Fix empty collection conversion.

We now consider the target type for empty collections.

Closes #796

Author: mp911de

src/main/java/org/springframework/data/r2dbc/convert/MappingR2dbcConverter.java

@@ -190,7 +190,6 @@ private Object readFrom(Row row, @Nullable RowMetadata metadata, RelationalPersi
 		}
 	}
 
-
 	public Object readValue(@Nullable Object value, TypeInformation<?> type) {
 
 		if (null == value) {
@@ -553,6 +552,8 @@ public Object getArrayValue(ArrayColumns arrayColumns, RelationalPersistentPrope
 			actualType = property.getActualType();
 		}
 
+		actualType = getTargetType(actualType);
+
 		Class<?> targetType = arrayColumns.getArrayType(actualType);
 
 		if (!property.isArray() || !targetType.isAssignableFrom(value.getClass())) {

src/main/java/org/springframework/data/r2dbc/core/DefaultReactiveDataAccessStrategy.java

@@ -240,7 +240,6 @@ private Parameter getArrayValue(Parameter value, RelationalPersistentProperty pr
 		ArrayColumns arrayColumns = this.dialect.getArraySupport();
 
 		if (!arrayColumns.isSupported()) {
-
 			throw new InvalidDataAccessResourceUsageException(
 					"Dialect " + this.dialect.getClass().getName() + " does not support array columns");
 		}
@@ -266,8 +265,7 @@ private Parameter getArrayValue(Parameter value, RelationalPersistentProperty pr
 			return Parameter.empty(targetArrayType);
 		}
 
-		return Parameter.fromOrEmpty(this.converter.getArrayValue(arrayColumns, property, value.getValue()),
-				actualType);
+		return Parameter.fromOrEmpty(this.converter.getArrayValue(arrayColumns, property, value.getValue()), actualType);
 	}
 
 	/*

src/test/java/org/springframework/data/r2dbc/core/PostgresReactiveDataAccessStrategyTests.java

@@ -17,8 +17,11 @@
 
 import static org.springframework.data.r2dbc.testing.Assertions.*;
 
+import io.r2dbc.postgresql.codec.Interval;
 import lombok.RequiredArgsConstructor;
 
+import java.time.Duration;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.EnumSet;
@@ -28,6 +31,7 @@
 import org.junit.jupiter.api.Test;
 
 import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.convert.ReadingConverter;
 import org.springframework.data.convert.WritingConverter;
 import org.springframework.data.r2dbc.convert.EnumWriteSupport;
 import org.springframework.data.r2dbc.dialect.PostgresDialect;
@@ -41,7 +45,8 @@
  */
 public class PostgresReactiveDataAccessStrategyTests extends ReactiveDataAccessStrategyTestSupport {
 
-	private final ReactiveDataAccessStrategy strategy = new DefaultReactiveDataAccessStrategy(PostgresDialect.INSTANCE);
+	private final ReactiveDataAccessStrategy strategy = new DefaultReactiveDataAccessStrategy(PostgresDialect.INSTANCE,
+			Arrays.asList(DurationToIntervalConverter.INSTANCE, IntervalToDurationConverter.INSTANCE));
 
 	@Override
 	protected ReactiveDataAccessStrategy getStrategy() {
@@ -116,6 +121,17 @@ void shouldApplyCustomConversionForNull() {
 		assertThat(outboundRow).containsColumn("my_objects").withColumn("my_objects").isEmpty().hasType(String.class);
 	}
 
+	@Test // gh-796
+	void shouldApplyCustomConversionForEmptyList() {
+
+		WithDuration withDuration = new WithDuration();
+		withDuration.durations = new ArrayList<>();
+
+		OutboundRow outboundRow = strategy.getOutboundRow(withDuration);
+
+		assertThat(outboundRow).containsColumn("durations").withColumn("durations").hasType(Interval[].class);
+	}
+
 	@Test // gh-252, gh-593
 	void shouldConvertCollectionOfEnumToString() {
 
@@ -202,6 +218,11 @@ static class WithArray {
 		List<String> stringList;
 	}
 
+	static class WithDuration {
+
+		List<Duration> durations;
+	}
+
 	static class WithEnumCollections {
 
 		MyEnum[] enumArray;
@@ -242,5 +263,27 @@ public String convert(List<MyObject> myObjects) {
 		}
 	}
 
+	@WritingConverter
+	enum DurationToIntervalConverter implements Converter<Duration, Interval> {
+
+		INSTANCE;
+
+		@Override
+		public Interval convert(Duration duration) {
+			return Interval.of(duration);
+		}
+	}
+
+	@ReadingConverter
+	enum IntervalToDurationConverter implements Converter<Interval, Duration> {
+
+		INSTANCE;
+
+		@Override
+		public Duration convert(Interval interval) {
+			return interval.getDuration();
+		}
+	}
+
 	private static class MyEnumSupport extends EnumWriteSupport<MyEnum> {}
 }