier);
 
+	/**
+	 * Render a {@link SqlIdentifier} in a way suitable for registering it as a generated key with a statement.
+	 * 
+	 * @param identifier to render. Must not be {@literal null}.
+	 * @return rendered identifier. Guaranteed to be not {@literal null}.
+	 */
+	default String renderForGeneratedKeys(SqlIdentifier identifier) {
+
+		Assert.notNull(identifier, "Indentifier must not be null.");
+
+		return identifier.toSql(IdentifierProcessing.NONE);
+	}
+
 	/**
 	 * Interface to retrieve parameters for named parameter processing.
 	 */

src/main/java/org/springframework/data/r2dbc/dialect/H2Dialect.java

@@ -1,9 +1,12 @@
 package org.springframework.data.r2dbc.dialect;
 
+import org.springframework.data.relational.core.sql.SqlIdentifier;
+
 /**
  * An SQL dialect for H2 in Postgres Compatibility mode.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public class H2Dialect extends PostgresDialect {
 
@@ -11,4 +14,9 @@ public class H2Dialect extends PostgresDialect {
 	 * Singleton instance.
 	 */
 	public static final H2Dialect INSTANCE = new H2Dialect();
+
+	@Override
+	public String renderForGeneratedKeys(SqlIdentifier identifier) {
+		return identifier.getReference(getIdentifierProcessing());
+	}
 }

src/main/java/org/springframework/data/r2dbc/dialect/MySqlDialect.java

@@ -28,12 +28,14 @@ import java.util.UUID;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.convert.ReadingConverter;
 import org.springframework.data.convert.WritingConverter;
+import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.r2dbc.core.binding.BindMarkersFactory;
 
 /**
  * An SQL dialect for MySQL.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public class MySqlDialect extends org.springframework.data.relational.core.dialect.MySqlDialect
 		implements R2dbcDialect {
@@ -103,6 +105,11 @@ public class MySqlDialect extends org.springframework.data.relational.core.diale
 		}
 	}
 
+	@Override
+	public String renderForGeneratedKeys(SqlIdentifier identifier) {
+		return identifier.getReference(getIdentifierProcessing());
+	}
+
 	/**
 	 * Simple singleton to convert {@link Boolean}s to their {@link Byte} representation. MySQL does not have a built-in
 	 * boolean type by default, so relies on using a byte instead. {@literal true} maps to {@code 1}.

src/main/java/org/springframework/data/r2dbc/dialect/R2dbcDialect.java

@@ -8,6 +8,7 @@ import java.util.Set;
 import org.springframework.data.mapping.model.SimpleTypeHolder;
 import org.springframework.data.r2dbc.mapping.R2dbcSimpleTypeHolder;
 import org.springframework.data.relational.core.dialect.Dialect;
+import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.r2dbc.core.binding.BindMarkersFactory;
 
 /**
@@ -59,4 +60,16 @@ public interface R2dbcDialect extends Dialect {
 	default Collection<Object> getConverters() {
 		return Collections.emptySet();
 	}
+
+	/**
+	 * Render a {@link SqlIdentifier} in a way suitable for registering it as a generated key with a statement. The
+	 * default implementation renders it as it would render a SQL representation of the identifier, i.e. with quotes where
+	 * applicable.
+	 *
+	 * @param identifier to render. Must not be {@literal null}.
+	 * @return rendered identifier. Guaranteed to be not {@literal null}.
+	 */
+	default String renderForGeneratedKeys(SqlIdentifier identifier) {
+		return identifier.toSql(getIdentifierProcessing());
+	}
 }

src/main/java/org/springframework/data/r2dbc/query/QueryMapper.java

@@ -82,9 +82,10 @@ public class QueryMapper {
 
 	/**
 	 * Render a {@link SqlIdentifier} for SQL usage.
+	 * The resulting String might contain quoting characters.
 	 *
-	 * @param identifier
-	 * @return
+	 * @param identifier the identifier to be rendered.
+	 * @return an identifier String.
 	 * @since 1.1
 	 */
 	public String toSql(SqlIdentifier identifier) {

