JSON: JsonMappingException while try to deserialize object with null values

Question

I try to deserialize object that contains null-properties and have the JsonMappingException.

What I do:

String actual = "{\"@class\" : \"PersonResponse\"," +
                "  \"id\" : \"PersonResponse\"," +
                "  \"result\" : \"Ok\"," +
                "  \"message\" : \"Send new person object to the client\"," +
                "  \"person\" : {" +
                "    \"id\" : 51," +
                "    \"firstName\" : null}}";
ObjectMapper mapper = new ObjectMapper();
mapper.readValue(new StringReader(json), PersonResponse.class); //EXCEPTION!

BUT: if to throw away "firstName = null" property - all works fine! I mean pass the next string:

String test = "{\"@class\" : \"PersonResponse\"," +
                "  \"id\" : \"PersonResponse\"," +
                "  \"result\" : \"Ok\"," +
                "  \"message\" : \"Send new person object to the client\"," +
                "  \"person\" : {" +
                "    \"id\" : 51}}";
ObjectMapper mapper = new ObjectMapper();
mapper.readValue(new StringReader(json), PersonResponse.class); //ALL WORKS FINE!

Question: How to avoid this exception or to pledge Jackson ignore null-values during serialization?

Throws:

Message:

com.fasterxml.jackson.databind.MessageJsonException:
 com.fasterxml.jackson.databind.JsonMappingException:
  N/A (through reference chain: person.Create["person"]->Person["firstName"])

cause:

com.fasterxml.jackson.databind.MessageJsonException:
 com.fasterxml.jackson.databind.JsonMappingException:
  N/A (through reference chain: prson.Create["person"]->Person["firstName"])

cause: java.lang.NullPointerException

Neman · Accepted Answer · 2015-06-04 13:01:40Z

58

Sometimes this problem occurs when accidentally using a primitive type as return type of the getter of a non-primitive field:

public class Item
{
    private Float value;

    public float getValue()
    {
        return value;
    }

    public void setValue(Float value)
    {
        this.value = value;
    }   
}

Notice the "float" instead of "Float" for the getValue()-method, this can lead to a Null Pointer Exception, even when you have added

objectMapper.setSerializationInclusion(Include.NON_NULL);

answered Jun 4, 2015 at 13:01

Neman

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7 Comments

StaxMan Over a year ago

Yes. And note that this is because of implicit coercion in getValue(), which is basically doing "return value.floatValue()" to get primitive -- hence NPE. Caller has no way of avoiding that, or knowing there is such a problem (unless it went and decoded bytecode etc).

VeenarM Over a year ago

You sir saved my day :) I had a Boolean value, but accidently in the getter had it as a boolean and it was null :D

Jelle den Burger Over a year ago

This was it. I also had a Boolean and a method boolean get...().

Rami Muurimäki Over a year ago

And my issue was that the getter / setter was had a typo. After I recreated the getters and setters using Eclipse's tools, everything works

LALIT JAMNAL Over a year ago

you are a savior. I was debugging it and analysing like a big issue and this was a simple mistake on my side. thanks so much :)

|

Vinod · Accepted Answer · 2013-08-07 07:10:46Z

22

If you don't want to serialize null values, you can use the following setting (during serialization):

objectMapper.setSerializationInclusion(Include.NON_NULL);

Hope this solves your problem.

But the NullPointerException you get during deserialization seems suspicious to me (Jackson should ideally be able to handle null values in the serialized output). Could you post the code corresponding to the PersonResponse class?

edited Aug 7, 2013 at 7:10

answered Aug 7, 2013 at 7:03

Vinod

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3 Comments

VB_ Over a year ago

hah. I also have collections in my person-class, so I need to set Include.NOT_EMPTY. Thanks!!!

Eric Huang Over a year ago

Where should I put the objectMapper? within controller? or in the POJO bean? thanks....

nitinsridar Over a year ago

It's NON_EMPTY not NOT_EMPTY

Abhiroop Nandi Ray · Accepted Answer · 2018-09-06 08:26:18Z

3

I also faced the same issue.

I just included a default constructor in the model class along with the other constructor with parameters.

It worked.

package objmodel;

import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;

public class CarModel {

private String company;
private String model;
private String color;
private String power;


public CarModel() {
}

public CarModel(String company, String model, String color, String power) {
    this.company = company;
    this.model = model;
    this.color = color;
    this.power = power;

}

@JsonDeserialize
public String getCompany() {
    return company;
}

public void setCompany(String company) {
    this.company = company;
}

@JsonDeserialize
public String getModel() {
    return model;
}

public void setModel(String model) {
    this.model = model;
}

@JsonDeserialize
public String getColor() {
    return color;
}

public void setColor(String color) {
    this.color = color;
}

@JsonDeserialize
public String getPower() {
    return power;
}

public void setPower(String power) {
    this.power = power;
}
}

answered Sep 6, 2018 at 8:26

Abhiroop Nandi Ray

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2 Comments

Abhiroop Nandi Ray Over a year ago

I also tried removing the annotations "@JsonDeserialize" and also removing the line objectmapper.setSerializationInclusion(JsonInclude.Include.NON_NULL); It worked fine!!

Raj Rajeshwar Singh Rathore Over a year ago

Had to add super() in the default constructor to make it work.

Shankar Murthy · Accepted Answer · 2019-01-30 13:44:22Z

0

Add JsonProperty annotation to your attribute in TO class, as below

@JsonProperty
private String id;

answered Jan 30, 2019 at 13:44

Shankar Murthy

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