Ignore null fields when DEserializing JSON with Gson or Jackson

Question

I know there's lots of questions about skipping fields with a null value when serializing objects to JSON. I want to skip / ignore fields with null values when deserializing JSON to an object.

Consider the class

public class User {
    Long id = 42L;
    String name = "John";
}

and the JSON string

{"id":1,"name":null}

When doing

User user = gson.fromJson(json, User.class)

I want user.id to be '1' and user.name to be 'John'.

Is this possible with either Gson or Jackson in a general fashion (without special TypeAdapters or similar)?

How will user.name be 'John'. if the example json has "name":null ? Are you asking if it can skip Null values in Json and not override the default in the class? — jeff porter, Apr 06 '16 at 13:34

score 4 · Answer 1 · answered Jan 11 '22 at 15:11

4

A lot of time gone by, but if you like me ran into this question and you are using at least Jackson 2.9 then one way you could sovle it is using JsonSetter and Nulls.SKIP:

public class User {
    private Long id = 42L;
    
    @JsonSetter(Nulls.SKIP)
    private String name = "John";

    ... cooresponding getters and setters  
   
}

This way, when null is encountered, setter will not be called.

Note: more details can be found here.

answered Jan 11 '22 at 15:11

Vytautas Alkimavičius

554
5
8

1

This code actually does not compile. The JsonSetter line must be `@JsonSetter(nulls = Nulls.SKIP)` – getsadzeg May 20 '22 at 15:23

score 2 · Answer 2 · answered Feb 21 '18 at 11:56

What i did in my case is to set a default value on the getter

public class User {
    private Long id = 42L;
    private String name = "John";

    public getName(){
       //You can check other conditions
       return name == null? "John" : name;
    }
}

I guess this will be a pain for many fields but it works in the simple case of less number of fields

jeff porter · Answer 3 · 2016-04-07T13:51:22.290

-1

To skip using TypeAdapters, I'd make the POJO do a null check when the setter method is called.

Or look at

@JsonInclude(value = Include.NON_NULL)

The annotation needs to be at Class level, not method level.

@JsonInclude(Include.NON_NULL) //or Include.NON_EMPTY, if that fits your use case 
public static class RequestPojo {
    ...
}

For Deserialise you can use following at class level.

@JsonIgnoreProperties(ignoreUnknown = true)

edited Apr 07 '16 at 13:51

answered Apr 06 '16 at 13:39

jeff porter

6,560
13
65
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@JsonInclude(value = Include.NON_NULL) seems to be only working when serializing, not when deserializing. – fweigl Apr 06 '16 at 14:36

Felk · Answer 4 · 2018-04-04T23:36:44.770

Albeit not the most concise solution, with Jackson you can handle setting the properties yourself with a custom @JsonCreator:

public class User {
    Long id = 42L;
    String name = "John";

    @JsonCreator
    static User ofNullablesAsOptionals(
            @JsonProperty("id") Long id,
            @JsonProperty("name") String name) {
        User user = new User();
        if (id != null) user.id = id;
        if (name != null) user.name = name;
        return user;
    }
}

Ignore null fields when DEserializing JSON with Gson or Jackson

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