Support AggregateReferences with custom id type.

Restructured reading conversion process into:
- converting technology base types (JDBC Arrays).
- standard and custom conversions.
- module specific conversions (AggregateReference).

Closes #1828
Original pull request #2062

Author: schauder

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

@@ -27,9 +27,7 @@
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
 import org.springframework.context.ApplicationContextAware;
-import org.springframework.core.convert.ConverterNotFoundException;
 import org.springframework.core.convert.converter.Converter;
-import org.springframework.core.convert.converter.ConverterRegistry;
 import org.springframework.data.convert.CustomConversions;
 import org.springframework.data.jdbc.core.mapping.AggregateReference;
 import org.springframework.data.jdbc.core.mapping.JdbcValue;
@@ -91,8 +89,6 @@ public MappingJdbcConverter(RelationalMappingContext context, RelationResolver r
 
 		this.typeFactory = JdbcTypeFactory.unsupported();
 		this.relationResolver = relationResolver;
-
-		registerAggregateReferenceConverters();
 	}
 
 	/**
@@ -112,14 +108,6 @@ public MappingJdbcConverter(RelationalMappingContext context, RelationResolver r
 
 		this.typeFactory = typeFactory;
 		this.relationResolver = relationResolver;
-
-		registerAggregateReferenceConverters();
-	}
-
-	private void registerAggregateReferenceConverters() {
-
-		ConverterRegistry registry = (ConverterRegistry) getConversionService();
-		AggregateReferenceConverters.getConvertersToRegister(getConversionService()).forEach(registry::addConverter);
 	}
 
 	@Nullable
@@ -185,33 +173,48 @@ private Class<?> doGetColumnType(RelationalPersistentProperty property) {
 	}
 
 	@Override
-	@Nullable
-	public Object readValue(@Nullable Object value, TypeInformation<?> type) {
-
-		if (value == null) {
-			return value;
-		}
+	protected Object readTechnologyType(Object value) {
 
 		if (value instanceof Array array) {
 			try {
-				return super.readValue(array.getArray(), type);
-			} catch (SQLException | ConverterNotFoundException e) {
+				return array.getArray();
+			} catch (SQLException e) {
 				LOG.info("Failed to extract a value of type %s from an Array; Attempting to use standard conversions", e);
+
 			}
 		}
 
-		return super.readValue(value, type);
+		return value;
 	}
 
 	@Override
+	protected TypeInformation<?> determineModuleReadTarget(TypeInformation<?> ultimateTargetType) {
+
+		if (AggregateReference.class.isAssignableFrom(ultimateTargetType.getType())) {
+			// the id type of a AggregateReference
+			return ultimateTargetType.getTypeArguments().get(1);
+		}
+		return ultimateTargetType;
+	}
+
+	@Override
+	protected Object readModuleType(Object value, TypeInformation<?> targetType) {
+
+		if (AggregateReference.class.isAssignableFrom(targetType.getType())) {
+			return AggregateReference.to(value);
+		}
+		return value;
+	}
+
 	@Nullable
-	public Object writeValue(@Nullable Object value, TypeInformation<?> type) {
+	@Override
+	protected Object getPotentiallyConvertedSimpleWrite(Object value, TypeInformation<?> type) {
 
-		if (value == null) {
-			return null;
+		if (value instanceof AggregateReference<?, ?> aggregateReference) {
+			return writeValue(aggregateReference.getId(), type);
 		}
 
-		return super.writeValue(value, type);
+		return super.getPotentiallyConvertedSimpleWrite(value, type);
 	}
 
 	private boolean canWriteAsJdbcValue(@Nullable Object value) {

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/convert/BasicRelationalConverterAggregateReferenceUnitTests.java renamed to spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/convert/MappingJdbcConverterAggregateReferenceUnitTests.java

@@ -32,15 +32,15 @@
  *
  * @author Jens Schauder
  */
-public class BasicRelationalConverterAggregateReferenceUnitTests {
+class MappingJdbcConverterAggregateReferenceUnitTests {
 
