Verify that single-parameter DTOs work with JPQL queries.

Closes #1869.

Author: gregturn

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

@@ -25,7 +25,6 @@
 import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.extension.ExtendWith;
-
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.dao.InvalidDataAccessApiUsageException;
 import org.springframework.data.domain.Page;
@@ -288,4 +287,9 @@ void rejectsStreamExecutionIfNoSurroundingTransactionActive() {
 	void executesNamedQueryWithConstructorExpression() {
 		userRepository.findByNamedQueryWithConstructorExpression();
 	}
+
+	@Test // GH-1869
+	void executesNamedQueryWithSingleConstructorExpression() {
+		userRepository.findByNamedQueryWithSingleConstructor("Dave");
+	}
 }

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/sample/FirstNameDto.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2018-2022 the original author or authors.
+ *
+ * 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
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jpa.repository.sample;
+
+/**
+ * Verify that single argument DTOs work with JPQL new object queries.
+ *
+ * @author Greg Turnquist
+ * @see https://github.com/spring-projects/spring-data-jpa/issues/1869
+ */
+class FirstNameDto {
+
+	private String firstname;
+
+	public FirstNameDto(String firstname) {
+		this.firstname = firstname;
+	}
+}

spring-data-jpa/src/test/java/org/springframework/data/jpa/repository/sample/UserRepository.java

@@ -607,6 +607,10 @@ Page<User> findAllOrderedBySpecialNameMultipleParams(@Param("name") String name,
 	// DATAJPA-1334
 	List<NameOnlyDto> findByNamedQueryWithConstructorExpression();
 
+	// GH-1869
+	@Query("SELECT new org.springframework.data.jpa.repository.sample.FirstNameDto(u.firstname) from User u where u.firstname = :firstname")
+	List<FirstNameDto> findByNamedQueryWithSingleConstructor(@Param("firstname") String firstname);
+
 	// DATAJPA-1519
 	@Query("select u from User u where u.lastname like %?#{escape([0])}% escape ?#{escapeCharacter()}")
 	List<User> findContainingEscaped(String namePart);