Do not use tuple-typed queries for derived count queries.

Prior to this change interface projections used to set useTupleQuery() to true on JpaQueryCreator, which was later also reused to build the count query. This caused trouble when reading results expecting a numeric value.

Closes #4230
Original pull request: #4235

Author: christophstrobl

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/JpaCountQueryCreator.java

@@ -77,6 +77,11 @@ public JpaCountQueryCreator(PartTree tree, ReturnedType returnedType, ParameterM
 		this.distinct = tree.isDistinct();
 	}
 
+	@Override
+	public boolean useTupleQuery() {
+		return false;
+	}
+
 	@Override
 	protected JpqlQueryBuilder.Select buildQuery(Sort sort) {
 

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/PartTreeJpaQuery.java

@@ -68,7 +68,7 @@ public class PartTreeJpaQuery extends AbstractJpaQuery {
 	private final JpaParameters parameters;
 
 	private final QueryPreparer queryPreparer;
-	private final QueryPreparer countQuery;
+	private final CountQueryPreparer countQuery;
 	private final EntityManager em;
 	private final EscapeCharacter escape;
 	private final Lazy<JpaEntityInformation<?, ?>> entityInformation;

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

@@ -1,9 +1,7 @@
 /*
  * Copyright 2011-present the original author or authors.
  *
- * Licensed under the Apache License, Version 2.0 (the "License
-import org.springframework.aop.framework.Advised;
-");
+ * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
  * You may obtain a copy of the License at
  *
@@ -22,6 +20,7 @@
 import jakarta.persistence.EntityManager;
 import jakarta.persistence.PersistenceContext;
 import jakarta.persistence.Query;
+import jakarta.persistence.Tuple;
 import jakarta.persistence.TemporalType;
 
 import java.lang.reflect.Method;
@@ -247,6 +246,20 @@ void allowsCollectionArgForCollectionProperty() throws Exception {
 		new PartTreeJpaQuery(getQueryMethod("findByAttributes", String[].class), entityManager);
 	}
 
+	@Test // GH-4230
+	void countQueryForPagedInterfaceProjectionReturnsScalarAggregate() throws Exception {
+
+		JpaQueryMethod queryMethod = getQueryMethod(ProjectionPagingRepository.class, "findByFirstname", String.class,
+				Pageable.class);
+		PartTreeJpaQuery jpaQuery = new PartTreeJpaQuery(queryMethod, entityManager);
+
+		Query countQuery = jpaQuery
+				.createCountQuery(getAccessor(queryMethod, new Object[] { "Matthews", PageRequest.of(0, 2) }));
+
+		Object total = countQuery.getSingleResult();
+		assertThat(total).isInstanceOf(Number.class).isNotInstanceOf(Tuple.class);
+	}
+
 	private void testIgnoreCase(String methodName, Object... values) throws Exception {
 
 		Class<?>[] parameterTypes = new Class[values.length];
@@ -262,8 +275,14 @@ private void testIgnoreCase(String methodName, Object... values) throws Exceptio
 
 	private JpaQueryMethod getQueryMethod(String methodName, Class<?>... parameterTypes) throws Exception {
 
-		Method method = UserRepository.class.getMethod(methodName, parameterTypes);
-		return new JpaQueryMethod(method, new DefaultRepositoryMetadata(UserRepository.class),
+		return getQueryMethod(UserRepository.class, methodName, parameterTypes);
+	}
+
+	private JpaQueryMethod getQueryMethod(Class<?> repositoryType, String methodName, Class<?>... parameterTypes)
+			throws Exception {
+
+		Method method = repositoryType.getMethod(methodName, parameterTypes);
+		return new JpaQueryMethod(method, new DefaultRepositoryMetadata(repositoryType),
 				new SpelAwareProxyProjectionFactory(), PersistenceProvider.fromEntityManager(entityManager));
 	}
 
@@ -326,4 +345,12 @@ interface UserRepository extends Repository<User, Integer> {
 		List<User> findByAttributes(String... attributes);
 	}
 
+	interface UserNameProjection {
+		String getLastname();
+	}
+
+	interface ProjectionPagingRepository extends Repository<User, Integer> {
+		Page<UserNameProjection> findByFirstname(String firstname, Pageable pageable);
+	}
+
 }