How to filter by child object property with QuerydslPredicate?

Question

I have a "Pet" domain and a "Person" domain, a person may have a pet. Using QuerydslPredicate on my RestController, I would like to return only the persons that have a Pet of type "DOG".

Pet.java

@Entity
public class Pet {

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

    @Column(nullable = false)
    private String name;

    @Enumerated(EnumType.STRING)
    @Column(nullable = false, name = "animal_type")
    private AnimalType type;

    // constructors & getters/setters
}


enum AnimalType {
    DOG, CAT
}

Person.java

@Entity
public class Person {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(nullable = false)
    private String name;

    @Column(nullable = false)
    private String surname;


    @OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.PERSIST)
    @JoinColumn(name = "pet_id")
    private Pet pet;

    // constructors & getters/setters
}

PersonController.java

@RestController
@RequestMapping("persons")
public class PersonController {

    @Autowired
    private PersonRepository personRepository;

    @GetMapping
    public List<Person> getAll(@QuerydslPredicate(root = Person.class) Predicate predicate)
    {
        return (List<Person>) personRepository.findAll(predicate);
    }
}

PersonRepository.java

public interface PersonRepository extends JpaRepository<Person, Long>, QuerydslPredicateExecutor<Person> {
}

I'd like to query only persons that have a dog with a GET request like this:

localhost:8080/persons?pet.type=DOG

But this renders the following error:

{
    "timestamp": "2019-04-09T18:11:23.430+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "Could not access method: Class org.springframework.util.ReflectionUtils can not access a member of class com.example.demo.domain.QPerson with modifiers \"protected\"",
    "path": "/persons"
}

Querying for people named "Tom" works fine though using localhost:8080/persons?name=Tom.

I have this repo available here.

I have already tried solutions from this, this, this, and this stackoverflow questions, but haven't being able to make it work yet.

Answer 1

Just change your querydsl.entityAccessors property in your pom.xml to false (or remove it, the default value is false).

Why this is happening?

In your pom.xml, you have the following configuration:

<querydsl.entityAccessors>true</querydsl.entityAccessors>

This option makes your relationships being created as protected methods in your class, hence your error (https://github.com/querydsl/querydsl/blob/master/querydsl-codegen/src/main/java/com/querydsl/codegen/EntitySerializer.java#L211).

if (config.useEntityAccessors()) {
    writer.protectedField(queryType, field.getEscapedName());
} else {
    writer.publicFinal(queryType, field.getEscapedName());
}