DATAJPA-401 - Non-optional associations don't trigger join creation anymore.

When building Expression instances for attribute traversals we now inspect the mapping annotation to detect non-optional associations and prevent an extra left join from being created. This is because the join is only necessary to not drop null values from the result.

Added integration tests for Hibernate, EclipseLink and OpenJpa. EclipseLink needs a bit of special treatment as it exposes the inner join being created for a plain ….get(…) attribute traversal.

src/test/java/org/springframework/data/jpa/domain/sample/Customer.java

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.domain.sample;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+
+/**
+ * @author Oliver Gierke
+ */
+@Entity
+public class Customer {
+
+	@Id Long id;
+}

src/test/java/org/springframework/data/jpa/domain/sample/Order.java

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.domain.sample;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.ManyToOne;
+import javax.persistence.Table;
+
+/**
+ * @author Oliver Gierke
+ */
+@Entity
+@Table(name = "ORDERS")
+public class Order {
+
+	@Id Long id;
+	@ManyToOne(optional = false) Customer customer;
+}

src/test/java/org/springframework/data/jpa/repository/query/EclipseLinkQueryUtilsIntegrationTests.java

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.repository.query;
+
+import static org.hamcrest.Matchers.*;
+import static org.junit.Assert.*;
+
+import java.util.Set;
+
+import javax.persistence.criteria.Join;
+import javax.persistence.criteria.JoinType;
+import javax.persistence.criteria.Root;
+
+import org.springframework.data.jpa.domain.sample.Order;
+import org.springframework.test.context.ContextConfiguration;
+
+/**
+ * @author Oliver Gierke
+ */
+@ContextConfiguration("classpath:eclipselink.xml")
+public class EclipseLinkQueryUtilsIntegrationTests extends QueryUtilsIntegrationTests {
+
+	/**
+	 * Required as EclipseLink generates an inner join for plain association traversal.
+	 */
+	@Override
+	protected void assertNoJoinRequestedForOptionalAssociation(Root<Order> root) {
+
+		Set<Join<Order, ?>> joins = root.getJoins();
+		assertThat(joins, hasSize(1));
+
+		Join<Order, ?> join = joins.iterator().next();
+		assertThat(join.getAttribute().getName(), is("manager"));
+		assertThat(join.getJoinType(), is(JoinType.INNER));
+	}
+}

src/test/java/org/springframework/data/jpa/repository/query/OpenJpaQueryUtilsIntegrationTests.java

@@ -0,0 +1,26 @@
+/*
+ * Copyright 2013 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.repository.query;
+
+import org.springframework.test.context.ContextConfiguration;
+
+/**
+ * @author Oliver Gierke
+ */
+@ContextConfiguration("classpath:openjpa.xml")
+public class OpenJpaQueryUtilsIntegrationTests extends QueryUtilsIntegrationTests {
+
+}

src/test/java/org/springframework/data/jpa/repository/query/QueryUtilsIntegrationTests.java

@@ -26,6 +26,7 @@ import javax.persistence.criteria.Root;
 
 import org.junit.Test;
 import org.junit.runner.RunWith;
+import org.springframework.data.jpa.domain.sample.Order;
 import org.springframework.data.jpa.domain.sample.User;
 import org.springframework.data.mapping.PropertyPath;
 import org.springframework.test.context.ContextConfiguration;
@@ -60,4 +61,36 @@ public class QueryUtilsIntegrationTests {
 
 		assertThat(from.getJoins(), hasSize(1));
 	}
+
+	/**
+	 * @see DATAJPA-401
+	 */
+	@Test
+	public void createsJoinForOptionalAssociation() {
+
+		CriteriaBuilder builder = em.getCriteriaBuilder();
+		CriteriaQuery<User> query = builder.createQuery(User.class);
+		Root<User> root = query.from(User.class);
+
+		QueryUtils.toExpressionRecursively(root, PropertyPath.from("manager", User.class));
+
+		assertThat(root.getJoins(), hasSize(1));
+	}
+
+	/**
+	 * @see DATAJPA-401
+	 */
+	@Test
+	public void doesNotCreateAJoinForNonOptionalAssociation() {
+
+		CriteriaBuilder builder = em.getCriteriaBuilder();
+		CriteriaQuery<Order> query = builder.createQuery(Order.class);
+		Root<Order> root = query.from(Order.class);
+
+		QueryUtils.toExpressionRecursively(root, PropertyPath.from("customer", Order.class));
+	}
+
+	protected void assertNoJoinRequestedForOptionalAssociation(Root<Order> root) {
+		assertThat(root.getJoins(), is(empty()));
+	}
 }