I'm using SpringBoot and JPA to build a REST interface.
Now, I have a strange JSON returned for the list of products fetched from the database. Let's say that I have:
@Entity
public class Product {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@ManyToOne(optional = false, fetch = FetchType.LAZY)
@JoinColumn(name = "categoryId", nullable = false, updatable = false)
private Category category;
...
}
@Entity
public class Category implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
@OneToMany(mappedBy = "category", cascade = CascadeType.DETACH)
@OrderBy("name ASC")
private List<Product> products = Collections.emptyList();
...
}
The JPA repository for the Product
is defined as:
public interface ProductRepository extends JpaRepository<Product, Long> {
List<Product> findAll();
}
In my controller I have:
@Autowired
private ProductRepository productRepo;
@RequestMapping("/all-products", method = RequestMethod.GET)
public Map<String,Object> home() {
Map<String,Object> model = new HashMap<String,Object>();
model.put("products", productRepo.findAll());
return model;
}
What is driving my crazy, is that if I try to call this service as follows:
$ curl localhost:8080/all-products
I get a recursive output due to the relationship between tables product
and category
, e.g.:
{"products":[{"id":1,"name":"Product1","category":
{"id":1,"name":"Cat1","products":[{"id":6,"name":"Product6","category":
{"id":1,"name":"Cat1","products":[{"id":6,"name":"Product6","category":
{"id":1,...
What am I doing wrong?
You're not doing anything wrong (at least at the code level it's rather conceptual) - json serializer just goes like this:
You must use a view or just skip it.
Use @JsonView
Use a view as a POJO
Return new ProductView
that has all fields of product and a reference (category) to new CategoryView
(you can end at this point) that has collection of (products) new ProductViewWithoutReferences
, and so on
Use @JsonIgnore
on a collection of products
And as a side note - if it's a @RestController
and you're invoking "all-products" then it's a bit unusual to return something else than a list. Wrapping the response in a map is redundant. Many rest clients expect a list when they invoke list()
method.
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