 	JdbcMappingContext context = new JdbcMappingContext();
 	JdbcConverter converter = new MappingJdbcConverter(context, mock(RelationResolver.class));
 
 	RelationalPersistentEntity<?> entity = context.getRequiredPersistentEntity(DummyEntity.class);
 
 	@Test // DATAJDBC-221
-	public void convertsToAggregateReference() {
+	void convertsToAggregateReference() {
 
 		final RelationalPersistentProperty property = entity.getRequiredPersistentProperty("reference");
 
@@ -51,7 +51,7 @@ public void convertsToAggregateReference() {
 	}
 
 	@Test // DATAJDBC-221
-	public void convertsFromAggregateReference() {
+	void convertsFromAggregateReference() {
 
 		final RelationalPersistentProperty property = entity.getRequiredPersistentProperty("reference");
 

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

@@ -40,6 +40,7 @@
 import org.junit.jupiter.api.Test;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.annotation.Id;
+import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.jdbc.core.mapping.AggregateReference;
 import org.springframework.data.jdbc.core.mapping.JdbcMappingContext;
 import org.springframework.data.jdbc.core.mapping.JdbcValue;
@@ -60,8 +61,7 @@ class MappingJdbcConverterUnitTests {
 
 	private static final UUID UUID = java.util.UUID.fromString("87a48aa8-a071-705e-54a9-e52fe3a012f1");
 	private static final byte[] BYTES_REPRESENTING_UUID = { -121, -92, -118, -88, -96, 113, 112, 94, 84, -87, -27, 47,
-			-29,
-			-96, 18, -15 };
+			-29, -96, 18, -15 };
 
 	private JdbcMappingContext context = new JdbcMappingContext();
 	private StubbedJdbcTypeFactory typeFactory = new StubbedJdbcTypeFactory();
@@ -70,7 +70,7 @@ class MappingJdbcConverterUnitTests {
 			(identifier, path) -> {
 				throw new UnsupportedOperationException();
 			}, //
-			new JdbcCustomConversions(), //
+			new JdbcCustomConversions(List.of(CustomIdToLong.INSTANCE)), //
 			typeFactory //
 	);
 
@@ -91,6 +91,7 @@ void testTargetTypesForPropertyType() {
 		checkTargetType(softly, entity, "date", Date.class);
 		checkTargetType(softly, entity, "timestamp", Timestamp.class);
 		checkTargetType(softly, entity, "uuid", UUID.class);
+		checkTargetType(softly, entity, "reference", Long.class);
 
 		softly.assertAll();
 	}
@@ -216,117 +217,26 @@ private void checkTargetType(SoftAssertions softly, RelationalPersistentEntity<?
 	}
 
