DATAMONGO-1690 - Adapt to QuerydslPredicateExecutor API changes.

We now return Optional<T> for QuerydslPredicateExecutor.findOne(Predicate).

Original pull request #461.
Related ticket: DATACMNS-1059.

Author: christophstrobl

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

@@ -17,7 +17,9 @@
 
 import java.io.Serializable;
 import java.util.List;
+import java.util.Optional;
 
+import org.springframework.dao.IncorrectResultSizeDataAccessException;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
@@ -34,6 +36,7 @@
 import org.springframework.data.repository.support.PageableExecutionUtils;
 import org.springframework.util.Assert;
 
+import com.querydsl.core.NonUniqueResultException;
 import com.querydsl.core.types.EntityPath;
 import com.querydsl.core.types.Expression;
 import com.querydsl.core.types.OrderSpecifier;
@@ -47,6 +50,7 @@
  * @author Oliver Gierke
  * @author Thomas Darimont
  * @author Mark Paluch
+ * @author Christoph Strobl
  */
 public class QueryDslMongoRepository<T, ID extends Serializable> extends SimpleMongoRepository<T, ID>
 		implements QuerydslPredicateExecutor<T> {
@@ -93,11 +97,15 @@ public QueryDslMongoRepository(MongoEntityInformation<T, ID> entityInformation,
 	 * @see org.springframework.data.querydsl.QuerydslPredicateExecutor#findById(com.querydsl.core.types.Predicate)
 	 */
 	@Override
-	public T findOne(Predicate predicate) {
+	public Optional<T> findOne(Predicate predicate) {
 
 		Assert.notNull(predicate, "Predicate must not be null!");
 
-		return createQueryFor(predicate).fetchOne();
+		try {
+			return Optional.ofNullable(createQueryFor(predicate).fetchOne());
+		} catch (NonUniqueResultException ex) {
+			throw new IncorrectResultSizeDataAccessException(ex.getMessage(), 1, ex);
+		}
 	}
 
 	/*

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

@@ -917,7 +917,7 @@ public void shouldExecuteFindOnDbRefCorrectly() {
 		dave.setCreator(user);
 		operations.save(dave);
 
-		assertThat(repository.findOne(QPerson.person.creator.eq(user)), is(dave));
+		assertThat(repository.findOne(QPerson.person.creator.eq(user)).get(), is(dave));
 	}
 
 	@Test // DATAMONGO-969

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

@@ -21,10 +21,12 @@
 import java.util.Arrays;
 import java.util.List;
 
+import org.assertj.core.api.Assertions;
 import org.junit.Before;
 import org.junit.Test;
 import org.junit.runner.RunWith;
 import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.dao.IncorrectResultSizeDataAccessException;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.domain.Sort.Direction;
 import org.springframework.data.mongodb.core.MongoOperations;
@@ -39,6 +41,7 @@
  *
  * @author Thomas Darimont
  * @author Mark Paluch
+ * @author Christoph Strobl
  */
 @ContextConfiguration(
 		locations = "/org/springframework/data/mongodb/repository/PersonRepositoryIntegrationTests-context.xml")
@@ -86,4 +89,19 @@ public void shouldSupportFindAllWithPredicateAndSort() {
 		assertThat(users.get(2).getFirstname(), is(oliver.getFirstname()));
 		assertThat(users, hasItems(carter, dave, oliver));
 	}
+
+	@Test // DATAMONGO-1690
+	public void findOneWithPredicateReturnsResultCorrectly() {
+		Assertions.assertThat(repository.findOne(person.firstname.eq(dave.getFirstname()))).contains(dave);
+	}
+
+	@Test // DATAMONGO-1690
+	public void findOneWithPredicateReturnsOptionalEmptyWhenNoDataFound() {
+		Assertions.assertThat(repository.findOne(person.firstname.eq("batman"))).isNotPresent();
+	}
+
+	@Test(expected = IncorrectResultSizeDataAccessException.class) // DATAMONGO-1690
+	public void findOneWithPredicateThrowsExceptionForNonUniqueResults() {
+		repository.findOne(person.firstname.contains("e"));
+	}
 }