Sping boot多对多GET请求

Question

我的Spring启动应用程序中有多对多关系。但是当我尝试获取响应时，我总是得到一个空数组；下面是我的类(我粘贴了没有构造函数、getter和setter的代码，但我在代码中有它们)：

@Entity
@Table(name="orders")
public class Order {
    private @Id
    @GeneratedValue
    Long id;
    @OneToOne(cascade = CascadeType.ALL)
    private Customer customer;
    @OneToMany(mappedBy = "product",fetch = FetchType.LAZY,cascade = {CascadeType.PERSIST,CascadeType.MERGE,CascadeType.DETACH},orphanRemoval = true)
    private Set<ProductOrderDetails> productOrderDetails;
    @DateTimeFormat
    private Date shippmentDate;
    private double totalOrderPrice;
    private OrderStatus status;
    private String note1;
    private String note2;

@Entity
@Table
public class Product {
    private @Id
    @GeneratedValue
    Long id;
    private String name;
    private String model;
    private String color;
    private String material;
    private double price;
    @Transient
    private int productQuantity;
    @OneToMany(mappedBy = "order",fetch = FetchType.LAZY)
    private List<ProductOrderDetails> productOrderDetailsSet;

@Entity
@IdClass(ProductOrderDetails.class)
public class ProductOrderDetails implements Serializable {

    @Id
    @ManyToOne(cascade = CascadeType.ALL)
    @JoinColumn(name="order_id")
    Order order;

    @Id
    @ManyToOne(cascade = {CascadeType.PERSIST,CascadeType.MERGE,CascadeType.DETACH})
    @JoinColumn(name="product_id")
    Product product;

    private int quantity;

下面是我的OrderController代码：

@GetMapping("/{id}")
    public Order One(@PathVariable Long id) {
        Order order=repository.findById(id).orElseThrow(()->new ObjectNotFoundException(id));
      return order;
    }

这是我得到的回应：

{
    "id": 2,
    "customer": {
        "id": 1,
        "name": "Company",
        "address": "Main Street 1",
        "city": "Bern",
        "state": "Switzerland",
        "zip": 58529,
        "contactPersonName": "John Smith",
        "contactPersonEmail": "test@gmail.com"
    },
    "productOrderDetails": [],
    "shippmentDate": "2020-12-09T23:00:00.000+00:00",
    "totalOrderPrice": 3434.0,
    "status": "WAITING",
    "note1": "note 1",
    "note2": "note 2"
}

如何获取productOrderDetails数组(已订购的产品数组)？如果我可以使用JPA，我会更喜欢

Answer 1

您有几种方法可以做到这一点：

• Using FetchType.EAGER strategy

@Entity
@Table(name="orders")
public class Order {
    private @Id
    @GeneratedValue
    Long id;
    @OneToOne(cascade = CascadeType.ALL)
    private Customer customer;
    @OneToMany(mappedBy = "product",fetch = FetchType.EAGER,cascade = {CascadeType.PERSIST,CascadeType.MERGE,CascadeType.DETACH},orphanRemoval = true)
    private Set<ProductOrderDetails> productOrderDetails;
    @DateTimeFormat
    private Date shippmentDate;
    private double totalOrderPrice;
    private OrderStatus status;
    private String note1;
    private String note2;
}

在自定义存储库方法中使用联接获取的

• ：

@Query(value = "SELECT o FROM Order o JOIN FETCH o.productOrderDetails")
List<Order> findAllOrders();

Answer 2

所以对于任何和我有同样问题的人来说，我有一个拼写错误，在我应该使用的Order类中：

  @OneToMany(mappedBy = "order",fetch = FetchType.LAZY,cascade = {CascadeType.PERSIST,CascadeType.MERGE,CascadeType.DETACH},orphanRemoval = true)
    private Set<ProductOrderDetails> productOrderDetails;

而不是mappedBy=的“产品”。如果你不想在GET请求时进行递归调用，你应该在ProductOrderDetails类中添加@JsonIgnore：

@Id
@ManyToOne(cascade = CascadeType.ALL)
@JoinColumn(name="order_id")
@JsonIgnore
Order order;

代码的其余部分保持不变。