#69 - Allow object creation with a subset of columns.

We now allow object creation when not all columns are present by leveraging R2DBC RowMetadata. A column subset is necessary for projections.

Author: mp911de

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

@@ -43,6 +43,6 @@ public EntityRowMapper(Class<T> typeRoRead, R2dbcConverter converter) {
 	 */
 	@Override
 	public T apply(Row row, RowMetadata metadata) {
-		return converter.read(typeRoRead, row);
+		return converter.read(typeRoRead, row, metadata);
 	}
 }

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

@@ -84,8 +84,21 @@ public MappingR2dbcConverter(
 	// Entity reading
 	// ----------------------------------
 
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.convert.EntityReader#read(java.lang.Class, S)
+	 */
 	@Override
 	public <R> R read(Class<R> type, Row row) {
+		return read(type, row, null);
+	}
+
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.r2dbc.convert.R2dbcConverter#read(java.lang.Class, io.r2dbc.spi.Row, io.r2dbc.spi.RowMetadata)
+	 */
+	@Override
+	public <R> R read(Class<R> type, Row row, @Nullable RowMetadata metadata) {
 
 		TypeInformation<? extends R> typeInfo = ClassTypeInformation.from(type);
 		Class<? extends R> rawType = typeInfo.getType();
@@ -99,10 +112,10 @@ public <R> R read(Class<R> type, Row row) {
 			return getConversionService().convert(row, rawType);
 		}
 
-		return read(getRequiredPersistentEntity(type), row);
+		return read(getRequiredPersistentEntity(type), row, metadata);
 	}
 
-	private <R> R read(RelationalPersistentEntity<R> entity, Row row) {
+	private <R> R read(RelationalPersistentEntity<R> entity, Row row, @Nullable RowMetadata metadata) {
 
 		R result = createInstance(row, "", entity);
 
@@ -115,7 +128,7 @@ private <R> R read(RelationalPersistentEntity<R> entity, Row row) {
 				continue;
 			}
 
-			Object value = readFrom(row, property, "");
+			Object value = readFrom(row, metadata, property, "");
 
 			if (value != null) {
 				propertyAccessor.setProperty(property, value);
@@ -129,20 +142,27 @@ private <R> R read(RelationalPersistentEntity<R> entity, Row row) {
 	 * Read a single value or a complete Entity from the {@link Row} passed as an argument.
 	 *
 	 * @param row the {@link Row} to extract the value from. Must not be {@literal null}.
+	 * @param metadata the {@link RowMetadata}. Can be {@literal null}.
 	 * @param property the {@link RelationalPersistentProperty} for which the value is intended. Must not be
 	 *          {@literal null}.
 	 * @param prefix to be used for all column names accessed by this method. Must not be {@literal null}.
 	 * @return the value read from the {@link Row}. May be {@literal null}.
 	 */
-	private Object readFrom(Row row, RelationalPersistentProperty property, String prefix) {
+	private Object readFrom(Row row, @Nullable RowMetadata metadata, RelationalPersistentProperty property,
+			String prefix) {
 
 		try {
 
 			if (property.isEntity()) {
-				return readEntityFrom(row, property);
+				return readEntityFrom(row, metadata, property);
 			}
 
-			Object value = row.get(prefix + property.getColumnName());
+			String identifier = prefix + property.getColumnName();
+			if (metadata != null && !metadata.getColumnNames().contains(identifier)) {
+				return null;
+			}
+
+			Object value = row.get(identifier);
 			return getPotentiallyConvertedSimpleRead(value, property.getTypeInformation().getType());
 
 		} catch (Exception o_O) {
@@ -178,13 +198,13 @@ private Object getPotentiallyConvertedSimpleRead(@Nullable Object value, @Nullab
 	}
 
 	@SuppressWarnings("unchecked")
-	private <S> S readEntityFrom(Row row, PersistentProperty<?> property) {
+	private <S> S readEntityFrom(Row row, RowMetadata metadata, PersistentProperty<?> property) {
 
 		String prefix = property.getName() + "_";
 
 		RelationalPersistentEntity<?> entity = getMappingContext().getRequiredPersistentEntity(property.getActualType());
 
-		if (readFrom(row, entity.getRequiredIdProperty(), prefix) == null) {
+		if (readFrom(row, metadata, entity.getRequiredIdProperty(), prefix) == null) {
 			return null;
 		}
 
@@ -195,7 +215,7 @@ private <S> S readEntityFrom(Row row, PersistentProperty<?> property) {
 
 		for (RelationalPersistentProperty p : entity) {
 			if (!entity.isConstructorArgument(property)) {
-				propertyAccessor.setProperty(p, readFrom(row, p, prefix));
+				propertyAccessor.setProperty(p, readFrom(row, metadata, p, prefix));
 			}
 		}
 
@@ -213,6 +233,10 @@ private <S> S createInstance(Row row, String prefix, RelationalPersistentEntity<
 	// Entity writing
 	// ----------------------------------
 
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.convert.EntityWriter#write(java.lang.Object, java.lang.Object)
+	 */
 	@Override
 	public void write(Object source, OutboundRow sink) {
 
@@ -313,6 +337,11 @@ private Object getPotentiallyConvertedSimpleWrite(@Nullable Object value) {
 		return Enum.class.isAssignableFrom(value.getClass()) ? ((Enum<?>) value).name() : value;
 	}
 
