Polishing.

Fix nullability issues.

See #2217

(cherry picked from commit 08c86dc94e)

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

@@ -19,7 +19,6 @@ import java.util.HashMap;
 import java.util.Map;
 import java.util.Map.Entry;
 
-import org.jspecify.annotations.Nullable;
 import org.springframework.core.convert.TypeDescriptor;
 import org.springframework.core.convert.converter.ConditionalConverter;
 import org.springframework.core.convert.converter.Converter;
@@ -32,16 +31,14 @@ import org.springframework.util.Assert;
  */
 class IterableOfEntryToMapConverter implements ConditionalConverter, Converter<Iterable<?>, Map<?, ?>> {
 
-	@SuppressWarnings("unchecked")
-	@Nullable
 	@Override
 	public Map<?, ?> convert(Iterable<?> source) {
 
-		Map result = new HashMap();
+		Map<Object, Object> result = new HashMap<>();
 
 		source.forEach(element -> {
 
-			if (element instanceof Entry entry) {
+			if (element instanceof Entry<?, ?> entry) {
 				result.put(entry.getKey(), entry.getValue());
 				return;
 			}

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

@@ -200,8 +200,7 @@ public class MappingJdbcConverter extends MappingRelationalConverter implements
 	 * @return
 	 */
 	@Override
-	@Nullable
-	public Object readValue(@Nullable Object value, TypeInformation<?> targetType) {
+	public @Nullable Object readValue(@Nullable Object value, TypeInformation<?> targetType) {
 
 		if (null == value) {
 			return null;
@@ -573,12 +572,12 @@ public class MappingJdbcConverter extends MappingRelationalConverter implements
 			Identifier identifier) implements ConversionContext {
 
 		@Override
-		public <S> S convert(Object source, TypeInformation<? extends S> typeHint) {
+		public <S> @Nullable S convert(Object source, TypeInformation<? extends S> typeHint) {
 			return delegate.convert(source, typeHint);
 		}
 
 		@Override
-		public <S> S convert(Object source, TypeInformation<? extends S> typeHint, ConversionContext context) {
+		public <S> @Nullable S convert(Object source, TypeInformation<? extends S> typeHint, ConversionContext context) {
 			return delegate.convert(source, typeHint, context);
 		}
 

spring-data-r2dbc/src/main/java/org/springframework/data/r2dbc/convert/R2dbcConverters.java

@@ -70,12 +70,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToBooleanConverter implements Converter<Row, Boolean> {
+	public enum RowToBooleanConverter implements Converter<Row, @Nullable Boolean> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable Boolean convert(Row row) {
+		public Boolean convert(Row row) {
 			return row.get(0, Boolean.class);
 		}
 	}
@@ -85,12 +85,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToLocalDateConverter implements Converter<Row, LocalDate> {
+	public enum RowToLocalDateConverter implements Converter<Row, @Nullable LocalDate> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable LocalDate convert(Row row) {
+		public LocalDate convert(Row row) {
 			return row.get(0, LocalDate.class);
 		}
 	}
@@ -100,12 +100,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToLocalDateTimeConverter implements Converter<Row, LocalDateTime> {
+	public enum RowToLocalDateTimeConverter implements Converter<Row, @Nullable LocalDateTime> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable LocalDateTime convert(Row row) {
+		public LocalDateTime convert(Row row) {
 			return row.get(0, LocalDateTime.class);
 		}
 	}
@@ -115,12 +115,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToLocalTimeConverter implements Converter<Row, LocalTime> {
+	public enum RowToLocalTimeConverter implements Converter<Row, @Nullable LocalTime> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable LocalTime convert(Row row) {
+		public LocalTime convert(Row row) {
 			return row.get(0, LocalTime.class);
 		}
 	}
@@ -141,20 +141,21 @@ abstract class R2dbcConverters {
 	 * @see java.math.BigDecimal
 	 * @author Hebert Coelho
 	 */
-	public enum RowToNumberConverterFactory implements ConverterFactory<Row, Number> {
+	public enum RowToNumberConverterFactory implements ConverterFactory<Row, @Nullable Number> {
 
 		INSTANCE;
 
 		@Override
-		public <T extends Number> Converter<Row, T> getConverter(Class<T> targetType) {
+		public <T extends @Nullable Number> Converter<Row, T> getConverter(Class<T> targetType) {
 			Assert.notNull(targetType, "Target type must not be null");
 			return new RowToNumber<>(targetType);
 		}
 
-		record RowToNumber<T extends Number>(Class<T> targetType) implements Converter<Row, T> {
+		@SuppressWarnings("NullAway")
+		record RowToNumber<T extends @Nullable Number>(Class<T> targetType) implements Converter<Row, @Nullable T> {
 
