DATAMONGO-1907 - Do not throw an exception in ReactiveQueryByExampleExecutor.findOne() on empty result

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/repository/support/SimpleReactiveMongoRepository.java

@@ -45,6 +45,7 @@
  * @author Mark Paluch
  * @author Oliver Gierke
  * @author Christoph Strobl
+ * @author Ruben J Garcia
  * @since 2.0
  */
 @RequiredArgsConstructor
@@ -97,7 +98,7 @@ public <S extends T> Mono<S> findOne(Example<S> example) {
 return Mono.error(new IncorrectResultSizeDataAccessException(1));
 }
 return Mono.just(vals.iterator().next());
-}).single();
+}).next();
 }
 
 /*

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/repository/SimpleReactiveMongoRepositoryTests.java

@@ -54,6 +54,7 @@
  *
  * @author Mark Paluch
  * @author Christoph Strobl
+ * @author Ruben J Garcia
  */
 @RunWith(SpringJUnit4ClassRunner.class)
 @ContextConfiguration("classpath:reactive-infrastructure.xml")
@@ -441,6 +442,14 @@ public void findOneShouldEmitIncorrectResultSizeDataAccessExceptionWhenMoreThanO
 StepVerifier.create(repository.findOne(example)).expectError(IncorrectResultSizeDataAccessException.class);
 }
 
+@Test // DATAMONGO-1907
+public void existsByExampleShouldReturnNonExistingWithoutThrowException() {
+
+Example<ReactivePerson> example = Example.of(new ReactivePerson("foo", "bar", -1));
+
+StepVerifier.create(repository.findOne(example)).verifyComplete();
+}
+
 interface ReactivePersonRepostitory extends ReactiveMongoRepository<ReactivePerson, String> {
 
 Flux<ReactivePerson> findByLastname(String lastname);