`PropertyAccessingMethodInterceptor` fails with `IllegalStateException` when target method is bridged

[sivaprasadreddy]

I have used Spring Data JPA DTO interface-based projection many times and it worked just fine.
But yesterday I came across an interesting issue that is happening only under certain specific combination such as follows:

I have a BaseEntity as follows:

@MappedSuperclass
class BaseEntity {
    @Column(name = "created_at")
    protected LocalDateTime createdAt;

    @PrePersist
    void prePersist() {
        createdAt = LocalDateTime.now();
    }
    //setter & getter
}

I have a JPA entity Post extending BaseEntity class as follows:

@Entity
@Table(name = "posts")
public class Post extends BaseEntity {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "title", nullable = false, length = 150)
    private String title;

    @Column(name = "slug", nullable = false, unique = true)
    private String slug;

    @Column(name = "content", nullable = false)
    private String content;

    //setters & getters
}

I have created a Interface Projections as follows:

public interface PostProjection {
    Long getId();
    String getTitle();
    String getSlug();
    String getContent();
    LocalDateTime getCreatedAt();
}

Now I have PostRepository as follows:

public interface PostRepository extends JpaRepository<Post, Long> {
    List<PostProjection> findAllBy();

    @Query("from Post")
    List<PostProjection> findAllPosts();
}

The problem: When I get List<PostProjection> by calling postRepository.findAllBy(), everything is working fine. But when I get List<PostProjection> by calling postRepository.findAllPosts() and then try to access postProjection.getCreatedAt() method then it is throwing the following Exception:

**java.lang.IllegalStateException: Invoked method is not a property accessor**
	at org.springframework.data.projection.PropertyAccessingMethodInterceptor.invoke(PropertyAccessingMethodInterceptor.java:66) ~[spring-data-commons-3.4.0.jar:3.4.0]
	at org.springframework.data.projection.ProjectingMethodInterceptor.invoke(ProjectingMethodInterceptor.java:71) ~[spring-data-commons-3.4.0.jar:3.4.0]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.2.0.jar:6.2.0]
	at org.springframework.data.projection.ProxyProjectionFactory$TargetAwareMethodInterceptor.invoke(ProxyProjectionFactory.java:243) ~[spring-data-commons-3.4.0.jar:3.4.0]
	at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:184) ~[spring-aop-6.2.0.jar:6.2.0]
	at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:223) ~[spring-aop-6.2.0.jar:6.2.0]
	at jdk.proxy2/jdk.proxy2.$Proxy123.getCreatedAt(Unknown Source) ~[na:na]

Observations:

• This Exception is occurring only when I access methods from super class(BaseEntity)
• This Exception is occurring only when I use @Query("...")

Here is a minimal reproducer: https://github.com/siva-attic/spring-data-jpa-projection-issue

[mp911de]

This is an interesting effect of mixed visibilities. BaseEntity is package-protected, Post is public. When we look up the target method (method with arguments on the target type Post), we get returned Post.getCreatedAt().

Looking at the byte code, the compiler generates a bridge synthetic method to invoke its parent's getCreatedAt() method.

Interestingly, if we align visibilities (all public or all package-private), the target method resolves to BaseEntity.getCreatedAt() as the compiler no longer generates a bridge synthetic method.

I think we could filter synthetic methods if we walk the inheritance tree to mitigate the issue.

[quaff]

Duplicate of #3159