 			@Override
-			public @Nullable T convert(Row source) {
+			public T convert(Row source) {
 
 				Object object = source.get(0);
 
@@ -168,12 +169,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToOffsetDateTimeConverter implements Converter<Row, OffsetDateTime> {
+	public enum RowToOffsetDateTimeConverter implements Converter<Row, @Nullable OffsetDateTime> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable OffsetDateTime convert(Row row) {
+		public OffsetDateTime convert(Row row) {
 			return row.get(0, OffsetDateTime.class);
 		}
 	}
@@ -183,12 +184,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToStringConverter implements Converter<Row, String> {
+	public enum RowToStringConverter implements Converter<Row, @Nullable String> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable String convert(Row row) {
+		public String convert(Row row) {
 			return row.get(0, String.class);
 		}
 	}
@@ -198,12 +199,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToUuidConverter implements Converter<Row, UUID> {
+	public enum RowToUuidConverter implements Converter<Row, @Nullable UUID> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable UUID convert(Row row) {
+		public UUID convert(Row row) {
 			return row.get(0, UUID.class);
 		}
 	}
@@ -213,12 +214,12 @@ abstract class R2dbcConverters {
 	 *
 	 * @author Hebert Coelho
 	 */
-	public enum RowToZonedDateTimeConverter implements Converter<Row, ZonedDateTime> {
+	public enum RowToZonedDateTimeConverter implements Converter<Row, @Nullable ZonedDateTime> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable ZonedDateTime convert(Row row) {
+		public ZonedDateTime convert(Row row) {
 			return row.get(0, ZonedDateTime.class);
 		}
 	}

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

@@ -80,12 +80,13 @@ public class MySqlDialect extends org.springframework.data.relational.core.diale
 	 * @author Michael Berry
 	 */
 	@ReadingConverter
-	public enum ByteToBooleanConverter implements Converter<Byte, Boolean> {
+	@SuppressWarnings("NullAway")
+	public enum ByteToBooleanConverter implements Converter<Byte, @Nullable Boolean> {
 
 		INSTANCE;
 
 		@Override
-		public @Nullable Boolean convert(@Nullable Byte s) {
+		public Boolean convert(@Nullable Byte s) {
 
 			if (s == null) {
 				return null;

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

@@ -352,9 +352,7 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 		if (getConversions().hasCustomReadTarget(RowDocument.class, rawType)) {
 
 			S converted = doConvert(documentAccessor.getDocument(), rawType, typeHint.getType());
-
 			Assert.state(converted != null, "Converted must not be null");
-
 			return converted;
 		}
 
@@ -363,7 +361,10 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 		}
 
 		if (typeHint.isMap()) {
-			return context.convert(documentAccessor, typeHint);
+
+			S converted = context.convert(documentAccessor, typeHint);
+			Assert.state(converted != null, "Converted must not be null");
+			return converted;
 		}
 
 		RelationalPersistentEntity<?> entity = getMappingContext().getPersistentEntity(typeHint);
@@ -425,7 +426,7 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 	 * @param targetType the {@link Map} {@link TypeInformation} to be used to unmarshall this {@link RowDocument}.
 	 * @return the converted {@link Collection} or array, will never be {@literal null}.
 	 */
-	protected @Nullable Object readCollectionOrArray(ConversionContext context, Collection<?> source,
+	protected Object readCollectionOrArray(ConversionContext context, Collection<?> source,
 			TypeInformation<?> targetType) {
 
 		Assert.notNull(targetType, "Target type must not be null");
@@ -444,14 +445,14 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 				: CollectionFactory.createCollection(collectionType, rawComponentType, source.size());
 
 		if (source.isEmpty()) {
-			return getPotentiallyConvertedSimpleRead(items, targetType);
+			return getRequiredPotentiallyConvertedSimpleRead(items, targetType);
 		}
 
 		for (Object element : source) {
 			items.add(element != null ? context.convert(element, componentType) : element);
 		}
 
-		return getPotentiallyConvertedSimpleRead(items, targetType);
+		return getRequiredPotentiallyConvertedSimpleRead(items, targetType);
 	}
 
 	private <T> @Nullable T doConvert(Object value, Class<? extends T> target) {
@@ -637,17 +638,17 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 	 *
 	 * @param value a value as it is returned by the driver accessing the persistence store. May be {@literal null}.
 	 * @param targetType {@link TypeInformation} into which the value is to be converted. Must not be {@literal null}.
-	 * @return The converted value. May be {@literal null}.
+	 * @return the converted value, can be {@literal null}.
 	 */
 	@Override
-	@Nullable
-	public Object readValue(@Nullable Object value, TypeInformation<?> targetType) {
-
-		if (null == value) {
-			return null;
-		}
+	public @Nullable Object readValue(@Nullable Object value, TypeInformation<?> targetType) {
+		return null == value ? null : getPotentiallyConvertedSimpleRead(value, targetType);
+	}
 
