Null precedence is now supported if the underlying database supports it.

Original pull request #1156
Closes #821

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/SqlGenerator.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 the original author or authors.
+ * Copyright 2017-2022 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.
@@ -51,6 +51,7 @@ import java.util.stream.Collectors;
  * @author Milan Milanov
  * @author Myeonghyeon Lee
  * @author Mikhail Polivakha
+ * @author Chirag Tailor
  */
 class SqlGenerator {
 
@@ -714,7 +715,7 @@ class SqlGenerator {
 
 		SqlIdentifier columnName = this.entity.getRequiredPersistentProperty(order.getProperty()).getColumnName();
 		Column column = Column.create(columnName, this.getTable());
-		return OrderByField.from(column, order.getDirection());
+		return OrderByField.from(column, order.getDirection()).withNullHandling(order.getNullHandling());
 	}
 
 	/**

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

@@ -257,6 +257,21 @@ class JdbcAggregateTemplateIntegrationTests {
 				.containsExactly("Star");
 	}
 
+	@Test // GH-821
+	@EnabledOnFeature({SUPPORTS_QUOTED_IDS, SUPPORTS_NULL_HANDLING})
+	void saveAndLoadManyEntitiesWithReferencedEntitySortedWithNullHandling() {
+
+		template.save(createLegoSet(null));
+		template.save(createLegoSet("Star"));
+		template.save(createLegoSet("Frozen"));
+
+		Iterable<LegoSet> reloadedLegoSets = template.findAll(LegoSet.class, Sort.by(new Sort.Order(Sort.Direction.ASC, "name", Sort.NullHandling.NULLS_LAST)));
+
+		assertThat(reloadedLegoSets) //
+				.extracting("name") //
+				.containsExactly("Frozen", "Star", null);
+	}
+
 	@Test // DATAJDBC-112
 	@EnabledOnFeature(SUPPORTS_QUOTED_IDS)
 	void saveAndLoadManyEntitiesByIdWithReferencedEntity() {

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 the original author or authors.
+ * Copyright 2017-2022 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.
@@ -25,7 +25,6 @@ import java.util.Set;
 
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
-
 import org.springframework.data.annotation.Id;
 import org.springframework.data.annotation.ReadOnlyProperty;
 import org.springframework.data.annotation.Version;
@@ -64,6 +63,7 @@ import org.springframework.data.relational.core.sql.Table;
  * @author Milan Milanov
  * @author Myeonghyeon Lee
  * @author Mikhail Polivakha
+ * @author Chirag Tailor
  */
 class SqlGeneratorUnitTests {
 
@@ -245,6 +245,26 @@ class SqlGeneratorUnitTests {
 				"x_other ASC");
 	}
 
+	@Test // GH-821
+	void findAllSortedWithNullHandling_resolvesNullHandlingWhenDialectSupportsIt() {
+
+		SqlGenerator sqlGenerator = createSqlGenerator(DummyEntity.class, PostgresDialect.INSTANCE);
+
+		String sql = sqlGenerator.getFindAll(Sort.by(new Sort.Order(Sort.Direction.ASC, "name", Sort.NullHandling.NULLS_LAST)));
+
+		assertThat(sql).contains("ORDER BY \"dummy_entity\".\"x_name\" ASC NULLS LAST");
+	}
+
+	@Test // GH-821
+	void findAllSortedWithNullHandling_ignoresNullHandlingWhenDialectDoesNotSupportIt() {
+
+		SqlGenerator sqlGenerator = createSqlGenerator(DummyEntity.class, SqlServerDialect.INSTANCE);
+
+		String sql = sqlGenerator.getFindAll(Sort.by(new Sort.Order(Sort.Direction.ASC, "name", Sort.NullHandling.NULLS_LAST)));
+
+		assertThat(sql).endsWith("ORDER BY dummy_entity.x_name ASC");
+	}
+
 	@Test // DATAJDBC-101
 	void findAllPagedByUnpaged() {
 

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

@@ -1,5 +1,5 @@
 /*
- * Copyright 2020-2021 the original author or authors.
+ * Copyright 2020-2022 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.
@@ -29,6 +29,7 @@ import org.springframework.jdbc.core.JdbcOperations;
  * presence or absence of features in tests.
  *
  * @author Jens Schauder
+ * @author Chirag Tailor
  */
 public class TestDatabaseFeatures {
 
@@ -83,6 +84,10 @@ public class TestDatabaseFeatures {
 		assumeThat(database).isNotIn(Database.H2, Database.Hsql);
 	}
 
+	private void supportsNullHandling() {
+		assumeThat(database).isNotIn(Database.MySql, Database.MariaDb, Database.SqlServer);
+	}
+
 	public void databaseIs(Database database) {
 		assumeThat(this.database).isEqualTo(database);
 	}
@@ -115,6 +120,7 @@ public class TestDatabaseFeatures {
 		SUPPORTS_ARRAYS(TestDatabaseFeatures::supportsArrays), //
 		SUPPORTS_GENERATED_IDS_IN_REFERENCED_ENTITIES(TestDatabaseFeatures::supportsGeneratedIdsInReferencedEntities), //
 		SUPPORTS_NANOSECOND_PRECISION(TestDatabaseFeatures::supportsNanosecondPrecision), //
+		SUPPORTS_NULL_HANDLING(TestDatabaseFeatures::supportsNullHandling),
 		IS_POSTGRES(f -> f.databaseIs(Database.PostgreSql)), //
 		IS_HSQL(f -> f.databaseIs(Database.Hsql));