src/test/java/org/springframework/data/r2dbc/repository/AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,158 @@
+/*
+ * Copyright 2021 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.data.r2dbc.repository;
+
+import static org.assertj.core.api.Assertions.*;
+
+import io.r2dbc.spi.ConnectionFactory;
+import lombok.Getter;
+import lombok.NoArgsConstructor;
+import lombok.Setter;
+import reactor.test.StepVerifier;
+
+import java.time.Duration;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Objects;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.dao.DataAccessException;
+import org.springframework.data.annotation.Id;
+import org.springframework.data.annotation.PersistenceConstructor;
+import org.springframework.data.r2dbc.testing.R2dbcIntegrationTestSupport;
+import org.springframework.data.relational.core.mapping.Column;
+import org.springframework.data.relational.core.mapping.Table;
+import org.springframework.data.repository.reactive.ReactiveCrudRepository;
+import org.springframework.jdbc.core.JdbcTemplate;
+import org.springframework.lang.Nullable;
+
+/**
+ * Abstract base class for integration tests for {@link LegoSetRepository} with table and column names that contain
+ * upper and lower case characters.
+ * 
+ * @author Jens Schauder
+ */
+public abstract class AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests extends R2dbcIntegrationTestSupport {
+
+	@Autowired private LegoSetRepository repository;
+	protected JdbcTemplate jdbc;
+
+	@BeforeEach
+	void before() {
+
+		this.jdbc = createJdbcTemplate(createDataSource());
+
+		try {
+			this.jdbc.execute(getDropTableStatement());
+		} catch (DataAccessException e) {}
+
+		this.jdbc.execute(getCreateTableStatement());
+	}
+
+	/**
+	 * Creates a {@link DataSource} to be used in this test.
+	 *
+	 * @return the {@link DataSource} to be used in this test.
+	 */
+	protected abstract DataSource createDataSource();
+
+	/**
+	 * Creates a {@link ConnectionFactory} to be used in this test.
+	 *
+	 * @return the {@link ConnectionFactory} to be used in this test.
+	 */
+	protected abstract ConnectionFactory createConnectionFactory();
+
+	/**
+	 * Returns the CREATE TABLE statement for table {@code legoset} with the following three columns:
+	 * <ul>
+	 * <li>id integer (primary key), not null, auto-increment</li>
+	 * <li>name varchar(255), nullable</li>
+	 * <li>manual integer, nullable</li>
+	 * </ul>
+	 *
+	 * @return the CREATE TABLE statement for table {@code legoset} with three columns.
+	 */
+	protected abstract String getCreateTableStatement();
+
+	/**
+	 * Returns the the DROP TABLE statement for table {@code LegoSet}.
+	 *
+	 * @return the DROP TABLE statement for table {@code LegoSet}.
+	 */
+	protected abstract String getDropTableStatement();
+
+	@Test
+	void insertAndReadEntities() {
+
+		LegoSet legoSet1 = new LegoSet(null, "SCHAUFELRADBAGGER", 12);
+		LegoSet legoSet2 = new LegoSet(null, "FORSCHUNGSSCHIFF", 13);
+
+		repository.saveAll(Arrays.asList(legoSet1, legoSet2)) //
+				.as(StepVerifier::create) //
+				.expectNextCount(2) //
+				.verifyComplete();
+
+		List<LegoSet> legoSets = repository //
+				.findAll() //
+				.collectList() //
+				.block(Duration.ofMillis(500));
+
+		assertThat(legoSets).containsExactlyInAnyOrder(legoSet1, legoSet2);
+	}
+
+	interface LegoSetRepository extends ReactiveCrudRepository<LegoSet, Integer> {}
+
+	@Getter
+	@Setter
+	@Table("LegoSet")
+	@NoArgsConstructor
+	public static class LegoSet {
+
+		@Nullable @Column("Id") @Id Integer id;
+
+		@Column("Name") String name;
+
+		@Column("Manual") Integer manual;
+
+		@PersistenceConstructor
+		LegoSet(@Nullable Integer id, String name, Integer manual) {
+			this.id = id;
+			this.name = name;
+			this.manual = manual;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o)
+				return true;
+			if (o == null || getClass() != o.getClass())
+				return false;
+			LegoSet legoSet = (LegoSet) o;
+			return Objects.equals(id, legoSet.id) && Objects.equals(name, legoSet.name)
+					&& Objects.equals(manual, legoSet.manual);
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hash(id, name, manual);
+		}
+	}
+}