+	/* 
+	 * (non-Javadoc)
+	 * @see org.springframework.data.r2dbc.convert.R2dbcConverter#getArrayValue(org.springframework.data.r2dbc.dialect.ArrayColumns, org.springframework.data.relational.core.mapping.RelationalPersistentProperty, java.lang.Object)
+	 */
+	@Override
 	public Object getArrayValue(ArrayColumns arrayColumns, RelationalPersistentProperty property, Object value) {
 
 		Class<?> targetType = arrayColumns.getArrayType(property.getActualType());
@@ -337,6 +366,7 @@ public Object getArrayValue(ArrayColumns arrayColumns, RelationalPersistentPrope
 	 * @param object must not be {@literal null}.
 	 * @return
 	 */
+	@Override
 	@SuppressWarnings("unchecked")
 	public <T> BiFunction<Row, RowMetadata, T> populateIdIfNecessary(T object) {
 

src/main/java/org/springframework/data/r2dbc/convert/R2dbcConverter.java

@@ -71,4 +71,14 @@ public interface R2dbcConverter
 	 * @return
 	 */
 	<T> BiFunction<Row, RowMetadata, T> populateIdIfNecessary(T object);
+
+	/**
+	 * Reads the given source into the given type.
+	 *
+	 * @param type they type to convert the given source to.
+	 * @param source the source to create an object of the given type from.
+	 * @param metadata the {@link RowMetadata}.
+	 * @return
+	 */
+	<R> R read(Class<R> type, Row source, RowMetadata metadata);
 }

src/test/java/org/springframework/data/r2dbc/convert/EntityRowMapperUnitTests.java

@@ -7,13 +7,15 @@
 import io.r2dbc.spi.RowMetadata;
 import lombok.RequiredArgsConstructor;
 
+import java.util.Collection;
 import java.util.List;
 import java.util.Set;
 
+import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.mockito.junit.MockitoJUnitRunner;
-import org.springframework.data.r2dbc.convert.EntityRowMapper;
+
 import org.springframework.data.r2dbc.core.DefaultReactiveDataAccessStrategy;
 import org.springframework.data.r2dbc.dialect.PostgresDialect;
 
@@ -30,6 +32,14 @@ public class EntityRowMapperUnitTests {
 
 	Row rowMock = mock(Row.class);
 	RowMetadata metadata = mock(RowMetadata.class);
+	Collection<String> columns = mock(Collection.class);
+
+	@Before
+	public void before() {
+
+		when(columns.contains(anyString())).thenReturn(true);
+		when(metadata.getColumnNames()).thenReturn(columns);
+	}
 
 	@Test // gh-22
 	public void shouldMapSimpleEntity() {

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

@@ -29,13 +29,13 @@
 import java.time.LocalTime;
 import java.time.OffsetDateTime;
 import java.time.ZonedDateTime;
+import java.util.Collection;
 import java.util.UUID;
 import java.util.function.BiConsumer;
 import java.util.function.Function;
 
 import org.junit.Test;
-import org.springframework.data.r2dbc.core.DefaultReactiveDataAccessStrategy;
-import org.springframework.data.r2dbc.core.ReactiveDataAccessStrategy;
+
 import org.springframework.data.r2dbc.dialect.Dialect;
 import org.springframework.data.r2dbc.mapping.SettableValue;
 
@@ -177,6 +177,9 @@ private <T> void testType(BiConsumer<PrimitiveTypes, T> setter, Function<Primiti
 		ReactiveDataAccessStrategy strategy = getStrategy();
 		Row rowMock = mock(Row.class);
 		RowMetadata metadataMock = mock(RowMetadata.class);
+		Collection<String> columnNames = mock(Collection.class);
+		when(metadataMock.getColumnNames()).thenReturn(columnNames);
+		when(columnNames.contains(fieldname)).thenReturn(true);
 
 		PrimitiveTypes toSave = new PrimitiveTypes();
 		setter.accept(toSave, testValue);

src/test/java/org/springframework/data/r2dbc/repository/H2R2dbcRepositoryIntegrationTests.java

@@ -81,7 +81,7 @@ interface H2LegoSetRepository extends LegoSetRepository {
 		Flux<LegoSet> findByNameContains(String name);
 
 		@Override
-		@Query("SELECT * FROM legoset")
+		@Query("SELECT name FROM legoset")
 		Flux<Named> findAsProjection();
 
 		@Override

src/test/java/org/springframework/data/r2dbc/repository/MySqlR2dbcRepositoryIntegrationTests.java

@@ -85,7 +85,7 @@ interface MySqlLegoSetRepository extends LegoSetRepository {
 		Flux<LegoSet> findByNameContains(String name);
 
 		@Override
-		@Query("SELECT * FROM legoset")
+		@Query("SELECT name FROM legoset")
 		Flux<Named> findAsProjection();
 
 		@Override

src/test/java/org/springframework/data/r2dbc/repository/PostgresR2dbcRepositoryIntegrationTests.java

@@ -85,7 +85,7 @@ interface PostgresLegoSetRepository extends LegoSetRepository {
 		Flux<LegoSet> findByNameContains(String name);
 
 		@Override
-		@Query("SELECT * FROM legoset")
+		@Query("SELECT name FROM legoset")
 		Flux<Named> findAsProjection();
 
 		@Override

src/test/java/org/springframework/data/r2dbc/repository/SqlServerR2dbcRepositoryIntegrationTests.java

@@ -90,7 +90,7 @@ interface SqlServerLegoSetRepository extends LegoSetRepository {
 		Flux<LegoSet> findByNameContains(String name);
 
 		@Override
-		@Query("SELECT * FROM legoset")
+		@Query("SELECT name FROM legoset")
 		Flux<Named> findAsProjection();
 
 		@Override