extra data while parsing boolean value in json by using Jackson

Question

When I'm parsing boolean value in JSON by using Jackson, I not only get my expected data, but also an extra key-value data. I want to deserialize the JSON into Java Beans and then serialize it into a String again after processing it. The extra data is in the finally result.Here is my JSON data:

{"is_charging": true}

But I get this after I parse it and then serialize it:

{"is_charging": true, "charging": true}

And here is my Java bean:

import com.fasterxml.jackson.annotation.JsonProperty;
import lombok.Getter;
import lombok.Setter;

@Getter
@Setter
public class Data {
    @JsonProperty("is_charging")
    public boolean isCharging; 
}

However, if I don't use the @JsonProperty , it can not deserialize the "is_charging" and deserialize it as false by default.

How can I solve this? Thanks!

Answer 1

It is the lombok.Getter and lombok.Setter annotations that cause the issue.

public class Data {
    @JsonProperty("is_charging")
    public boolean isCharging; 
}

objectMapper.writeValueAsString(new Data());

Works as expected.

The problem occurs when the @Getter and @Setter annotations are added.

I don't have experience with this lombok library but as far as I understand it creates getter and setter methods for you.

By configuring objectMapper you can disable auto detecting of getter and setter methods so only fields can be serialized and deserialized.

@Getter
@Setter
public class Data {

    @JsonProperty("is_charging;")
    public boolean isCharging;

}

public static void main(String... args) throws JsonProcessingException, IOException {

    ObjectMapper objectMapper = new ObjectMapper();

    objectMapper.configure(MapperFeature.AUTO_DETECT_GETTERS, false);
    objectMapper.configure(MapperFeature.AUTO_DETECT_IS_GETTERS, false);
    objectMapper.configure(MapperFeature.AUTO_DETECT_SETTERS, false);

    Data data = objectMapper.readValue("{\"is_charging\": true}", Data.class);

    System.out.print(objectMapper.writeValueAsString(data));
}

Outputs:

{"is_charging":true}

Note that only objectMapper.configure(MapperFeature.AUTO_DETECT_IS_GETTERS, false); is required in your case. Others are provided for reference in case you need them.

Answer 2

It is possible by changing the attribute name from isCharging to charging

@Getter
@Setter
public class Data {
    @JsonProperty("is_charging")
    public boolean charging; 
}

Result:

{"is_charging": true}

Answer 3

AUTO_DETECT_IS_GETTERS is a mapper feature that determines whether "is getter" methods are automatically detected based on standard Bean naming convention or not. If yes, then all public zero-argument methods that start with prefix "is", and whose return type is boolean are considered as "is getters". If disabled, only methods explicitly annotated are considered getters.

By default the feature is enabled. You can disable it while configuring your object mapper. Use,

disable(MapperFeature.AUTO_DETECT_IS_GETTERS);

which is method in ObjectMapper class