src/test/java/org/springframework/data/r2dbc/repository/H2R2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,90 @@
+/*
+ * Copyright 2021 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.data.r2dbc.repository;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan.Filter;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
+import org.springframework.data.r2dbc.convert.R2dbcCustomConversions;
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
+import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
+import org.springframework.data.r2dbc.testing.H2TestSupport;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+/**
+ * Integration tests for {@link LegoSetRepository} with table and column names that contain * upper and lower case
+ * characters against H2.
+ *
+ * @author Jens Schauder
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration
+public class H2R2dbcRepositoryWithMixedCaseNamesIntegrationTests
+		extends AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests {
+
+	@Configuration
+	@EnableR2dbcRepositories(considerNestedRepositories = true,
+			includeFilters = @Filter(classes = { LegoSetRepository.class }, type = FilterType.ASSIGNABLE_TYPE))
+	static class IntegrationTestConfiguration extends AbstractR2dbcConfiguration {
+
+		@Bean
+		@Override
+		public ConnectionFactory connectionFactory() {
+			return H2TestSupport.createConnectionFactory();
+		}
+
+		@Override
+		public R2dbcMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy,
+				R2dbcCustomConversions r2dbcCustomConversions) {
+
+			R2dbcMappingContext r2dbcMappingContext = super.r2dbcMappingContext(namingStrategy, r2dbcCustomConversions);
+			r2dbcMappingContext.setForceQuote(true);
+
+			return r2dbcMappingContext;
+		}
+	}
+
+	@Override
+	protected DataSource createDataSource() {
+		return H2TestSupport.createDataSource();
+	}
+
+	@Override
+	protected ConnectionFactory createConnectionFactory() {
+		return H2TestSupport.createConnectionFactory();
+	}
+
+	@Override
+	protected String getCreateTableStatement() {
+		return H2TestSupport.CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+
+	@Override
+	protected String getDropTableStatement() {
+		return H2TestSupport.DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+}

src/test/java/org/springframework/data/r2dbc/repository/MariaDbR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2021 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.data.r2dbc.repository;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan.Filter;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
+import org.springframework.data.r2dbc.convert.R2dbcCustomConversions;
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
+import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
+import org.springframework.data.r2dbc.testing.ExternalDatabase;
+import org.springframework.data.r2dbc.testing.MariaDbTestSupport;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+/**
+ * Integration tests for {@link LegoSetRepository} with table and column names that contain * upper and lower case
+ * characters against MariaDb.
+ *
+ * @author Mark Paluch
+ * @author Zsombor Gegesy
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration
+public class MariaDbR2dbcRepositoryWithMixedCaseNamesIntegrationTests
+		extends AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests {
+
+	@RegisterExtension public static final ExternalDatabase database = MariaDbTestSupport.database();
+
+	@Configuration
+	@EnableR2dbcRepositories(considerNestedRepositories = true,
+			includeFilters = @Filter(classes = { LegoSetRepository.class }, type = FilterType.ASSIGNABLE_TYPE))
+	static class IntegrationTestConfiguration extends AbstractR2dbcConfiguration {
+
+		@Bean
+		@Override
+		public ConnectionFactory connectionFactory() {
+			return MariaDbTestSupport.createConnectionFactory(database);
+		}
+
+		@Override
+		public R2dbcMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy,
+				R2dbcCustomConversions r2dbcCustomConversions) {
+
+			R2dbcMappingContext r2dbcMappingContext = super.r2dbcMappingContext(namingStrategy, r2dbcCustomConversions);
+			r2dbcMappingContext.setForceQuote(true);
+
+			return r2dbcMappingContext;
+		}
+	}
+
+	@Override
+	protected DataSource createDataSource() {
+		return MariaDbTestSupport.createDataSource(database);
+	}
+
+	@Override
+	protected ConnectionFactory createConnectionFactory() {
+		return MariaDbTestSupport.createConnectionFactory(database);
+	}
+
+	@Override
+	protected String getCreateTableStatement() {
+		return MariaDbTestSupport.CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+
+	@Override
+	protected String getDropTableStatement() {
+		return MariaDbTestSupport.DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+}

