假设我们有这样的课程：

public class Cart{
   private int id;
   private String cartName;
   private String color;
   @JsonIgnore
   @OneToMany(mappedBy = "cart")
   private List<Item> items;
}

public class Item{
   @ManyToOne
   @JoinColumn(nullable = false)
   private Cart cart;
   private int id;
   private String itemName;
   private double weight;
}

通常，序列化item类时会看到：

{ 
   "id" : 1,
   "itemName" : "NiceItem",
   "weight" : 5.2,
   "cart" : {
      "id" : 3,
      "cartName" : "NiceCart",
      "color" : "Red"
   }
}

我的问题是如何使cart按其id序列化，如下所示：

{ 
   "id" : 1,
   "itemName" : "NiceItem",
   "weight" : 5.2,
   "cart_id" : 3
}