DATAJPA-476 - Mitigate spec violations in Hibernate for query creation.

Hibernate invalidly returns null for getModel() on its PluralAttribute implementation which causes the necessity for joins not having been detected previously.

We now fall back to joining in case we don't find a Model and deal with a PluralAttribute.

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

@@ -18,7 +18,14 @@ package org.springframework.data.jpa.repository.query;
 import static org.hamcrest.Matchers.*;
 import static org.junit.Assert.*;
 
+import java.util.Set;
+
+import javax.persistence.Entity;
 import javax.persistence.EntityManager;
+import javax.persistence.EntityManagerFactory;
+import javax.persistence.Id;
+import javax.persistence.OneToMany;
+import javax.persistence.Persistence;
 import javax.persistence.PersistenceContext;
 import javax.persistence.criteria.CriteriaBuilder;
 import javax.persistence.criteria.CriteriaQuery;
@@ -105,7 +112,42 @@ public class QueryUtilsIntegrationTests {
 		assertThat(root.getJoins(), hasSize(1));
 	}
 
+	/**
+	 * @see DATAJPA-476
+	 */
+	@Test
+	public void traversesPluralAttributeCorrectly() {
+
+		EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory("merchant");
+		CriteriaBuilder builder = entityManagerFactory.createEntityManager().getCriteriaBuilder();
+		CriteriaQuery<Merchant> query = builder.createQuery(Merchant.class);
+		Root<Merchant> root = query.from(Merchant.class);
+
+		QueryUtils.toExpressionRecursively(root, PropertyPath.from("employeesCredentialsUid", Merchant.class));
+	}
+
 	protected void assertNoJoinRequestedForOptionalAssociation(Root<Order> root) {
 		assertThat(root.getJoins(), is(empty()));
 	}
+
+	@Entity
+	static class Merchant {
+
+		@Id String id;
+		@OneToMany Set<Employee> employees;
+	}
+
+	@Entity
+	static class Employee {
+
+		@Id String id;
+		@OneToMany Set<Credential> credentials;
+	}
+
+	@Entity
+	static class Credential {
+
+		@Id String id;
+		String uid;
+	}
 }