From 59fd61aad831d71339c5b8dd1c0dcfdc245762df Mon Sep 17 00:00:00 2001
From: Oliver Drotbohm <ogierke@pivotal.io>
Date: Tue, 25 Jan 2022 09:15:52 +0100
Subject: [PATCH] Fix potential NullPointerException in JpaQueryCreator.

With the commit for GH-2363, we introduced an unguarded call to ReturnedType.getTypeToRead(), which could return null under certain conditions. Unfortunately Spring Data JPA dod not contain a test case that triggered that scenario.

This commit switches to ReturnedType.getReturnedType() which is non-nullable and lets us inspect the calls results for interfaces, which we need to create the JPA query properly.

Fixes GH-2408
---
 .../data/jpa/repository/query/JpaQueryCreator.java        | 2 +-
 .../data/jpa/repository/UserRepositoryTests.java          | 8 ++++++++
 .../data/jpa/repository/sample/UserRepository.java        | 3 +++
 3 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
index 3eb0762ee..582e58702 100644
--- a/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
+++ b/src/main/java/org/springframework/data/jpa/repository/query/JpaQueryCreator.java
@@ -176,7 +176,7 @@ public class JpaQueryCreator extends AbstractQueryCreator<CriteriaQuery<? extend
 				selections.add(toExpressionRecursively(root, path, true).alias(property));
 			}
 
-			Class<?> typeToRead = returnedType.getTypeToRead();
+			Class<?> typeToRead = returnedType.getReturnedType();
 
 			query = typeToRead.isInterface()
 					? query.multiselect(selections)
diff --git a/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java b/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java
index a4a438e85..08e8ff927 100644
--- a/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java
+++ b/src/test/java/org/springframework/data/jpa/repository/UserRepositoryTests.java
@@ -2621,6 +2621,14 @@ public class UserRepositoryTests {
 		assertThat(repository.findAllDtoProjectedBy()).hasSize(4);
 	}
 
+	@Test // GH-2408, GH-2363
+	void readsDerivedInterfaceProjections() {
+
+		flushTestUsers();
+
+		assertThat(repository.findAllInterfaceProjectedBy()).hasSize(4);
+	}
+
 	private Page<User> executeSpecWithSort(Sort sort) {
 
 		flushTestUsers();
diff --git a/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java b/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java
index 721123ca1..9350b0184 100644
--- a/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java
+++ b/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java
@@ -614,6 +614,9 @@ public interface UserRepository
 	// #2363
 	List<NameOnlyDto> findAllDtoProjectedBy();
 
+	// GH-2408
+	List<NameOnly> findAllInterfaceProjectedBy();
+
 	interface RolesAndFirstname {
 
 		String getFirstname();