Refine embeddable emptiness checks to consider whether the collection holds entities.

Embedded entities which contain a empty collection of values that aren't entities are now considered empty, if this collection is empty.

Closes #1737
Original pull request: #1812

Author: schauder

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

@@ -422,7 +422,7 @@ public <T> T getPropertyValue(RelationalPersistentProperty property) {
 		@Override
 		public boolean hasValue(RelationalPersistentProperty property) {
 
-			if (property.isCollectionLike() || property.isMap()) {
+			if ((property.isCollectionLike() && property.isEntity())|| property.isMap()) {
 				// attempt relation fetch
 				return true;
 			}

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

@@ -55,6 +55,7 @@
 import org.springframework.data.mapping.context.InvalidPersistentPropertyPath;
 import org.springframework.data.relational.core.conversion.DbActionExecutionException;
 import org.springframework.data.relational.core.mapping.Column;
+import org.springframework.data.relational.core.mapping.Embedded;
 import org.springframework.data.relational.core.mapping.InsertOnlyProperty;
 import org.springframework.data.relational.core.mapping.MappedCollection;
 import org.springframework.data.relational.core.mapping.RelationalMappingContext;
@@ -772,6 +773,36 @@ void saveAndLoadAnEntityWithSet() {
 		assertThat(reloaded.digits).isEqualTo(new HashSet<>(asList("one", "two", "three")));
 	}
 
+	@Test //GH-1737
+	@EnabledOnFeature(SUPPORTS_ARRAYS)
+	void saveAndLoadEmbeddedArray() {
+
+		EmbeddedStringListOwner embeddedStringListOwner = new EmbeddedStringListOwner();
+		embeddedStringListOwner.embeddedStringList = new EmbeddedStringList();
+		embeddedStringListOwner.embeddedStringList.digits = List.of("one", "two", "three");
+
+		EmbeddedStringListOwner saved = template.save(embeddedStringListOwner);
+
+		EmbeddedStringListOwner reloaded = template.findById(saved.id, EmbeddedStringListOwner.class);
+
+		assertThat(reloaded.embeddedStringList.digits).containsExactly("one", "two", "three");
+	}
+
+	@Test //GH-1737
+	@EnabledOnFeature(SUPPORTS_ARRAYS)
+	void saveAndLoadEmptyEmbeddedArray() {
+
+		EmbeddedStringListOwner embeddedStringListOwner = new EmbeddedStringListOwner();
+		embeddedStringListOwner.embeddedStringList = new EmbeddedStringList();
+		embeddedStringListOwner.embeddedStringList.digits = emptyList();
+
+		EmbeddedStringListOwner saved = template.save(embeddedStringListOwner);
+
+		EmbeddedStringListOwner reloaded = template.findById(saved.id, EmbeddedStringListOwner.class);
+
+		assertThat(reloaded.embeddedStringList).isNull();
+	}
+
 	@Test
 	// DATAJDBC-327
 	void saveAndLoadAnEntityWithByteArray() {
@@ -1395,6 +1426,17 @@ private static class FloatListOwner {
 		List<Float> digits = new ArrayList<>();
 	}
 
+	@Table("ARRAY_OWNER")
+	private static class EmbeddedStringListOwner {
+		@Id Long id;
+
+		@Embedded(onEmpty = Embedded.OnEmpty.USE_NULL, prefix = "") EmbeddedStringList embeddedStringList;
+	}
+
+	private static class EmbeddedStringList {
+		List<String> digits = new ArrayList<>();
+	}
+
 	static class LegoSet {
 
 		@Column("id1")

spring-data-relational/src/main/java/org/springframework/data/relational/core/conversion/MappingRelationalConverter.java

@@ -44,16 +44,7 @@
 import org.springframework.data.mapping.PersistentPropertyAccessor;
 import org.springframework.data.mapping.PersistentPropertyPathAccessor;
 import org.springframework.data.mapping.context.MappingContext;
-import org.springframework.data.mapping.model.CachingValueExpressionEvaluatorFactory;
-import org.springframework.data.mapping.model.ConvertingPropertyAccessor;
-import org.springframework.data.mapping.model.EntityInstantiator;
-import org.springframework.data.mapping.model.ParameterValueProvider;
-import org.springframework.data.mapping.model.PersistentEntityParameterValueProvider;
-import org.springframework.data.mapping.model.PropertyValueProvider;
-import org.springframework.data.mapping.model.SimpleTypeHolder;
-import org.springframework.data.mapping.model.SpELContext;
-import org.springframework.data.mapping.model.ValueExpressionEvaluator;
-import org.springframework.data.mapping.model.ValueExpressionParameterValueProvider;
+import org.springframework.data.mapping.model.*;
 import org.springframework.data.projection.EntityProjection;
 import org.springframework.data.projection.EntityProjectionIntrospector;
 import org.springframework.data.projection.EntityProjectionIntrospector.ProjectionPredicate;
@@ -1168,7 +1159,43 @@ public Object getValue(AggregatePath path) {
 
 		@Override
 		public boolean hasValue(AggregatePath path) {
-			return document.get(path.getColumnInfo().alias().getReference()) != null;
+			Object value = document.get(path.getColumnInfo().alias().getReference());
+
+			if (value == null) {
+				return false;
+			}
+			if (!path.isCollectionLike()) {
+				return true;
+			}
+
+			if (value instanceof char[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof byte[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof short[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof int[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof long[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof float[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof double[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof Object[] ar) {
+				return ar.length != 0;
+			}
+			if (value instanceof Collection<?> col) {
+				return !col.isEmpty();
+			}
+			return true;
 		}
 
 		@Override