DATAJDBC-266 - Entities referenced by 1:1 don't need an Id.

pom.xml

@@ -5,7 +5,7 @@
 
     <groupId>org.springframework.data</groupId>
     <artifactId>spring-data-jdbc</artifactId>
-    <version>1.1.0.BUILD-SNAPSHOT</version>
+    <version>1.1.0.DATAJDBC-266-SNAPSHOT</version>
 
 	<name>Spring Data JDBC</name>
 	<description>Spring Data module for JDBC repositories.</description>

src/main/java/org/springframework/data/jdbc/core/EntityRowMapper.java

@@ -21,7 +21,6 @@
 
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.mapping.MappingException;
-import org.springframework.data.mapping.PersistentProperty;
 import org.springframework.data.mapping.PersistentPropertyAccessor;
 import org.springframework.data.mapping.PreferredConstructor;
 import org.springframework.data.relational.core.conversion.RelationalConverter;
@@ -118,29 +117,30 @@ private T populateProperties(T result, ResultSet resultSet) {
 	@Nullable
 	private Object readFrom(ResultSet resultSet, RelationalPersistentProperty property, String prefix) {
 
-		try {
-
-			if (property.isEntity()) {
-				return readEntityFrom(resultSet, property);
-			}
+		if (property.isEntity()) {
+			return readEntityFrom(resultSet, property);
+		}
 
-			return converter.readValue(resultSet.getObject(prefix + property.getColumnName()), property.getTypeInformation());
+		Object value = getObjectFromResultSet(resultSet, prefix + property.getColumnName());
+		return converter.readValue(value, property.getTypeInformation());
 
-		} catch (SQLException o_O) {
-			throw new MappingException(String.format("Could not read property %s from result set!", property), o_O);
-		}
 	}
 
 	@Nullable
-	private <S> S readEntityFrom(ResultSet rs, PersistentProperty<?> property) {
+	private <S> S readEntityFrom(ResultSet rs, RelationalPersistentProperty property) {
 
 		String prefix = property.getName() + "_";
 
 		@SuppressWarnings("unchecked")
 		RelationalPersistentEntity<S> entity = (RelationalPersistentEntity<S>) context
 				.getRequiredPersistentEntity(property.getActualType());
 
-		if (readFrom(rs, entity.getRequiredIdProperty(), prefix) == null) {
+		RelationalPersistentProperty idProperty = entity.getIdProperty();
+
+		if ((idProperty != null //
+				? readFrom(rs, idProperty, prefix) //
+				: getObjectFromResultSet(rs, prefix + property.getReverseColumnName()) //
+		) == null) {
 			return null;
 		}
 
@@ -155,6 +155,16 @@ private <S> S readEntityFrom(ResultSet rs, PersistentProperty<?> property) {
 		return instance;
 	}
 
+	@Nullable
+	private Object getObjectFromResultSet(ResultSet rs, String backreferenceName) {
+
+		try {
+			return rs.getObject(backreferenceName);
+		} catch (SQLException o_O) {
+			throw new MappingException(String.format("Could not read value %s from result set!", backreferenceName), o_O);
+		}
+	}
+
 	private <S> S createInstance(RelationalPersistentEntity<S> entity, ResultSet rs, String prefix) {
 
 		return converter.createInstance(entity, parameter -> {

src/main/java/org/springframework/data/jdbc/core/SqlGenerator.java

@@ -201,6 +201,17 @@ private void addColumnsAndJoinsForOneToOneReferences(SelectBuilder builder) {
 								.as(joinAlias + "_" + refProperty.getColumnName()) //
 				);
 			}
+
+			// if the referenced property doesn't have an id, include the back reference in the select list.
+			// this enables determining if the referenced entity is present or null.
+			if (!refEntity.hasIdProperty()) {
+
+				builder.column( //
+						cb -> cb.tableAlias(joinAlias) //
+								.column(property.getReverseColumnName()) //
+								.as(joinAlias + "_" + property.getReverseColumnName()) //
+				);
+			}
 		}
 	}
 

src/test/java/org/springframework/data/jdbc/core/AggregateTemplateIntegrationTests.java

@@ -210,6 +210,52 @@ public void changeReferencedEntity() {
 		assertThat(reloadedLegoSet.manual.content).isEqualTo("new content");
 	}
 
+	@Test // DATAJDBC-266
+	public void oneToOneChildWithoutId() {
+
+		OneToOneParent parent = new OneToOneParent();
+
+		parent.content = "parent content";
+		parent.child = new OneToOneChildNoId();
+		parent.child.content = "child content";
+
+		template.save(parent);
+
+		OneToOneParent reloaded = template.findById(parent.id, OneToOneParent.class);
+
+		assertThat(reloaded.child.content).isEqualTo("child content");
+	}
+
+	@Test // DATAJDBC-266
+	public void oneToOneNullChildWithoutId() {
+
+		OneToOneParent parent = new OneToOneParent();
+
+		parent.content = "parent content";
+		parent.child = null;
+
+		template.save(parent);
+
+		OneToOneParent reloaded = template.findById(parent.id, OneToOneParent.class);
+
+		assertThat(reloaded.child).isNull();
+	}
+
+	@Test // DATAJDBC-266
+	public void oneToOneNullAttributes() {
+
+		OneToOneParent parent = new OneToOneParent();
+
+		parent.content = "parent content";
+		parent.child = new OneToOneChildNoId();
+
+		template.save(parent);
+
+		OneToOneParent reloaded = template.findById(parent.id, OneToOneParent.class);
+
+		assertThat(reloaded.child).isNotNull();
+	}
+
 	private static LegoSet createLegoSet() {
 