-		return getPotentiallyConvertedSimpleRead(value, targetType);
+	private Object getRequiredPotentiallyConvertedSimpleRead(Object value, TypeInformation<?> type) {
+		Object result = getPotentiallyConvertedSimpleRead(value, type);
+		Assert.state(result != null, "Converted must not be null");
+		return result;
 	}
 
 	/**
@@ -865,7 +866,7 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 
 		@SuppressWarnings("unchecked")
 		@Override
-		public <S> S convert(Object source, TypeInformation<? extends S> typeHint, ConversionContext context) {
+		public <S> @Nullable S convert(Object source, TypeInformation<? extends S> typeHint, ConversionContext context) {
 
 			Assert.notNull(source, "Source must not be null");
 			Assert.notNull(typeHint, "TypeInformation must not be null");
@@ -875,7 +876,6 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 			}
 
 			if (source instanceof Collection<?> collection) {
-
 				if (typeHint.isCollectionLike() || typeHint.getType().isAssignableFrom(Collection.class)) {
 					return (S) collectionConverter.convert(context, collection, typeHint);
 				}
@@ -1011,9 +1011,9 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 		 *
 		 * @param source must not be {@literal null}.
 		 * @param typeHint must not be {@literal null}.
-		 * @return the converted object.
+		 * @return the converted object, can be {@literal null}.
 		 */
-		default <S> S convert(Object source, TypeInformation<? extends S> typeHint) {
+		default <S> @Nullable S convert(Object source, TypeInformation<? extends S> typeHint) {
 			return convert(source, typeHint, this);
 		}
 
@@ -1023,9 +1023,9 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 		 * @param source must not be {@literal null}.
 		 * @param typeHint must not be {@literal null}.
 		 * @param context must not be {@literal null}.
-		 * @return the converted object.
+		 * @return the converted object, can be {@literal null}.
 		 */
-		<S> S convert(Object source, TypeInformation<? extends S> typeHint, ConversionContext context);
+		<S> @Nullable S convert(Object source, TypeInformation<? extends S> typeHint, ConversionContext context);
 
 		/**
 		 * Obtain a {@link ConversionContext} for the given property {@code name}.
@@ -1186,9 +1186,8 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 		}
 
 		@Override
-		@Nullable
 		@SuppressWarnings("unchecked")
-		public <T> T getPropertyValue(RelationalPersistentProperty property) {
+		public <T> @Nullable T getPropertyValue(RelationalPersistentProperty property) {
 
 			String expression = property.getSpelExpression();
 			Object value = expression != null ? evaluator.evaluate(expression) : accessor.get(property);
@@ -1353,7 +1352,7 @@ public class MappingRelationalConverter extends AbstractRelationalConverter
 		}
 
 		@Override
-		protected <T> T potentiallyConvertExpressionValue(Object object,
+		protected <T> @Nullable T potentiallyConvertExpressionValue(Object object,
 				Parameter<T, RelationalPersistentProperty> parameter) {
 			return context.convert(object, parameter.getType());
 		}

spring-data-relational/src/main/java/org/springframework/data/relational/core/sql/render/TypedSubtreeVisitor.java

@@ -15,6 +15,7 @@
  */
 package org.springframework.data.relational.core.sql.render;
 
+import java.util.Objects;
 import java.util.function.Predicate;
 
 import org.jspecify.annotations.Nullable;
@@ -50,23 +51,19 @@ abstract class TypedSubtreeVisitor<T extends Visitable> extends DelegatingVisito
 	private final ResolvableType type;
 	private @Nullable Visitable currentSegment;
 
-	enum Assignable {
-		YES, NO,
-	}
-
 	/**
 	 * Creates a new {@link TypedSubtreeVisitor}.
 	 */
 	TypedSubtreeVisitor() {
-		this.type = refCache.computeIfAbsent(this.getClass(),
-				key -> ResolvableType.forClass(key).as(TypedSubtreeVisitor.class).getGeneric(0));
+		this.type = Objects.requireNonNull(refCache.computeIfAbsent(this.getClass(),
+				key -> ResolvableType.forClass(key).as(TypedSubtreeVisitor.class).getGeneric(0)));
 	}
 
 	/**
 	 * Creates a new {@link TypedSubtreeVisitor} with an explicitly provided type.
 	 */
 	TypedSubtreeVisitor(Class<T> type) {
-		this.type = refCache.computeIfAbsent(type, key -> ResolvableType.forClass(type));
+		this.type = Objects.requireNonNull(refCache.computeIfAbsent(type, key -> ResolvableType.forClass(type)));
 	}
 
 	/**