src/test/java/org/springframework/data/r2dbc/repository/MySqlR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,96 @@
+/*
+ * Copyright 2021 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.data.r2dbc.repository;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.context.annotation.ComponentScan.Filter;
+import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
+import org.springframework.data.r2dbc.convert.R2dbcCustomConversions;
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
+import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
+import org.springframework.data.r2dbc.repository.support.R2dbcRepositoryFactory;
+import org.springframework.data.r2dbc.testing.ExternalDatabase;
+import org.springframework.data.r2dbc.testing.MySqlTestSupport;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+/**
+ * Integration tests for {@link LegoSetRepository} with table and column names that contain
+ *  * upper and lower case characters against MySql.
+ *
+ * @author Mark Paluch
+ * @author Zsombor Gegesy
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration
+public class MySqlR2dbcRepositoryWithMixedCaseNamesIntegrationTests
+		extends AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests {
+
+	@RegisterExtension public static final ExternalDatabase database = MySqlTestSupport.database();
+
+	@Configuration
+	@EnableR2dbcRepositories(considerNestedRepositories = true,
+			includeFilters = @Filter(classes = { LegoSetRepository.class }, type = FilterType.ASSIGNABLE_TYPE))
+	static class IntegrationTestConfiguration extends AbstractR2dbcConfiguration {
+
+		@Bean
+		@Override
+		public ConnectionFactory connectionFactory() {
+			return MySqlTestSupport.createConnectionFactory(database);
+		}
+
+		@Override
+		public R2dbcMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy,
+				R2dbcCustomConversions r2dbcCustomConversions) {
+
+			R2dbcMappingContext r2dbcMappingContext = super.r2dbcMappingContext(namingStrategy, r2dbcCustomConversions);
+			r2dbcMappingContext.setForceQuote(true);
+
+			return r2dbcMappingContext;
+		}
+	}
+
+	@Override
+	protected DataSource createDataSource() {
+		return MySqlTestSupport.createDataSource(database);
+	}
+
+	@Override
+	protected ConnectionFactory createConnectionFactory() {
+		return MySqlTestSupport.createConnectionFactory(database);
+	}
+
+	@Override
+	protected String getCreateTableStatement() {
+		return MySqlTestSupport.CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+
+	@Override
+	protected String getDropTableStatement() {
+		return MySqlTestSupport.DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+}

src/test/java/org/springframework/data/r2dbc/repository/OracleR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2021 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.data.r2dbc.repository;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan.Filter;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
+import org.springframework.data.r2dbc.convert.R2dbcCustomConversions;
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
+import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
+import org.springframework.data.r2dbc.repository.support.R2dbcRepositoryFactory;
+import org.springframework.data.r2dbc.testing.ExternalDatabase;
+import org.springframework.data.r2dbc.testing.OracleTestSupport;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+/**
+ * Integration tests for {@link LegoSetRepository}  with table and column names that contain
+ *  * upper and lower case characters against Oracle.
+ *
+ * @author Jens Schauder
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration
+public class OracleR2dbcRepositoryWithMixedCaseNamesIntegrationTests
+		extends AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests {
+
+	@RegisterExtension public static final ExternalDatabase database = OracleTestSupport.database();
+
+	@Configuration
+	@EnableR2dbcRepositories(considerNestedRepositories = true,
+			includeFilters = @Filter(classes = { LegoSetRepository.class }, type = FilterType.ASSIGNABLE_TYPE))
+	static class IntegrationTestConfiguration extends AbstractR2dbcConfiguration {
+
+		@Bean
+		@Override
+		public ConnectionFactory connectionFactory() {
+			return OracleTestSupport.createConnectionFactory(database);
+		}
+
+		@Override
+		public R2dbcMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy,
+				R2dbcCustomConversions r2dbcCustomConversions) {
+
+			R2dbcMappingContext r2dbcMappingContext = super.r2dbcMappingContext(namingStrategy, r2dbcCustomConversions);
+			r2dbcMappingContext.setForceQuote(true);
+
+			return r2dbcMappingContext;
+		}
+	}
+
+	@Override
+	protected DataSource createDataSource() {
+		return OracleTestSupport.createDataSource(database);
+	}
+
+	@Override
+	protected ConnectionFactory createConnectionFactory() {
+		return OracleTestSupport.createConnectionFactory(database);
+	}
+
+	@Override
+	protected String getCreateTableStatement() {
+		return OracleTestSupport.CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+
+	@Override
+	protected String getDropTableStatement() {
+		return OracleTestSupport.DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+}

