Add missing @Nullable annotations to QueryByExampleExecutor.findBy(…) and QuerydslPredicateExecutor.findBy(…).

Closes spring-projects#3346

Author: mp911de

src/main/java/org/springframework/data/querydsl/QuerydslPredicateExecutor.java

@@ -18,6 +18,8 @@
 import java.util.Optional;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.domain.Sort;
@@ -125,5 +127,6 @@ public interface QuerydslPredicateExecutor<T> {
 	 * @return all entities matching the given {@link Predicate}.
 	 * @since 2.6
 	 */
-	<S extends T, R> R findBy(Predicate predicate, Function<FluentQuery.FetchableFluentQuery<S>, R> queryFunction);
+	<S extends T, R extends @Nullable Object> R findBy(Predicate predicate,
+			Function<FluentQuery.FetchableFluentQuery<S>, R> queryFunction);
 }

src/main/java/org/springframework/data/repository/query/QueryByExampleExecutor.java

@@ -18,6 +18,8 @@
 import java.util.Optional;
 import java.util.function.Function;
 
+import org.jspecify.annotations.Nullable;
+
 import org.springframework.data.domain.Example;
 import org.springframework.data.domain.Page;
 import org.springframework.data.domain.Pageable;
@@ -105,5 +107,6 @@ public interface QueryByExampleExecutor<T> {
 	 * @return all entities matching the given {@link Example}.
 	 * @since 2.6
 	 */
-	<S extends T, R> R findBy(Example<S> example, Function<FluentQuery.FetchableFluentQuery<S>, R> queryFunction);
+	<S extends T, R extends @Nullable Object> R findBy(Example<S> example,
+			Function<FluentQuery.FetchableFluentQuery<S>, R> queryFunction);
 }