Guard access to identifier property.

We now check in all places where we optionally use the Id property that an entity actually has an Id property and fall back leniently if the entity doesn't have an identifier property.

Also, we use IdentifierAccessor consistently if the property is an identifier property.

See #711

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

@@ -31,6 +31,7 @@ import org.springframework.core.CollectionFactory;
 import org.springframework.core.convert.ConversionService;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.convert.CustomConversions;
+import org.springframework.data.mapping.IdentifierAccessor;
 import org.springframework.data.mapping.MappingException;
 import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
@@ -370,7 +371,14 @@ public class MappingR2dbcConverter extends BasicRelationalConverter implements R
 				continue;
 			}
 
-			Object value = accessor.getProperty(property);
+			Object value;
+
+			if (property.isIdProperty()) {
+				IdentifierAccessor identifierAccessor = entity.getIdentifierAccessor(accessor.getBean());
+				value = identifierAccessor.getIdentifier();
+			} else {
+				value = accessor.getProperty(property);
+			}
 
 			if (value == null) {
 				writeNullInternal(sink, property);
@@ -600,6 +608,10 @@ public class MappingR2dbcConverter extends BasicRelationalConverter implements R
 		Class<?> userClass = ClassUtils.getUserClass(object);
 		RelationalPersistentEntity<?> entity = getMappingContext().getRequiredPersistentEntity(userClass);
 
+		if (!entity.hasIdProperty()) {
+			return (row, rowMetadata) -> object;
+		}
+
 		return (row, metadata) -> {
 
 			PersistentPropertyAccessor<?> propertyAccessor = entity.getPropertyAccessor(object);

src/main/java/org/springframework/data/r2dbc/core/R2dbcEntityTemplate.java

@@ -65,6 +65,7 @@ import org.springframework.data.relational.core.query.CriteriaDefinition;
 import org.springframework.data.relational.core.query.Query;
 import org.springframework.data.relational.core.query.Update;
 import org.springframework.data.relational.core.sql.Expression;
+import org.springframework.data.relational.core.sql.Expressions;
 import org.springframework.data.relational.core.sql.Functions;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.data.relational.core.sql.Table;
@@ -322,7 +323,11 @@ public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAw
 		StatementMapper.SelectSpec selectSpec = statementMapper //
 				.createSelect(tableName) //
 				.doWithTable((table, spec) -> {
-					return spec.withProjection(Functions.count(table.column(entity.getRequiredIdProperty().getColumnName())));
+
+					Expression countExpression = entity.hasIdProperty()
+							? table.column(entity.getRequiredIdProperty().getColumnName())
+							: Expressions.asterisk();
+					return spec.withProjection(Functions.count(countExpression));
 				});
 
 		Optional<CriteriaDefinition> criteria = query.getCriteria();
@@ -834,6 +839,7 @@ public class R2dbcEntityTemplate implements R2dbcEntityOperations, BeanFactoryAw
 	}
 
 	private <T> Query getByIdQuery(T entity, RelationalPersistentEntity<?> persistentEntity) {
+
 		if (!persistentEntity.hasIdProperty()) {
 			throw new MappingException("No id property found for object of type " + persistentEntity.getType() + "!");
 		}

src/main/java/org/springframework/data/r2dbc/repository/query/R2dbcQueryCreator.java

@@ -29,6 +29,7 @@ import org.springframework.data.relational.core.mapping.RelationalPersistentProp
 import org.springframework.data.relational.core.query.Criteria;
 import org.springframework.data.relational.core.sql.Column;
 import org.springframework.data.relational.core.sql.Expression;
+import org.springframework.data.relational.core.sql.Expressions;
 import org.springframework.data.relational.core.sql.Functions;
 import org.springframework.data.relational.core.sql.SqlIdentifier;
 import org.springframework.data.relational.core.sql.Table;
@@ -164,8 +165,11 @@ class R2dbcQueryCreator extends RelationalQueryCreator<PreparedOperation<?>> {
 				.collect(Collectors.toList());
 		} else if (tree.isCountProjection()) {
 
-			SqlIdentifier idColumn = entityMetadata.getTableEntity().getRequiredIdProperty().getColumnName();
-			expressions = Collections.singletonList(Functions.count(table.column(idColumn)));
+			Expression countExpression = entityMetadata.getTableEntity().hasIdProperty()
+					? table.column(entityMetadata.getTableEntity().getRequiredIdProperty().getColumnName())
+					: Expressions.asterisk();
+
+			expressions = Collections.singletonList(Functions.count(countExpression));
 		} else {
 			expressions = dataAccessStrategy.getAllColumns(entityToRead).stream()
 				.map(table::column)

src/test/java/org/springframework/data/r2dbc/convert/MappingR2dbcConverterUnitTests.java

@@ -43,6 +43,7 @@ import org.springframework.data.annotation.Id;
 import org.springframework.data.annotation.Transient;
 import org.springframework.data.convert.ReadingConverter;
 import org.springframework.data.convert.WritingConverter;
+import org.springframework.data.domain.Persistable;
 import org.springframework.data.r2dbc.dialect.PostgresDialect;
 import org.springframework.data.r2dbc.mapping.OutboundRow;
 import org.springframework.data.r2dbc.mapping.R2dbcMappingContext;
@@ -250,6 +251,18 @@ public class MappingR2dbcConverterUnitTests {
 		assertThat(result.person).isNull();
 	}
 
+	@Test // GH-711
+	void writeShouldObtainIdFromIdentifierAccessor() {
+
+		PersistableEntity entity = new PersistableEntity();
+		entity.id = null;
+
+		OutboundRow row = new OutboundRow();
+		converter.write(entity, row);
+
+		assertThat(row).containsEntry(SqlIdentifier.unquoted("id"), Parameter.from(42L));
+	}
+
 	@AllArgsConstructor
 	static class Person {
 		@Id String id;
@@ -406,4 +419,19 @@ public class MappingR2dbcConverterUnitTests {
 			this.name = name;
 		}
 	}
+
+	static class PersistableEntity implements Persistable<Long> {
+
+		@Id String id;
+
+		@Override
+		public Long getId() {
+			return 42L;
+		}
+
+		@Override
+		public boolean isNew() {
+			return false;
+		}
+	}
 }