src/test/java/org/springframework/data/r2dbc/repository/PostgresR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2021 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.data.r2dbc.repository;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.context.annotation.ComponentScan.Filter;
+import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
+import org.springframework.data.r2dbc.convert.R2dbcCustomConversions;
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
+import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
+import org.springframework.data.r2dbc.repository.support.R2dbcRepositoryFactory;
+import org.springframework.data.r2dbc.testing.ExternalDatabase;
+import org.springframework.data.r2dbc.testing.PostgresTestSupport;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+/**
+ * Integration tests for {@link LegoSetRepository} with table and column names that contain
+ *  * upper and lower case characters against Postgres.
+ *
+ * @author Jens Schauder
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration
+public class PostgresR2dbcRepositoryWithMixedCaseNamesIntegrationTests
+		extends AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests {
+
+	@RegisterExtension public static final ExternalDatabase database = PostgresTestSupport.database();
+
+	@Configuration
+	@EnableR2dbcRepositories(considerNestedRepositories = true,
+			includeFilters = @Filter(classes = { LegoSetRepository.class }, type = FilterType.ASSIGNABLE_TYPE))
+	static class IntegrationTestConfiguration extends AbstractR2dbcConfiguration {
+
+		@Bean
+		@Override
+		public ConnectionFactory connectionFactory() {
+			return PostgresTestSupport.createConnectionFactory(database);
+		}
+
+		@Override
+		public R2dbcMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy,
+				R2dbcCustomConversions r2dbcCustomConversions) {
+
+			R2dbcMappingContext r2dbcMappingContext = super.r2dbcMappingContext(namingStrategy, r2dbcCustomConversions);
+			r2dbcMappingContext.setForceQuote(true);
+
+			return r2dbcMappingContext;
+		}
+	}
+
+	@Override
+	protected DataSource createDataSource() {
+		return PostgresTestSupport.createDataSource(database);
+	}
+
+	@Override
+	protected ConnectionFactory createConnectionFactory() {
+		return PostgresTestSupport.createConnectionFactory(database);
+	}
+
+	@Override
+	protected String getCreateTableStatement() {
+		return PostgresTestSupport.CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+
+	@Override
+	protected String getDropTableStatement() {
+		return PostgresTestSupport.DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+}

src/test/java/org/springframework/data/r2dbc/repository/SqlServerR2dbcRepositoryWithMixedCaseNamesIntegrationTests.java

