java - Spring boot一对多连接从数据库获取重复的json

Question

产品.java

@Entity @Table(name="product") public class Product {
          // ...
          @ManyToOne @JoinColumn(name="product_id")
          private Brand brand;
          // getters and setters
}

品牌.java

@Entity @Table(name="brand") public class Brand {
          // ....
          @OneToMany(mappedBy="brand", cascade = CascadeType.ALL)
          private Set<Product> products;
}

BrandRepository.java

@Repository public interface BrandRepository extends JpaRepository<Brand, Long>{}

BrandController.java

@RestController @RequestMapping("/api/v1")
public class BrandController {
          @Autowired private BrandRepository brandRepository;

          @GetMapping("/brands")
          public List<Brand> getAllBrands(){
                    return brandRepository.findAll();
          }
          @GetMapping("/brand/{id}")
          public ResponseEntity<Brand> getBrand(@PathVariable(value="id") Long bid) throws ResourceNotFoundException {
                    Brand brand = brandRepository.findById(bid).orElseThrow(() -> new ResourceNotFoundException("user not found"+bid));
                    return ResponseEntity.ok().body(brand);
          }
}

每当我尝试访问/brands 或/brand/1 时，我都会收到如下重复的 json 结果:

对于“http://127.0.0.1:8080/api/v1/brands”

[{"id":1,"name":"Apple","products":[{"id":4,"name":"Apple kndsksk ksjdsoijd sd","price":"2893787","brand":{"id":1,"name":"Apple","products":[{"id":4,"name":"Apple kndsksk ksjdsoijd sd","price":"2893787","brand":{"id":1,"name":"Apple","products":[{"id":4,"name":"Apple kndsksk ksjdsoijd sd","price":"2893787","brand":{"id":1,"name":"Apple","products":[{"id":4,"name":"Apple 
... and continues

对于“http://127.0.0.1:8080/api/v1/brand/1”

{"id":1,"name":"Apple","products":[{"id":1,"name":"Apple kksf sfok sokoak","price":"9239932","brand":{"id":1,"name":"Apple","products":[{"id":1,"name":"Apple kksf sfok sokoak","price":"9239932","brand":{"id":1,"name":"Apple","products":[{"id":1,"name":"Apple kksf sfok sokoak","price":"9239932","brand":{"id":1,"name":"Apple","products":[{"id":1,"name":"Apple kksf sfok sokoak","price":"9239932","brand":{"id":1,"name":"Apple","products":[{"id":1,"name":"Apple kksf sfok sokoak","price":"9239932","brand":{"id":1,"name":"Apple","products":[{"id":1,"name":"Apple kks 
... and continues

Answer 1

您可以使用@JsonIgnore注释来抑制这种无限循环。例如:

@JsonIgnore
@ManyToOne @JoinColumn(name="product_id")
private Brand brand;