DATAJPA-1074 - Polishing.

Slightly changed the implementation to reject IsEmpty for non-collection properties. Minor formatting in unit tests.

Original pull request: #190.

Author: odrotbohm

src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java

@@ -309,11 +309,14 @@ public Predicate build() {
 							upperIfIgnoreCase(provider.next(part).getExpression()));
 				case IS_EMPTY:
 				case IS_NOT_EMPTY:
-					if (property.getLeafProperty().isCollection()) {
-						Expression<Collection<Object>> emptyExpression = traversePath(root, property);
-						return type.equals(IS_NOT_EMPTY) ? builder.isNotEmpty(emptyExpression)
-								: builder.isEmpty(emptyExpression);
+
+					if (!property.getLeafProperty().isCollection()) {
+						throw new IllegalArgumentException("IsEmpty / IsNotEmpty can only be used on collection properties!");
 					}
+
+					Expression<Collection<Object>> collectionPath = traversePath(root, property);
+					return type.equals(IS_NOT_EMPTY) ? builder.isNotEmpty(collectionPath) : builder.isEmpty(collectionPath);
+
 				default:
 					throw new IllegalArgumentException("Unsupported keyword " + type);
 			}

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

@@ -121,7 +121,7 @@ public void shouldLimitExistsProjectionQueries() throws Exception {
 		JpaQueryMethod queryMethod = getQueryMethod("existsByFirstname", String.class);
 		PartTreeJpaQuery jpaQuery = new PartTreeJpaQuery(queryMethod, entityManager, provider);
 
-		Query query = jpaQuery.createQuery(new Object[]{"Matthews"});
+		Query query = jpaQuery.createQuery(new Object[] { "Matthews" });
 
 		assertThat(query.getMaxResults(), is(1));
 	}
@@ -132,7 +132,7 @@ public void shouldSelectAliasedIdForExistsProjectionQueries() throws Exception {
 		JpaQueryMethod queryMethod = getQueryMethod("existsByFirstname", String.class);
 		PartTreeJpaQuery jpaQuery = new PartTreeJpaQuery(queryMethod, entityManager, provider);
 
-		Query query = jpaQuery.createQuery(new Object[]{"Matthews"});
+		Query query = jpaQuery.createQuery(new Object[] { "Matthews" });
 
 		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY)), containsString(".id from User as"));
 	}
@@ -159,6 +159,15 @@ public void isNotEmptyCollection() throws Exception {
 		assertThat(HibernateUtils.getHibernateQuery(getValue(query, PROPERTY)), endsWith("roles is not empty"));
 	}
 
+	@Test(expected = IllegalArgumentException.class) // DATAJPA-1074
+	public void rejectsIsEmptyOnNonCollectionProperty() throws Exception {
+
+		JpaQueryMethod method = getQueryMethod("findByFirstnameIsEmpty");
+		AbstractJpaQuery jpaQuery = new PartTreeJpaQuery(method, entityManager, provider);
+
+		jpaQuery.createQuery(new Object[] { "Oliver" });
+	}
+
 	private void testIgnoreCase(String methodName, Object... values) throws Exception {
 
 		Class<?>[] parameterTypes = new Class[values.length];
@@ -219,5 +228,7 @@ interface UserRepository extends Repository<User, Long> {
 		List<User> findByRolesIsEmpty();
 
 		List<User> findByRolesIsNotEmpty();
+
+		List<User> findByFirstnameIsEmpty();
 	}
 }