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2019-2021 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.data.r2dbc.repository;
+
+import io.r2dbc.spi.ConnectionFactory;
+
+import java.util.Optional;
+
+import javax.sql.DataSource;
+
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.api.extension.RegisterExtension;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.ComponentScan.Filter;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.FilterType;
+import org.springframework.data.r2dbc.config.AbstractR2dbcConfiguration;
+import org.springframework.data.r2dbc.convert.R2dbcCustomConversions;
+import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
+import org.springframework.data.r2dbc.repository.config.EnableR2dbcRepositories;
+import org.springframework.data.r2dbc.repository.support.R2dbcRepositoryFactory;
+import org.springframework.data.r2dbc.testing.ExternalDatabase;
+import org.springframework.data.r2dbc.testing.SqlServerTestSupport;
+import org.springframework.data.relational.core.mapping.NamingStrategy;
+import org.springframework.test.context.ContextConfiguration;
+import org.springframework.test.context.junit.jupiter.SpringExtension;
+
+/**
+ * Integration tests for {@link LegoSetRepository} with table and column names that contain
+ *  * upper and lower case characters against SQL-Server.
+ *
+ * @author Jens Schauder
+ */
+@ExtendWith(SpringExtension.class)
+@ContextConfiguration
+public class SqlServerR2dbcRepositoryWithMixedCaseNamesIntegrationTests
+		extends AbstractR2dbcRepositoryWithMixedCaseNamesIntegrationTests {
+
+	@RegisterExtension public static final ExternalDatabase database = SqlServerTestSupport.database();
+
+	@Configuration
+	@EnableR2dbcRepositories(considerNestedRepositories = true,
+			includeFilters = @Filter(classes = { LegoSetRepository.class }, type = FilterType.ASSIGNABLE_TYPE))
+	static class IntegrationTestConfiguration extends AbstractR2dbcConfiguration {
+
+		@Bean
+		@Override
+		public ConnectionFactory connectionFactory() {
+			return SqlServerTestSupport.createConnectionFactory(database);
+		}
+
+		@Override
+		public R2dbcMappingContext r2dbcMappingContext(Optional<NamingStrategy> namingStrategy,
+				R2dbcCustomConversions r2dbcCustomConversions) {
+
+			R2dbcMappingContext r2dbcMappingContext = super.r2dbcMappingContext(namingStrategy, r2dbcCustomConversions);
+			r2dbcMappingContext.setForceQuote(true);
+
+			return r2dbcMappingContext;
+		}
+	}
+
+	@Override
+	protected DataSource createDataSource() {
+		return SqlServerTestSupport.createDataSource(database);
+	}
+
+	@Override
+	protected ConnectionFactory createConnectionFactory() {
+		return SqlServerTestSupport.createConnectionFactory(database);
+	}
+
+	@Override
+	protected String getCreateTableStatement() {
+		return SqlServerTestSupport.CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+
+	@Override
+	protected String getDropTableStatement() {
+		return SqlServerTestSupport.DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES;
+	}
+}

src/test/java/org/springframework/data/r2dbc/testing/ExternalDatabase.java

@@ -222,7 +222,7 @@ public abstract class ExternalDatabase implements BeforeAllCallback {
 		 */
 		@Override
 		public String getHostname() {
-			throw new UnsupportedOperationException(getClass().getSimpleName());
+			return "unknown";
 		}
 
 		/* (non-Javadoc)
@@ -230,7 +230,7 @@ public abstract class ExternalDatabase implements BeforeAllCallback {
 		 */
 		@Override
 		public int getPort() {
-			throw new UnsupportedOperationException(getClass().getSimpleName());
+			return -99999;
 		}
 
 		/* (non-Javadoc)

src/test/java/org/springframework/data/r2dbc/testing/H2TestSupport.java

@@ -28,11 +28,12 @@ import org.springframework.jdbc.datasource.DriverManagerDataSource;
  *
  * @author Mark Paluch
  * @author Bogdan Ilchyshyn
+ * @author Jens Schauder
  */
 public class H2TestSupport {
 
 	public static String CREATE_TABLE_LEGOSET = "CREATE TABLE legoset (\n" //
-			+ "    id          integer CONSTRAINT id PRIMARY KEY,\n" //
+			+ "    id          integer CONSTRAINT id1 PRIMARY KEY,\n" //
 			+ "    version     integer NULL,\n" //
 			+ "    name        varchar(255) NOT NULL,\n" //
 			+ "    manual      integer NULL\n," //
@@ -40,13 +41,21 @@ public class H2TestSupport {
 			+ ");";
 
 	public static String CREATE_TABLE_LEGOSET_WITH_ID_GENERATION = "CREATE TABLE legoset (\n" //
-			+ "    id          serial CONSTRAINT id PRIMARY KEY,\n" //
+			+ "    id          serial CONSTRAINT id1 PRIMARY KEY,\n" //
 			+ "    version     integer NULL,\n" //
 			+ "    name        varchar(255) NOT NULL,\n" //
 			+ "    extra       varchar(255),\n" //
 			+ "    manual      integer NULL\n" //
 			+ ");";
 
