使用 jackson 将 singleton json 数组反序列化为相同类型的 pojo？

Question

Is there any out of the box way to deserialize a singleton json array into a java pojo of the same type?

for example, I would like the following json:

[{"eventId": "event1", "timestamp": 1232432132}]

to be deserialized into the following java POJO:

class Event {
  String eventId;
  long timestamp;
}

I tried using the following class:

class Event {
  String eventId;
  long timestamp;

  public Event(@JsonProperty("eventId") String event, 
               @JsonProperty("timestamp") long timestamp)
    //fields init
  }

  @JsonCreator
  public Event(List<Event> singletonList)
    //take first element in list and set its fields on this
  } 

but this fails with: om.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize instance of java.util.ArrayList out of FIELD_NAME token

I know I can wrap the Event POJO with some other class like this:

class EventWrapper {
   Event event;

   @JsonCreator   
   EventWrapper(List<Event> events) {
     this.event = events.get(0);
   }  

but I would like to avoid that (as well as avoid custom deserializer)

Any help will be much appreciated.

Answer 1

you can get List by following this, instead of creating additional class,

    import com.fasterxml.jackson.databind.ObjectMapper;
    ObjectMapper mapper = new ObjectMapper();
    List<Event> myObjects = Arrays.asList(mapper.readValue(json, Event[].class));