CODEWITHSUNDEEP
javajsonjacksonjson-deserialization
VB_
VB_

Reputation: 45722

JSON: JsonMappingException while try to deserialize object with null values

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

Upvotes: 28

Views: 105410

Answers (4)

Shankar Murthy
Shankar Murthy

Reputation: 150

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

@JsonProperty
private String id;

Upvotes: 0

Abhiroop Nandi Ray
Abhiroop Nandi Ray

Reputation: 397

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;
}
}

Upvotes: 2

Neman
Neman

Reputation: 1307

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);

Upvotes: 57

Vinod
Vinod

Reputation: 1130

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?

Upvotes: 22

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