java - JSON 在发布时递归调用对象

Question

我正在通过 Swagger 测试我的应用程序，当尝试发布一个包含其他对象列表的对象时，我收到错误 java.lang.StackOverflowError。基本上，我正在尝试编写一张发票，以 Swagger 形式表示为 JSON，在填写发票数据时，我注意到发票项目包含发票的重复字段。

{
  "date": "2017-08-27",
  "counterparty": {
    "address": {
      "houseNumber": "string",
      "streetName": "string",
      "townName": "string",
      "zipCode": "string"
    },
    "bankName": "string",
    "bankNumber": "string",
    "companyName": "string",
    "nip": "string",
    "phoneNumber": "string"
  },
  "invoiceItems": [
    {
      "amount": 0,
      "description": "string",
      "id": 0,
      "invoice": { //SHOULD NOT BE HERE
        "id": 0,
        "date": "2017-09-07",
        "counterparty": {
          "address": {
            "houseNumber": "string",
            "streetName": "string",
            "townName": "string",
            "zipCode": "string"
          },
          "bankName": "string",
          "bankNumber": "string",
          "companyName": "string",
          "nip": "string",
          "phoneNumber": "string"
        },
        "invoiceItems": [
          {}
        ]
      },
      "numberOfItems": 0,
      "vat": "VAT_23",
      "vatAmount": 0
    }
  ]
}

@Entity
@Table(name = "invoices")
public class Invoice implements Comparable<Invoice> {

      @Id
      @GeneratedValue(strategy = GenerationType.IDENTITY)
      @Column(name = "invoice_id")
      private int id;
      @Column(name = "date")
      private LocalDate date = LocalDate.now();
      @OneToOne(mappedBy = "invoice", cascade = {CascadeType.DETACH, CascadeType.MERGE,
          CascadeType.PERSIST, CascadeType.REFRESH})
      private Counterparty counterparty;

      @OneToMany(mappedBy = "invoice", cascade = {CascadeType.PERSIST, CascadeType.MERGE,
          CascadeType.DETACH, CascadeType.REFRESH})
      private List<InvoiceItem> invoiceItems = new ArrayList<>();

@Entity
@Table(name = "items")
public class InvoiceItem {

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "item_id")
  private int id;
  private String description;
  private int numberOfItems;
  private BigDecimal amount;
  private BigDecimal vatAmount;

  @JoinColumn(name = "vat_code")
  @Enumerated(EnumType.ORDINAL)
  private Vat vat;

  @ManyToOne(fetch = FetchType.LAZY, cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST,
      CascadeType.REFRESH})
  @JoinColumn(name = "invoice_id")
  private Invoice invoice;

我与 Counterparty 具有完全相同的映射，但它不显示 JSON 格式的发票数据:

@Id
  private String nip;
  private String companyName;
  private String phoneNumber;
  private String bankName;
  private String bankNumber;

  @OneToOne(fetch = FetchType.LAZY, mappedBy = "counterparty", cascade = CascadeType.ALL)
  private Address address;

  @ManyToOne(fetch = FetchType.LAZY, cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST,
      CascadeType.REFRESH})
  @JoinColumn(name = "invoice_id")
  private Invoice invoice;

也许我的注释存在一些问题，发票被递归调用？

Answer 1

您应该使用 @JsonIgnore 注释标记 InvoiceItems 上的 Invoice 属性，这意味着当 InvoiceItems 序列化时，它不会被序列化为 JSON，这应该可以防止无限递归 JSON 问题:

 @Entity
 @Table(name = "items")
 public class InvoiceItem {

 ...

     @ManyToOne(fetch = FetchType.LAZY, cascade = {CascadeType.DETACH, CascadeType.MERGE, CascadeType.PERSIST,
      CascadeType.REFRESH})
     @JoinColumn(name = "invoice_id")
     @JsonIgnore
     private Invoice invoice;