Question

我正在使用Spring框架创建一个简单的REST服务器。其中一个类需要自己加入一对多关系来检索有关它的父对象的数据。这堂课看起来像这样;

@Entity
@Table(name = "item", schema = "tmp", uniqueConstraints = {
    @UniqueConstraint(columnNames = "item_id"), @UniqueConstraint(columnNames = "item_name")})
public class Item implements Serializable {

  private static final long serialVersionUID = 1L;

  private Integer itemId;
  private String itemName;
  private String itemDescription;
  private Item itemParent;
  private boolean isEndItem;
  private List<Item> childrenItems;


  public Item() {}

  @Id
  @GeneratedValue(strategy = GenerationType.IDENTITY)
  @Column(name = "item_id", unique = true, nullable = false)
  public Integer getItemId() {
    return itemId;
  }

  public void setItemId(final Integer itemId) {
    this.itemId = itemId;
  }

  @Column(name = "item_name", unique = true, nullable = false)
  public String getItemName() {
    return itemName;
  }

  public void setItemName(final String itemName) {
    this.itemName = itemName;
  }

  @Column(name = "item_description", unique = false, nullable = false)
  public String getItemDescription() {
    return itemDescription;
  }

  public void setItemDescription(final String itemDescription) {
    this.itemDescription = itemDescription;
  }

  @ManyToOne(fetch = FetchType.LAZY, cascade = CascadeType.ALL)
  @JsonManagedReference(value = "item-item")
  @JoinColumn(name="item_parentid")
  public Item getParentItem() {
    return this.itemParent;
  }

  public void setParentItem(final Item itemParent){
    this.itemParent = itemParent;
  }

  @OneToMany(mappedBy="childrenItems", fetch = FetchType.LAZY, cascade = CascadeType.ALL)
  @JsonBackReference(value = "item-item")
  public List<Item> getChildrenItems(){
    return this.childrenItems;
  }

  public void setChildrenItems(final List<Item> childrenItems){
    this.childrenItems = childrenItems;
  }

  @Column(name = "item_isendproduct", unique = false, nullable = false)
  public boolean isEndItem() {
    return isEndItem;
  }

  public void setEndItem(final boolean isEndItem) {
    this.isEndItem = isEndItem;
  }
}

在我的数据库中，测试数据保存在此层次结构中：

条目＆gt;沙拉＆gt; House Salad

[  
   {  
      "itemId":1,
      "itemName":"Entry",
      "itemDescription":"Entry Menu",
      "endItem":false,
      "parentItem":null
   },
   {  
      "itemId":2,
      "itemName":"Salad",
      "itemDescription":"Salad Menu",
      "endItem":false,
      "parentItem":{  
         "itemId":1,
         "itemName":"Entry",
         "itemDescription":"Entry Menu",
         "endItem":false,
         "parentItem":null
      }
   },
   {  
      "itemId":3,
      "itemName":"House Salad",
      "itemDescription":"House Salad",
      "endItem":true,
      "parentItem":{  
         "itemId":2,
         "itemName":"Salad",
         "itemDescription":"Salad Menu",
         "endItem":false,
         "parentItem":{  
            "itemId":1,
            "itemName":"Entry",
            "itemDescription":"Entry Menu",
            "endItem":false,
            "parentItem":null
         }
      }
   }
]

但我不想知道有关父母对象的信息。是否有任何注释可用于实现此目的？

提前感谢

无论如何在JPA中检索子项的直接父项？

0 个答案: