How to tell Jackson to ignore empty object during deserialization?

Question

At the deserialization process (which as I understand is the process of converting JSON data into a Java Object), how can I tell Jackson that when it reads a object that con

Answer 1

I would use a JsonDeserializer. Inspect the field in question, determine, if it is emtpy and return null, so your ContainedObject would be null.

Something like this (semi-pseudo):

 public class MyDes extends JsonDeserializer<ContainedObject> {

        @Override
        public String deserialize(JsonParser jsonParser, DeserializationContext context) throws IOException, JsonProcessingException {
            //read the JsonNode and determine if it is empty JSON object
            //and if so return null

            if (node is empty....) {
                return null;
            }
            return node;
        }

    }

then in your model:

 public class Entity {
    private long id;
    private String description;

    @JsonDeserialize(using = MyDes.class)
    private ContainedObject containedObject;

   //Contructor, getters and setters omitted

 }

Hope this helps!

Answer 2

You can implement a custom deserializer as follows:

public class Entity {
    private long id;
    private String description;
    @JsonDeserialize(using = EmptyToNullObject.class)
    private ContainedObject containedObject;

//Contructor, getters and setters omitted

}


public class EmptyToNullObject extends JsonDeserializer<ContainedObject> {

  public ContainedObject deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
    JsonNode node = jp.getCodec().readTree(jp);
    long contObjId = (Long) ((LongNode) node.get("contObjId")).numberValue();
    String aString = node.get("aString").asText();
    if(aString.equals("") && contObjId == 0L) {
      return null;
    } else {
      return new ContainedObject(contObjId, aString);
    }

  }
}

Answer 3

Approach 1 : This is mostly used. @JsonInclude is used to exclude properties with empty/null/default values.Use @JsonInclude(JsonInclude.Include.NON_NULL) or @JsonInclude(JsonInclude.Include.NON_EMPTY) as per your requirement.

    @JsonInclude(JsonInclude.Include.NON_NULL)
    public class Employee {

        private String empId;
        private String firstName;

        @JsonInclude(JsonInclude.Include.NON_NULL)
        private String lastName;
        private String address;
        private String emailId;

   }

More info about the jackson annotations : https://github.com/FasterXML/jackson-annotations/wiki/Jackson-Annotations

Approach 2 : GSON

use GSON (https://code.google.com/p/google-gson/)