How do I skip relational data in Spring data JPA?

I have two Entities Type and Nature given below.

Type:

@Entity
@Getter
@Setter
@Table(name = "types")
public class Type {

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

    private String name;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name = "type_id", referencedColumnName = "id")
    private List<Nature> natures;
}

Nature:

@Entity
@Getter
@Setter
@Table(name = "natures")
public class Nature {

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

    private String name;

    private String description;
}

For some cases, I need to get Type data with Nature data.
So my Controller, Service looks like below.

Controller:

@GetMapping("/v1/complaints/types")
public ResponseEntity<List<Type>> getAllType() {
    List<Type> typesList = complaintService.getAllComplaintTypes();
    return new ResponseEntity<>(typesList, HttpStatus.OK);
}

Service:

public List<Type> getAllComplaintTypes() {
    List<Type> typeList = typeRepository.findAll();
    return typeList;
}

That gives me data like this:

    {
        "id": 2,
        "name": "demo type name",
        "natures": [
            {
                "id": 12,
                "name": "nature name 1",
                "description": "nature description 1"
            },
            {
                "id": 14,
                "name": "nature name 2",
                "description": "nature name 2"
            }
        ]
    }

But in some other cases I need only Type data without Nature data.
How can I avoid the Nature data?

It is by default bad practice to fetch eagerly. Switch to fetch type lazy and implement two service methods, one to fetch all (standard via JPA), and one with Nature, done like this in JPA repository:

    @EntityGraph(type = EntityGraph.EntityGraphType.FETCH, attributePaths = "natures")
    @Query("""
            SELECT type
            FROM Type type
            """)
    List<Type> findAllWithNature();

The EntityGraph annotation will tell Hibernate to fetch the natures as well and then populates the entities with the natures. All this will be done automagically without any further ado.

And into your service goes this:

public List<Type> getAllComplaintTypesWithNatures() {
    List<Type> typeListWithNature = typeRepository.findAllWithNature();
    return typeListWithNature;
}

Also you may consider to use another keyword other than type, since this can lead to confusion or problems cause type is reserved in many languages.

As @Slevin said, it's a bad practice to use eager fetch type on entities, instead use @EntityGraph to fetch data eagerly when needed.

Additionally, to fetch only needed data I suggest you use projections. Projection can be class-based and interface-based. What's the difference? Class-based projections don't support nested data, whereas interface-based projections fetch all fields from the database and map the data programmatically in case of nested projections.

For example, when you need types without natures, you can define the following projection:

@Getter
@Setter
@AllArgsConstructor
public class TypeDto {

    private Long id;

    private String name;

}

Then, add the method below to the repository:

   List<TypeDto> findAllTypeDtosBy();

For more details about projections refer to the blog post.