Migrate JDBC to use RowDocument for reading aggregates.

Original pull request #1618
See #1554

Author: mp911de

Diff for: spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/convert/BasicJdbcConverter.java

@@ -20,8 +20,10 @@
 import java.sql.ResultSet;
 import java.sql.SQLException;
 import java.sql.SQLType;
+import java.util.Iterator;
 import java.util.Map;
 import java.util.Optional;
+import java.util.function.Function;
 
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
@@ -44,13 +46,17 @@
 import org.springframework.data.mapping.model.SpELContext;
 import org.springframework.data.mapping.model.SpELExpressionEvaluator;
 import org.springframework.data.mapping.model.SpELExpressionParameterValueProvider;
+import org.springframework.data.projection.EntityProjection;
 import org.springframework.data.relational.core.conversion.MappingRelationalConverter;
+import org.springframework.data.relational.core.conversion.ObjectPath;
 import org.springframework.data.relational.core.conversion.RelationalConverter;
+import org.springframework.data.relational.core.conversion.RowDocumentAccessor;
 import org.springframework.data.relational.core.mapping.AggregatePath;
 import org.springframework.data.relational.core.mapping.RelationalMappingContext;
 import org.springframework.data.relational.core.mapping.RelationalPersistentEntity;
 import org.springframework.data.relational.core.mapping.RelationalPersistentProperty;
 import org.springframework.data.relational.core.sql.IdentifierProcessing;
+import org.springframework.data.relational.domain.RowDocument;
 import org.springframework.data.util.TypeInformation;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
@@ -83,18 +89,15 @@ public class BasicJdbcConverter extends MappingRelationalConverter implements Jd
 	private SpELContext spELContext;
 
 	/**
-	 * Creates a new {@link BasicJdbcConverter} given {@link MappingContext} and a
-	 * {@link JdbcTypeFactory#unsupported() no-op type factory} throwing {@link UnsupportedOperationException} on type
-	 * creation. Use
+	 * Creates a new {@link BasicJdbcConverter} given {@link MappingContext} and a {@link JdbcTypeFactory#unsupported()
+	 * no-op type factory} throwing {@link UnsupportedOperationException} on type creation. Use
 	 * {@link #BasicJdbcConverter(RelationalMappingContext, RelationResolver, CustomConversions, JdbcTypeFactory, IdentifierProcessing)}
 	 * (MappingContext, RelationResolver, JdbcTypeFactory)} to convert arrays and large objects into JDBC-specific types.
 	 *
 	 * @param context must not be {@literal null}.
 	 * @param relationResolver used to fetch additional relations from the database. Must not be {@literal null}.
 	 */
-	public BasicJdbcConverter(
-			RelationalMappingContext context,
-			RelationResolver relationResolver) {
+	public BasicJdbcConverter(RelationalMappingContext context, RelationResolver relationResolver) {
 
 		super(context, new JdbcCustomConversions());
 
@@ -115,10 +118,8 @@ public BasicJdbcConverter(
 	 * @param identifierProcessing must not be {@literal null}
 	 * @since 2.0
 	 */
-	public BasicJdbcConverter(
-			RelationalMappingContext context,
-			RelationResolver relationResolver, CustomConversions conversions, JdbcTypeFactory typeFactory,
-			IdentifierProcessing identifierProcessing) {
+	public BasicJdbcConverter(RelationalMappingContext context, RelationResolver relationResolver,
+			CustomConversions conversions, JdbcTypeFactory typeFactory, IdentifierProcessing identifierProcessing) {
 
 		super(context, conversions);
 
@@ -300,16 +301,241 @@ private JdbcValue tryToConvertToJdbcValue(@Nullable Object value) {
 
 	@Override
 	public <T> T mapRow(RelationalPersistentEntity<T> entity, ResultSet resultSet, Object key) {
-		return new ReadingContext<T>(getMappingContext().getAggregatePath( entity),
-				new ResultSetAccessor(resultSet), Identifier.empty(), key).mapRow();
+		return new ReadingContext<T>(getMappingContext().getAggregatePath(entity), new ResultSetAccessor(resultSet),
+				Identifier.empty(), key).mapRow();
 	}
 
-
 	@Override
 	public <T> T mapRow(AggregatePath path, ResultSet resultSet, Identifier identifier, Object key) {
 		return new ReadingContext<T>(path, new ResultSetAccessor(resultSet), identifier, key).mapRow();
 	}
 
