java - Jackson 的 @JsonPropertyOrder 不适用于 @JsonUnwrapped

Question

我有一个对象，其中包含另一个对象属性，如下所示:

import com.fasterxml.jackson.annotation.JsonPropertyOrder;
import com.fasterxml.jackson.annotation.JsonUnwrapped;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import lombok.Data;

@JsonPropertyOrder({"fA1","b","fA2"})
@Data
public class A {
    private String fA1;
    private String fA2;

    @JsonUnwrapped
    private B b = new B();

    @Data
    class B {
        private String fB1;
        private String fB2;
    }

    public static void main(String[] args) throws JsonProcessingException {
        ObjectMapper objectMapper = new ObjectMapper();
        A a = new A ();
        System.out.println(objectMapper.writeValueAsString(a));
    }

}

我想要的是生成尊重这个顺序的json:

{
  "fA1":"",
  "fB1":"",
  "fA2":"",
  "fB2":""
}

有什么办法可以做到这一点吗？

Answer 1

根据this issue在 GitHub 上的 jackson-databind 存储库中，@JsonPropertyOrder注释不适用于 @JsonUnwrapped注解。请参阅下面的引用:

True, unwrapped properties are not included in ordering, since they are not really known by enclosing serializer as regular properties. And specifically, as things are, will be output as a block of properties per contained, so even if known they can not be reordered separately.

Perhaps something could be done with Jackson 3.x once we get there.

<小时/>

但是您可以考虑一个解决方法:由于您似乎正在使用 Lombok，因此您可以使用 @Delegate 注释 b和 @JsonIgnore :

@Data
@JsonPropertyOrder({"fa1", "fb1", "fa2", "fb2"})
public class A {

    private String fA1;
    private String fA2;

    @Delegate
    @JsonIgnore
    private B b = new B();
}

@JsonIgnore注释将确保 b 属性不会被 Jackson 序列化。

还有@Delegate注解将告诉 Lombok 生成委托(delegate)方法，将调用转发给 B 方法。这样，A 类将具有被委托(delegate)给 fB1 和 fB2 字段的 getter 和 setter 的 getter 和 setter。