java - Hibernate省略了JsonManagedReference来保持

我试图保留一个具有内部列表的对象。
我必须使用@JsonManagedReference注释实体Item
和ItemProperty和@JsonBackReference，以避免无限循环-中断循环。

对于获取具有项目属性的项目，这很好。现在的问题是，当我尝试使用项目属性列表持久化新项目时，仅持久化了该项目，而没有任何ItemProperties。有人知道为什么吗？ @ JsonBackReference / ManagedReference注释是否带有某些注释？

码：

import com.fasterxml.jackson.annotation.JsonManagedReference;
import javax.persistence.*;
import java.util.List;
import java.util.Objects;

@Entity
@Table(name = "item")
public class Item {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;

@Enumerated(EnumType.STRING)
@Column(name = "type")
private ItemType itemType;

@OneToMany(mappedBy = "item")
// @JsonManagedReference is the forward part of reference which gets serialized normally.
@JsonManagedReference
private List<ItemProperty> itemProperties;

public Item() {

}

public Item(ItemType itemType, List<ItemProperty> itemProperties) {
    this.itemType = itemType;
    this.itemProperties = itemProperties;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public ItemType getItemType() {
    return itemType;
}

public void setItemType(ItemType itemType) {
    this.itemType = itemType;
}

public List<ItemProperty> getItemProperties() {
    return itemProperties;
}

public void setItemProperties(List<ItemProperty> itemProperties) {
    this.itemProperties = itemProperties;
}

@Override
public String toString() {
    return "Item{" +
            "id=" + id +
            ", itemType=" + itemType +
            ", itemProperties=" + itemProperties +
            '}';
}

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    Item item = (Item) o;
    return id == item.id &&
            itemType == item.itemType &&
            Objects.equals(itemProperties, item.itemProperties);
}

@Override
public int hashCode() {
    return Objects.hash(id, itemType, itemProperties);
}
}

项目属性：

import com.fasterxml.jackson.annotation.JsonBackReference;

import javax.persistence.*;
import java.util.Objects;

@Entity
@Table(name = "item_properties")
public class ItemProperty {

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "id")
private int id;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "item_id")
@JsonBackReference
private Item item;

@ManyToOne(fetch = FetchType.EAGER)
@JoinColumn(name = "item_property_definition_id")
private ItemPropertyDefinition itemPropertyDefinition;

@Column(name = "value")
private String value;

public ItemProperty(){}

public ItemProperty(Item item, ItemPropertyDefinition itemPropertyDefinition, String value) {
    this.item = item;
    this.itemPropertyDefinition = itemPropertyDefinition;
    this.value = value;
}

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

public Item getItem() {
    return item;
}

public void setItem(Item item) {
    this.item = item;
}

public ItemPropertyDefinition getItemPropertyDefinition() {
    return itemPropertyDefinition;
}

public void setItemPropertyDefinition(ItemPropertyDefinition itemPropertyDefinition) {
    this.itemPropertyDefinition = itemPropertyDefinition;
}

public String getValue() {
    return value;
}

public void setValue(String value) {
    this.value = value;
}

@Override
public String toString() {
    return "ItemProperty{" +
            "id=" + id +
            ", item=" + item +
            ", itemPropertyDefinition=" + itemPropertyDefinition +
            ", value='" + value + '\'' +
            '}';
}

@Override
public boolean equals(Object o) {
    if (this == o) return true;
    if (o == null || getClass() != o.getClass()) return false;
    ItemProperty that = (ItemProperty) o;
    return id == that.id &&
            Objects.equals(item, that.item) &&
            Objects.equals(itemPropertyDefinition, that.itemPropertyDefinition) &&
            Objects.equals(value, that.value);
}

@Override
public int hashCode() {
    return Objects.hash(id, item, itemPropertyDefinition, value);
}

}

在REST控制器中：

   @PostMapping("/items")
Item addItem(@RequestBody Item item) {
    item.setId(0);
    return this.itemService.addItem(item);
}

在此先感谢您的提示。

祝您有美好的一天，并祝您编程愉快！

最佳答案

您尚未在@OneToMany中声明级联标志。默认情况下，对项目实体的任何操作都不会级联到ItemProperty列表。因此，请看一下CascadeType枚举，并将要级联的操作设置为itemsproperty列表。有关CascadeTypes的更多信息，请参见here。

例：

@OneToMany(cascade = CascadeType.ALL, mappedBy = "item", orphanRemoval = true)
// @JsonManagedReference is the forward part of reference which gets serialized normally.
@JsonManagedReference
private List<ItemProperty> itemProperties;

如果您想知道orphanRemoval有什么用，请查看此question。