+	@Override
+	public <R> R projectAndResolve(EntityProjection<R, ?> projection, RowDocument document) {
+
+		RelationalPersistentEntity<?> entity = getMappingContext()
+				.getRequiredPersistentEntity(projection.getActualDomainType());
+		ResolvingConversionContext context = new ResolvingConversionContext(newProjectingConversionContext(projection),
+				getMappingContext().getAggregatePath(entity), Identifier.empty());
+
+		return doReadProjection(context, document, projection);
+	}
+
+	@SuppressWarnings("unchecked")
+	@Override
+	public <R> R readAndResolve(Class<R> type, RowDocument source, Identifier identifier) {
+
+		RelationalPersistentEntity<R> entity = (RelationalPersistentEntity<R>) getMappingContext()
+				.getRequiredPersistentEntity(type);
+		AggregatePath path = getMappingContext().getAggregatePath(entity);
+		Identifier identifierToUse = ResolvingRelationalPropertyValueProvider.potentiallyAppendIdentifier(identifier,
+				entity, it -> source.get(it.getColumnName().getReference()));
+		ResolvingConversionContext context = new ResolvingConversionContext(getConversionContext(ObjectPath.ROOT), path,
+				identifierToUse);
+
+		return readAggregate(context, source, entity.getTypeInformation());
+	}
+
+	@Override
+	protected RelationalPropertyValueProvider newValueProvider(RowDocumentAccessor documentAccessor,
+			SpELExpressionEvaluator evaluator, ConversionContext context) {
+
+		if (context instanceof ResolvingConversionContext rcc) {
+
+			AggregatePathValueProvider delegate = (AggregatePathValueProvider) super.newValueProvider(documentAccessor,
+					evaluator, context);
+
+			return new ResolvingRelationalPropertyValueProvider(delegate, documentAccessor, rcc, rcc.identifier());
+		}
+
+		return super.newValueProvider(documentAccessor, evaluator, context);
+	}
+
+	/**
+	 * {@link RelationalPropertyValueProvider} using a resolving context to lookup relations. This is highly
+	 * context-sensitive. Note that the identifier is held here because of a chicken and egg problem, while
+	 * {@link ResolvingConversionContext} hols the {@link AggregatePath}.
+	 */
+	class ResolvingRelationalPropertyValueProvider implements RelationalPropertyValueProvider {
+
+		private final AggregatePathValueProvider delegate;
+
+		private final RowDocumentAccessor accessor;
+
+		private final ResolvingConversionContext context;
+
+		private final Identifier identifier;
+
+		private ResolvingRelationalPropertyValueProvider(AggregatePathValueProvider delegate, RowDocumentAccessor accessor,
+				ResolvingConversionContext context, Identifier identifier) {
+
+			AggregatePath path = context.aggregatePath();
+
+			this.delegate = delegate;
+			this.accessor = accessor;
+			this.context = context;
+			this.identifier = path.isEntity()
+					? potentiallyAppendIdentifier(identifier, path.getRequiredLeafEntity(), delegate::getPropertyValue)
+					: identifier;
+		}
+
+		/**
+		 * Conditionally append the identifier if the entity has an identifier property.
+		 */
+		static Identifier potentiallyAppendIdentifier(Identifier base, RelationalPersistentEntity<?> entity,
+				Function<RelationalPersistentProperty, Object> getter) {
+
+			if (entity.hasIdProperty()) {
+
+				RelationalPersistentProperty idProperty = entity.getRequiredIdProperty();
+				Object propertyValue = getter.apply(idProperty);
+
+				if (propertyValue != null) {
+					return base.withPart(idProperty.getColumnName(), propertyValue, idProperty.getType());
+				}
+			}
+
+			return base;
+		}
+
+		@SuppressWarnings("unchecked")
+		@Nullable
+		@Override
+		public <T> T getPropertyValue(RelationalPersistentProperty property) {
+
+			AggregatePath aggregatePath = this.context.aggregatePath();
+
+			if (getConversions().isSimpleType(property.getActualType())) {
+				return (T) delegate.getValue(aggregatePath);
+			}
+
+			if (property.isEntity()) {
+
+				if (property.isCollectionLike() || property.isMap()) {
+
+					Identifier identifier1 = this.identifier;
+					if (property.getOwner().hasIdProperty()) {
+						Object id = this.identifier.get(property.getOwner().getRequiredIdProperty().getColumnName());
+
+						if (id != null) {
+							identifier1 = Identifier.of(aggregatePath.getTableInfo().reverseColumnInfo().name(), id, Object.class);
+						}
+					}
+
+					Iterable<Object> allByPath = relationResolver.findAllByPath(identifier1,
+							aggregatePath.getRequiredPersistentPropertyPath());
+
+					if (property.isCollectionLike()) {
+						return (T) allByPath;
+					}
+
+					if (property.isMap()) {
+						return (T) ITERABLE_OF_ENTRY_TO_MAP_CONVERTER.convert(allByPath);
+					}
+
+					Iterator<Object> iterator = allByPath.iterator();
+					if (iterator.hasNext()) {
+						return (T) iterator.next();
+					}
+
+					return null;
+				}
+
+				return hasValue(property) ? (T) readAggregate(this.context, accessor, property.getTypeInformation()) : null;
+			}
+
+			return (T) delegate.getValue(aggregatePath);
+		}
+
+		@Override
+		public boolean hasValue(RelationalPersistentProperty property) {
+
+			if (property.isCollectionLike() || property.isMap()) {
+				// attempt relation fetch
+				return true;
+			}
+
+			AggregatePath aggregatePath = context.aggregatePath();
+
+			if (property.isEntity()) {
+
+				RelationalPersistentEntity<?> entity = getMappingContext().getRequiredPersistentEntity(property);
+				if (entity.hasIdProperty()) {
+
+					RelationalPersistentProperty referenceId = entity.getRequiredIdProperty();
+					AggregatePath toUse = aggregatePath.append(referenceId);
+					return delegate.hasValue(toUse);
+				}
+
+				return delegate.hasValue(aggregatePath.getTableInfo().reverseColumnInfo().alias());
+			}
+
+			return delegate.hasValue(aggregatePath);
+		}
+
+		@Override
+		public RelationalPropertyValueProvider withContext(ConversionContext context) {
+
+			return context == this.context ? this
+					: new ResolvingRelationalPropertyValueProvider(delegate.withContext(context), accessor,
+							(ResolvingConversionContext) context, identifier);
+		}
+
+	}
+
+	/**
+	 * Marker object to indicate that the property value provider should resolve relations.
+	 *
+	 * @param delegate
+	 * @param aggregatePath
+	 * @param identifier
+	 */
+	private record ResolvingConversionContext(ConversionContext delegate, AggregatePath aggregatePath,
+			Identifier identifier) implements ConversionContext {
+
+		@Override
+		public <S> 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) {
+			return delegate.convert(source, typeHint, context);
+		}
+
+		@Override
+		public ResolvingConversionContext forProperty(String name) {
+			RelationalPersistentProperty property = aggregatePath.getRequiredLeafEntity().getRequiredPersistentProperty(name);
+			return forProperty(property);
+		}
+
+		@Override
+		public ResolvingConversionContext forProperty(RelationalPersistentProperty property) {
+			ConversionContext nested = delegate.forProperty(property);
+			return new ResolvingConversionContext(nested, aggregatePath.append(property), identifier);
+		}
+
+		@Override
+		public ResolvingConversionContext withPath(ObjectPath currentPath) {
+			return new ResolvingConversionContext(delegate.withPath(currentPath), aggregatePath, identifier);
+		}
+
+		@Override
+		public ObjectPath getPath() {
+			return delegate.getPath();
+		}
+
+		@Override
+		public CustomConversions getCustomConversions() {
+			return delegate.getCustomConversions();
+		}
+
+		@Override
+		public RelationalConverter getSourceConverter() {
+			return delegate.getSourceConverter();
+		}
+	}
+
 	static Object[] requireObjectArray(Object source) {
 
