Spring-Data-Jpa 中一对多映射的 JSON 结果错误

Posted 2023-02-26

【中文标题】Spring-Data-Jpa 中一对多映射的 JSON 结果错误

【英文标题】：Error in JSON result for one to many mapping in Spring-Data-Jpa

【发布时间】：2019-03-27 19:50:21

【问题描述】：

所有者实体：PriceListItemTest.java

@JsonPropertyOrder("pricingUOMCode","lineTypeCode","primaryPricingUOMFlag","priceListId","itemId","priceListItemId")
@Entity
@Table(name = "QP_PRICE_LIST_ITEMS")
public class PriceListItemTest implements Serializable

    @Column(name = "price_list_item_id")    
    private String priceListItemId;

    @Column(name = "pricing_uom_code")  
    private String pricingUOMCode; 

    @Column(name = "line_type_code")    
    private String lineTypeCode; 

    @Column(name = "primary_pricing_uom_flag")  
    private String primaryPricingUOMFlag;

    @Id
    @Column(name = "item_id")   
    private String itemId;

    @OneToMany(mappedBy = "priceListItemsTest", cascade = CascadeType.ALL)
    private List<ItemDetailTest> itemDetailsTest;

    // getters and setters

和Entity2：ItemDetailTest.java

@JsonPropertyOrder("itemNumber","inventoryItemId","organizationId")
@Entity
@Table(name = "egp_system_items_b")
public class ItemDetailTest implements Serializable 

    @Id
    @Column(name = "inventory_item_id") 
    private String inventoryItemId; 

    @Column(name = "item_number")   
    private String itemNumber; 

    @Column(name = "organization_id")   
    private String organizationId;


//   To be used for bidirectional   
    @ManyToOne//(fetch = FetchType.LAZY)
    private PriceListItemTest priceListItemsTest;

    // getters and setters

RestController 在检索 JSON 结果时返回错误。

    "timestamp": "2018-10-23T14:05:26.248+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "Could not write JSON: could not extract ResultSet; nested exception is com.fasterxml.jackson.databind.JsonMappingException: could not extract ResultSet (through reference chain: java.util.ArrayList[0]->com.Pricing.Pricing_App.model.PriceListItemTest[\"itemDetailsTest\"])",
    "path": "/getByItemIdTest"

可能是映射 oneTomany 是错误的。 如果它具有 oneToone 映射但面临 OneToMany 问题，则它工作正常。 有人可以帮我解决错误吗？

编辑： 控制器：

@RestController
public class PriceListItemControllerTest 

    @Autowired
    private PriceListItemRepositoryTest priceListItemRepositoryTest;

    @GetMapping(value="/getByItemIdTest")
    public List<PriceListItemTest> getByItemIdTest(@RequestParam("itemId") String itemId) 
        return priceListItemRepositoryTest.findByItemId(itemId);
    

【问题讨论】：

如果您可以发布您的 REST 控制器和 API 请求以及日志，这将对我们更有帮助。

我已经添加了 Rest Controller

【参考方案1】：

使用@JsonIgnore，如下所示。问题是无限的 json 调用正在通过你的 json 调用。忽略在您的 ManytoOne 关系上使用此注释。对我来说很好。

@ManyToOne//(fetch = FetchType.LAZY)
@JsonIgnore
private PriceListItemTest priceListItemsTest;

【参考方案2】：

如下更改您的模型类：

@Entity
@Table(name = "QP_PRICE_LIST_ITEMS")
public class PriceListItemTest implements Serializable 

    private static final long serialVersionUID = -748956247024967638L;

    @Basic
    @Column(name = "price_list_item_id")    
    private String priceListItemId;

    @Basic
    @Column(name = "pricing_uom_code")  
    private String pricingUOMCode; 

    @Basic
    @Column(name = "line_type_code")    
    private String lineTypeCode; 

    @Basic
    @Column(name = "primary_pricing_uom_flag")  
    private String primaryPricingUOMFlag;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "item_id")   
    private String itemId;

    @JsonManagedReference
    @OneToMany(mappedBy = "priceListItemsTest", cascade = CascadeType.ALL)
    private List<ItemDetailTest> itemDetailsTest;

    // getters and setters

和

@Entity
@Table(name = "egp_system_items_b")
public class ItemDetailTest implements Serializable 

    private static final long serialVersionUID = 8495817802073010928L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "inventory_item_id") 
    private String inventoryItemId; 

    @Basic
    @Column(name = "item_number")   
    private String itemNumber; 

    @Basic
    @Column(name = "organization_id")   
    private String organizationId;

    @JsonBackReference
    @ManyToOne
    @JoinColumn(name = "fk_item_id", nullable = false) // name of the foreign key column
    private PriceListItemTest priceListItemsTest;

    // getters and setters

在您的 JoinColumn 中提供外键字段的实际名称。它应该可以工作，因为 Jackson 会自动序列化。

对于一对多的引用，您可以点击以下链接：link1 和 link2

【参考方案3】：

两个实体之间存在双向映射，这会在 JSON 序列化期间导致无限循环。

例如，您必须使用 @JsonIgnore 忽略其中一侧。

在此处阅读有关该主题的更多信息：

https://www.baeldung.com/jackson-bidirectional-relationships-and-infinite-recursion