从ObjectMapper中的POJO重写@JsonInclude(ObjectMapper)

Question

问题：是否可以在创建POJO时覆盖POJO中定义的Include.NON_NULL

解释：

假设我有一个POJO，如下所示：

@JsonInclude(Include.NON_NULL)
class POJO {
  String name;
  String description;
  //Constructors, Getters & Setters, etc
}

以及下面的测试类：

class Main {
  public static void main(String args[]) {
    POJO p = new POJO();
    ObjectMapper mapper = new ObjectMapper();
     String jsonString = mapper.setSerializationInclusion(Include.ALWAYS)
                               .writerWithDefaultPrettyPrinter()
                               .writeValueAsString(p);
    //jsonString should contain empty name & description fields, but they doesn't
  }
}

Answer 1

您可以使用混合方式，因为它比注释具有优先级。

@JsonInclude(JsonInclude.Include.ALWAYS)
public class MixIn {
}

然后把它加到地图上

ObjectMapper mapper = new ObjectMapper();
mapper.addMixIn(POJO.class, MixIn.class);

结果将是

{"name":null,"description":null}