 		Assert.isTrue(source.getClass().isArray(), "Source object is not an array");
@@ -361,25 +587,23 @@ private class ReadingContext<T> {
 		private final ResultSetAccessor accessor;
 
 		@SuppressWarnings("unchecked")
-		private ReadingContext(AggregatePath rootPath, ResultSetAccessor accessor, Identifier identifier,
-				Object key) {
+		private ReadingContext(AggregatePath rootPath, ResultSetAccessor accessor, Identifier identifier, Object key) {
 			RelationalPersistentEntity<T> entity = (RelationalPersistentEntity<T>) rootPath.getLeafEntity();
 
 			Assert.notNull(entity, "The rootPath must point to an entity");
 
 			this.entity = entity;
 			this.rootPath = rootPath;
-			this.path = getMappingContext().getAggregatePath( this.entity);
+			this.path = getMappingContext().getAggregatePath(this.entity);
 			this.identifier = identifier;
 			this.key = key;
 			this.propertyValueProvider = new JdbcPropertyValueProvider(path, accessor);
 			this.backReferencePropertyValueProvider = new JdbcBackReferencePropertyValueProvider(path, accessor);
 			this.accessor = accessor;
 		}
 
-		private ReadingContext(RelationalPersistentEntity<T> entity, AggregatePath rootPath,
-				AggregatePath path, Identifier identifier, Object key,
-				JdbcPropertyValueProvider propertyValueProvider,
+		private ReadingContext(RelationalPersistentEntity<T> entity, AggregatePath rootPath, AggregatePath path,
+				Identifier identifier, Object key, JdbcPropertyValueProvider propertyValueProvider,
 				JdbcBackReferencePropertyValueProvider backReferencePropertyValueProvider, ResultSetAccessor accessor) {
 
 			this.entity = entity;
@@ -396,8 +620,8 @@ private <S> ReadingContext<S> extendBy(RelationalPersistentProperty property) {
 
 			return new ReadingContext<>(
 					(RelationalPersistentEntity<S>) getMappingContext().getRequiredPersistentEntity(property.getActualType()),
-					rootPath.append(property), path.append(property), identifier, key,
-					propertyValueProvider.extendBy(property), backReferencePropertyValueProvider.extendBy(property), accessor);
+					rootPath.append(property), path.append(property), identifier, key, propertyValueProvider.extendBy(property),
+					backReferencePropertyValueProvider.extendBy(property), accessor);
 		}
 
 		T mapRow() {