+	public static String CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "CREATE TABLE \"LegoSet\" (\n" //
+			+ "    \"Id\"          serial CONSTRAINT id2 PRIMARY KEY,\n" //
+			+ "    \"Name\"        varchar(255) NOT NULL,\n" //
+			+ "    \"Manual\"      integer NULL\n" //
+			+ ");";
+
+	public static final String DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "DROP TABLE \"LegoSet\"";
+
 	/**
 	 * Creates a new {@link ConnectionFactory}.
 	 */

src/test/java/org/springframework/data/r2dbc/testing/MariaDbTestSupport.java

@@ -35,24 +35,33 @@ import org.testcontainers.containers.MariaDBContainer;
  * Utility class for testing against MariaDB.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public class MariaDbTestSupport {
 
 	private static ExternalDatabase testContainerDatabase;
 
-	public static String CREATE_TABLE_LEGOSET = "CREATE TABLE legoset (\n" //
+	public static final String CREATE_TABLE_LEGOSET = "CREATE TABLE legoset (\n" //
 			+ "    id          integer PRIMARY KEY,\n" //
 			+ "    name        varchar(255) NOT NULL,\n" //
 			+ "    manual      integer NULL\n," //
 			+ "    cert        varbinary(255) NULL\n" //
 			+ ") ENGINE=InnoDB;";
 
-	public static String CREATE_TABLE_LEGOSET_WITH_ID_GENERATION = "CREATE TABLE legoset (\n" //
+	public static final String CREATE_TABLE_LEGOSET_WITH_ID_GENERATION = "CREATE TABLE legoset (\n" //
 			+ "    id          integer AUTO_INCREMENT PRIMARY KEY,\n" //
 			+ "    name        varchar(255) NOT NULL,\n" //
 			+ "    manual      integer NULL\n" //
 			+ ") ENGINE=InnoDB;";
 
+	public static final String CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "CREATE TABLE `LegoSet` (\n" //
+			+ "    `Id`          integer AUTO_INCREMENT PRIMARY KEY,\n" //
+			+ "    `Name`        varchar(255) NOT NULL,\n" //
+			+ "    `Manual`      integer NULL\n" //
+			+ ") ENGINE=InnoDB;";
+
+	public static final String DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "DROP TABLE `LegoSet`";
+
 	/**
 	 * Returns a database either hosted locally at {@code localhost:3306/mysql} or running inside Docker.
 	 *

src/test/java/org/springframework/data/r2dbc/testing/MySqlTestSupport.java

@@ -35,6 +35,7 @@ import com.mysql.cj.jdbc.MysqlDataSource;
  *
  * @author Mark Paluch
  * @author Bogdan Ilchyshyn
+ * @author Jens Schauder
  */
 public class MySqlTestSupport {
 
@@ -55,6 +56,14 @@ public class MySqlTestSupport {
 			+ "    manual      integer NULL\n" //
 			+ ") ENGINE=InnoDB;";
 
+
+	public static final String CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "CREATE TABLE `LegoSet` (\n" //
+			+ "    `Id`          integer AUTO_INCREMENT PRIMARY KEY,\n" //
+			+ "    `Name`        varchar(255) NOT NULL,\n" //
+			+ "    `Manual`      integer NULL\n" //
+			+ ") ENGINE=InnoDB;";
+
+	public static final String DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "DROP TABLE LegoSet";
 	/**
 	 * Returns a database either hosted locally or running inside Docker.
 	 *

src/test/java/org/springframework/data/r2dbc/testing/OracleTestSupport.java

@@ -37,6 +37,7 @@ import org.testcontainers.containers.OracleContainer;
  * Utility class for testing against Oracle.
  *
  * @author Mark Paluch
+ * @author Jens Schauder
  */
 public class OracleTestSupport {
 
