DATAJPA-1110 - Adapt to QueryByExampleExecutor API changes.

Use Optional as return type for findOne(Example example).

Related ticket: DATACMNS-1058.

Original pull request: #201.

Author: christophstrobl

src/main/java/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java

@@ -398,11 +398,13 @@ public List<T> findAll(Specification<T> spec, Sort sort) {
 	 * @see org.springframework.data.repository.query.QueryByExampleExecutor#findOne(org.springframework.data.domain.Example)
 	 */
 	@Override
-	public <S extends T> S findOne(Example<S> example) {
+	public <S extends T> Optional<S> findOne(Example<S> example) {
+
 		try {
-			return getQuery(new ExampleSpecification<S>(example), example.getProbeType(), (Sort) null).getSingleResult();
+			return Optional
+					.of(getQuery(new ExampleSpecification<S>(example), example.getProbeType(), (Sort) null).getSingleResult());
 		} catch (NoResultException e) {
-			return null;
+			return Optional.empty();
 		}
 	}
 

src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java

@@ -43,6 +43,7 @@
 import javax.persistence.criteria.Predicate;
 import javax.persistence.criteria.Root;
 
+import org.assertj.core.api.Assertions;
 import org.hamcrest.Matchers;
 import org.junit.Assume;
 import org.junit.Before;
@@ -2093,9 +2094,8 @@ public void findOneByExampleWithExcludedAttributes() {
 		prototype.setAge(28);
 
 		Example<User> example = Example.of(prototype, matching().withIgnorePaths("createdAt"));
-		User users = repository.findOne(example);
 
-		assertThat(users, is(firstUser));
+		Assertions.assertThat(repository.findOne(example)).contains(firstUser);
 	}
 
 	@Test // DATAJPA-218