Java Jackson将子类型集枚举字段反序列化为null

更新：删除多余代码

我需要反序列化一个JSON对象，它可以是父类的许多子类型之一。它是哪个特定子类型由对象中的特定枚举字段确定。我已经向父类添加了

@JsonTypeInfo

和

@JsonSubTypes

注释，据我所知，它们都是正确的

但是，枚举值与Java类中的枚举名称不完全相同。因此，在enum类中，我用

@JsonCreator

注释了一个静态方法，这样Jackson知道如何将值反序列化到一个正确的Java enum

我遇到的问题是，一旦我反序列化了JSON字符串，保存枚举的字段就不包含实际的枚举值-它被保留为

null

为什么

day

字段保留为

null

，在反序列化过程中如何将其设置为预期值

代码如下

父日历类

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "day")
// For the sake of correct deserialisation, we need to map from values of type to child model classes explicitly
@JsonSubTypes({ @JsonSubTypes.Type(value = Monday.class, name = "monday"),
   @JsonSubTypes.Type(value = Monday.class, name = "mon"),
   @JsonSubTypes.Type(value = Tuesday.class, name = "tuesday"),
   @JsonSubTypes.Type(value = Tuesday.class, name = "tues")})
public class Calendar {
   protected String calendarName;
   protected DaysOfWeek day;

   @JsonProperty("calendarName")
   public String getCalendarName() {
      return calendarName;
   }

   public void setCalendarName(String calendarName) {
      this.calendarName = calendarName;
   }

   @JsonProperty("day")
   public DaysOfWeek getDay() {
      return day;
   }

   public void setDay(DaysOfWeek day) {
      this.day = day;
   }
}

儿童课程周一和周二 星期一

星期二

public class Tuesday extends Calendar {
   private Meetings object;

   public Tuesday() {
   }

   public Tuesday(Meetings object) {
      this.object = object;
   }

   @JsonProperty("object")
   public Meetings getObject() {
      return object;
   }

   public void setObject(Meetings object) {
      this.object = object;
   }
}

DaysOfWeek枚举类

public enum DaysOfWeek {
   MONDAY("monday"),
   MON("mon"),
   TUESDAY("tuesday"),
   TUES("tues");

   private String value;

   DaysOfWeek(String value) {
      this.value = value;
   }

   @Override
   @JsonValue
   public String toString() {
      return String.valueOf(value);
   }

   @JsonCreator
   public static DaysOfWeek fromEventString(@JsonProperty("value") String eventString) {
      return Arrays.stream(DaysOfWeek.values()).filter(e -> e.value.equals(eventString)).findFirst().get();
   }
}

JSON源字符串

{
  "calendarName":"My Tuesdays",
  "day":"tuesday",
  "object":{
    "meetings":[
      "team",
      "company",
      "client"]
  }
}

反序列化对象（从上面的字符串反序列化）

---

通过同事找到答案

我需要将

@JsonTypeInfo

注释的

visible

属性设置为

true

：

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "day", visible = true)
// For the sake of correct deserialisation, we need to map from values of type to child model classes explicitly
@JsonSubTypes({ @JsonSubTypes.Type(value = Monday.class, name = "monday"),
   @JsonSubTypes.Type(value = Monday.class, name = "mon"),
   @JsonSubTypes.Type(value = Tuesday.class, name = "tuesday"),
   @JsonSubTypes.Type(value = Tuesday.class, name = "tues")})
public class Calendar {
...

---

这是很多代码。请回答您的问题并删除所有不需要重新解决问题的内容。Calendar类的第一个中有两个同名的“day”属性，@JsonTypeInfo中有一个同名的属性。

@JsonTypeInfo

中的

day

属性不是指

Calendar

类中的

day

字段吗？或者你是说我复制了那个字段？星期一和星期一有什么区别？一个类有两个不同的

类型
标识符有意义吗？
Tuesday {
  object=Meetings {
  meetings=[team, company, client]
},
  calendarName=My Tuesdays,
  day=null //I want this to be "tuesday", not null
}

@JsonTypeInfo(use = JsonTypeInfo.Id.NAME, include = JsonTypeInfo.As.EXISTING_PROPERTY, property = "day", visible = true)
// For the sake of correct deserialisation, we need to map from values of type to child model classes explicitly
@JsonSubTypes({ @JsonSubTypes.Type(value = Monday.class, name = "monday"),
   @JsonSubTypes.Type(value = Monday.class, name = "mon"),
   @JsonSubTypes.Type(value = Tuesday.class, name = "tuesday"),
   @JsonSubTypes.Type(value = Tuesday.class, name = "tues")})
public class Calendar {
...