 		LegoSet entity = new LegoSet();
@@ -241,6 +287,18 @@ static class Manual {
 
 	}
 
+	static class OneToOneParent {
+
+		@Id private Long id;
+		private String content;
+
+		private OneToOneChildNoId child;
+	}
+
+	static class OneToOneChildNoId {
+		private String content;
+	}
+
 	@Configuration
 	@Import(TestConfiguration.class)
 	static class Config {

src/test/java/org/springframework/data/jdbc/core/SqlGeneratorUnitTests.java

@@ -186,6 +186,19 @@ public void getInsertForEmptyColumnList() {
 		assertThat(insert).endsWith("()");
 	}
 
+	@Test // DATAJDBC-266
+	public void joinForOneToOneWithoutIdIncludesTheBackReferenceOfTheOuterJoin() {
+
+		SqlGenerator sqlGenerator = createSqlGenerator(ParentOfNoIdChild.class);
+
+		String findAll = sqlGenerator.getFindAll();
+
+		assertThat(findAll).containsSequence(
+				"SELECT",
+				"child.parent_of_no_id_child AS child_parent_of_no_id_child",
+				"FROM");
+	}
+
 	private PersistentPropertyPath<RelationalPersistentProperty> getPath(String path, Class<?> base) {
 		return PersistentPropertyPathTestUtils.getPath(context, path, base);
 	}
@@ -220,6 +233,15 @@ static class Element {
 		String content;
 	}
 
+	static class ParentOfNoIdChild {
+		@Id Long id;
+		NoIdChild child;
+	}
+
+	static class NoIdChild {
+
+	}
+
 	private static class PrefixingNamingStrategy implements NamingStrategy {
 
 		@Override

src/test/resources/org.springframework.data.jdbc.core/AggregateTemplateIntegrationTests-hsql.sql

@@ -3,3 +3,6 @@ CREATE TABLE MANUAL ( id BIGINT GENERATED BY DEFAULT AS IDENTITY(START WITH 1) P
 
 ALTER TABLE MANUAL ADD FOREIGN KEY (LEGO_SET)
 REFERENCES LEGO_SET(id);
+
+CREATE TABLE ONE_TO_ONE_PARENT ( id BIGINT GENERATED BY DEFAULT AS IDENTITY(START WITH 1) PRIMARY KEY, content VARCHAR(30));
+CREATE TABLE One_To_One_Child_No_Id (ONE_TO_ONE_PARENT INTEGER PRIMARY KEY, content VARCHAR(30));

src/test/resources/org.springframework.data.jdbc.core/AggregateTemplateIntegrationTests-mariadb.sql

@@ -3,3 +3,6 @@ CREATE TABLE MANUAL ( id BIGINT AUTO_INCREMENT PRIMARY KEY, LEGO_SET BIGINT, CON
 
 ALTER TABLE MANUAL ADD FOREIGN KEY (LEGO_SET)
 REFERENCES LEGO_SET(id);
+
+CREATE TABLE ONE_TO_ONE_PARENT ( id BIGINT AUTO_INCREMENT PRIMARY KEY, content VARCHAR(30));
+CREATE TABLE One_To_One_Child_No_Id (ONE_TO_ONE_PARENT INTEGER PRIMARY KEY, content VARCHAR(30));

src/test/resources/org.springframework.data.jdbc.core/AggregateTemplateIntegrationTests-mysql.sql

@@ -3,3 +3,6 @@ CREATE TABLE MANUAL ( id BIGINT AUTO_INCREMENT PRIMARY KEY, LEGO_SET BIGINT, CON
 
 ALTER TABLE MANUAL ADD FOREIGN KEY (LEGO_SET)
 REFERENCES LEGO_SET(id);
+
+CREATE TABLE ONE_TO_ONE_PARENT ( id BIGINT AUTO_INCREMENT PRIMARY KEY, content VARCHAR(30));
+CREATE TABLE One_To_One_Child_No_Id (ONE_TO_ONE_PARENT INTEGER PRIMARY KEY, content VARCHAR(30));

src/test/resources/org.springframework.data.jdbc.core/AggregateTemplateIntegrationTests-postgres.sql

@@ -6,3 +6,6 @@ CREATE TABLE MANUAL ( id SERIAL PRIMARY KEY, LEGO_SET BIGINT, CONTENT VARCHAR(20
 
 ALTER TABLE MANUAL ADD FOREIGN KEY (LEGO_SET)
 REFERENCES LEGO_SET(id);
+
+CREATE TABLE ONE_TO_ONE_PARENT ( id SERIAL PRIMARY KEY, content VARCHAR(30));
+CREATE TABLE One_To_One_Child_No_Id (ONE_TO_ONE_PARENT INTEGER PRIMARY KEY, content VARCHAR(30));