@@ -57,6 +58,12 @@ public class OracleTestSupport {
 			+ "    manual      INTEGER NULL\n" //
 			+ ")";
 
+	public static final String CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "CREATE TABLE \"LegoSet\" (\n" //
+			+ "    \"Id\"          INTEGER GENERATED by default on null as IDENTITY PRIMARY KEY,\n" //
+			+ "    \"Name\"        VARCHAR2(255) NOT NULL,\n" //
+			+ "    \"Manual\"      INTEGER NULL\n" //
+			+ ")";
+	public static final String DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "DROP TABLE \"LegoSet\"";
 	/**
 	 * Returns a database either hosted locally or running inside Docker.
 	 *

src/test/java/org/springframework/data/r2dbc/testing/PostgresTestSupport.java

@@ -25,7 +25,7 @@ public class PostgresTestSupport {
 	private static ExternalDatabase testContainerDatabase;
 
 	public static String CREATE_TABLE_LEGOSET = "CREATE TABLE legoset (\n" //
-			+ "    id          integer CONSTRAINT id PRIMARY KEY,\n" //
+			+ "    id          integer CONSTRAINT id1 PRIMARY KEY,\n" //
 			+ "    version     integer NULL,\n" //
 			+ "    name        varchar(255) NOT NULL,\n" //
 			+ "    manual      integer NULL\n," //
@@ -33,13 +33,20 @@ public class PostgresTestSupport {
 			+ ");";
 
 	public static String CREATE_TABLE_LEGOSET_WITH_ID_GENERATION = "CREATE TABLE legoset (\n" //
-			+ "    id          serial CONSTRAINT id PRIMARY KEY,\n" //
+			+ "    id          serial CONSTRAINT id1 PRIMARY KEY,\n" //
 			+ "    version     integer NULL,\n" //
 			+ "    name        varchar(255) NOT NULL,\n" //
 			+ "    extra       varchar(255),\n" //
 			+ "    manual      integer NULL\n" //
 			+ ");";
 
+	public static final String CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "CREATE TABLE \"LegoSet\" (\n" //
+			+ "    \"Id\"          serial CONSTRAINT id2 PRIMARY KEY,\n" //
+			+ "    \"Name\"        varchar(255) NOT NULL,\n" //
+			+ "    \"Manual\"      integer NULL\n" //
+			+ ");";
+
+	public static final String DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "DROP TABLE \"LegoSet\"";
 	/**
 	 * Returns a database either hosted locally at {@code postgres:@localhost:5432/postgres} or running inside Docker.
 	 *

src/test/java/org/springframework/data/r2dbc/testing/SqlServerTestSupport.java

@@ -13,9 +13,9 @@ import com.microsoft.sqlserver.jdbc.SQLServerDataSource;
  *
  * @author Mark Paluch
  * @author Bogdan Ilchyshyn
+ * @author Jens Schauder
  */
 public class SqlServerTestSupport {
-
 	public static String CREATE_TABLE_LEGOSET = "CREATE TABLE legoset (\n" //
 			+ "    id          integer PRIMARY KEY,\n" //
 			+ "    version     integer NULL,\n" //
@@ -34,6 +34,14 @@ public class SqlServerTestSupport {
 
 	public static String INSERT_INTO_LEGOSET = "INSERT INTO legoset (id, name, manual) VALUES(@P0, @P1, @P3)";
 
+	public static final String CREATE_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "CREATE TABLE LegoSet (\n" //
+			+ "    Id          integer IDENTITY(1,1) PRIMARY KEY,\n" //
+			+ "    Name        varchar(255) NOT NULL,\n" //
+			+ "    Manual      integer NULL\n" //
+			+ ");";
+
+	public static final String DROP_TABLE_LEGOSET_WITH_MIXED_CASE_NAMES = "DROP TABLE LegoSet";
+
 	/**
 	 * Returns a locally provided database at {@code sqlserver:@localhost:1433/master}.
 	 */