 	@SuppressWarnings("unused")
-	private static class DummyEntity {
-
-		@Id private final Long id;
-		private final SomeEnum someEnum;
-		private final LocalDateTime localDateTime;
-		private final LocalDate localDate;
-		private final LocalTime localTime;
-		private final ZonedDateTime zonedDateTime;
-		private final OffsetDateTime offsetDateTime;
-		private final Instant instant;
-		private final Date date;
-		private final Timestamp timestamp;
-		private final AggregateReference<DummyEntity, Long> reference;
-		private final UUID uuid;
-		private final AggregateReference<ReferencedByUuid, UUID> uuidRef;
-		private final Optional<UUID> optionalUuid;
-
-		// DATAJDBC-259
-		private final List<String> listOfString;
-		private final String[] arrayOfString;
-		private final List<OtherEntity> listOfEntity;
-		private final OtherEntity[] arrayOfEntity;
-
-		private DummyEntity(Long id, SomeEnum someEnum, LocalDateTime localDateTime, LocalDate localDate,
-							LocalTime localTime, ZonedDateTime zonedDateTime, OffsetDateTime offsetDateTime, Instant instant, Date date,
-							Timestamp timestamp, AggregateReference<DummyEntity, Long> reference, UUID uuid,
-							AggregateReference<ReferencedByUuid, UUID> uuidRef, Optional<java.util.UUID> optionalUUID, List<String> listOfString, String[] arrayOfString,
-							List<OtherEntity> listOfEntity, OtherEntity[] arrayOfEntity) {
-			this.id = id;
-			this.someEnum = someEnum;
-			this.localDateTime = localDateTime;
-			this.localDate = localDate;
-			this.localTime = localTime;
-			this.zonedDateTime = zonedDateTime;
-			this.offsetDateTime = offsetDateTime;
-			this.instant = instant;
-			this.date = date;
-			this.timestamp = timestamp;
-			this.reference = reference;
-			this.uuid = uuid;
-			this.uuidRef = uuidRef;
-			this.optionalUuid = optionalUUID;
-			this.listOfString = listOfString;
-			this.arrayOfString = arrayOfString;
-			this.listOfEntity = listOfEntity;
-			this.arrayOfEntity = arrayOfEntity;
-		}
-
-		public Long getId() {
-			return this.id;
-		}
-
-		public SomeEnum getSomeEnum() {
-			return this.someEnum;
-		}
-
-		public LocalDateTime getLocalDateTime() {
-			return this.localDateTime;
-		}
-
-		public LocalDate getLocalDate() {
-			return this.localDate;
-		}
-
-		public LocalTime getLocalTime() {
-			return this.localTime;
-		}
-
-		public ZonedDateTime getZonedDateTime() {
-			return this.zonedDateTime;
-		}
-
-		public OffsetDateTime getOffsetDateTime() {
-			return this.offsetDateTime;
-		}
-
-		public Instant getInstant() {
-			return this.instant;
-		}
-
-		public Date getDate() {
-			return this.date;
-		}
-
-		public Timestamp getTimestamp() {
-			return this.timestamp;
-		}
-
-		public AggregateReference<DummyEntity, Long> getReference() {
-			return this.reference;
-		}
-
-		public UUID getUuid() {
-			return this.uuid;
-		}
-
-		public List<String> getListOfString() {
-			return this.listOfString;
-		}
-
-		public String[] getArrayOfString() {
-			return this.arrayOfString;
-		}
-
-		public List<OtherEntity> getListOfEntity() {
-			return this.listOfEntity;
-		}
-
-		public OtherEntity[] getArrayOfEntity() {
-			return this.arrayOfEntity;
-		}
+	private record DummyEntity( //
+			@Id Long id, //
+			SomeEnum someEnum, //
+			LocalDateTime localDateTime, //
+			LocalDate localDate, //
+			LocalTime localTime, //
+			ZonedDateTime zonedDateTime, //
+			OffsetDateTime offsetDateTime, //
+			Instant instant, //
+			Date date, //
+			Timestamp timestamp, //
+			AggregateReference<DummyEntity, Long> reference, //
+			UUID uuid, //
+			AggregateReference<ReferencedByUuid, UUID> uuidRef, //
+			Optional<UUID> optionalUuid, //
+			List<String> listOfString, //
+			String[] arrayOfString, //
+			List<OtherEntity> listOfEntity, //
+			OtherEntity[] arrayOfEntity //
+	) {
 	}
 
 	@SuppressWarnings("unused")
@@ -337,6 +247,18 @@ private enum SomeEnum {
 	@SuppressWarnings("unused")
 	private static class OtherEntity {}
 
+	private static class EnumIdEntity {
+		@Id SomeEnum id;
+	}
+
+	private static class CustomIdEntity {
+		@Id CustomId id;
+	}
+
+	private record CustomId(Long id) {
+
+	}
+
 	private static class StubbedJdbcTypeFactory implements JdbcTypeFactory {
 		Object[] arraySource;
 
@@ -366,4 +288,14 @@ public UUID convert(byte[] source) {
 			return new UUID(high, low);
 		}
 	}
+
+	@WritingConverter
+	enum CustomIdToLong implements Converter<CustomId, Long> {
+		INSTANCE;
+
+		@Override
+		public Long convert(CustomId source) {
+			return source.id;
+		}
+	}
 }