How to deserialize some JSON parameters as one new variable in DTO

Question

How to deserialize JSON (using Jackson) into Java object if some JSON parameters should be used to create variable of Java DTO(but not be deserialized as dto variables).

For example I have JSON {"sideA" : 2, "sideB" : 4, "useless_parameter" : "useless_information"} and I need to get result of toString (of deserialized Java object) something like : RectangleDto{area = 8, useless_parameter = "useless_information"}

If I need to deserialize "useless_parameter" then I can use @JsonGetter("useless_information"), so what should I do with "sideA" and "sideB" if I need to take area as variable of RectangleDto? I already have a method for conversion JSON parameters into this variable.

I think this is what you are looking for https://stackoverflow.com/questions/14362247/jackson-adding-extra-fields-to-an-object-in-serialization — JPRLCol, Jan 31 '18 at 11:48

score 0 · Answer 1 · answered Jan 31 '18 at 11:50

0

You could add @JsonProperty for the area and also use @JsonIgnore for sideA and SideB. Please check Jackson :: adding extra fields to an object in serialization

answered Jan 31 '18 at 11:50

JPRLCol

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I thought it can be used only for serialization, but not for deserialization, when i need to use the combination of 2 JSON parameters in some method. – Yevhenii S. Jan 31 '18 at 12:01

score 0 · Accepted Answer · answered Jan 31 '18 at 12:40

Probably you need a custom deserializer:

class MyDeserializer extends StdDeserializer<RectangleDto> {

    public MyDeserializer() {
        this(null);
    }

    protected MyDeserializer(Class<?> vc) {
        super(vc);
    }

    @Override
    public RectangleDto deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
        JsonNode node = jp.getCodec().readTree(jp);
        int a = node.get("sideA").intValue();
        int b = node.get("sideB").intValue();
        String useless_parameter = node.get("useless_parameter").asText();

        RectangleDto test = new RectangleDto();
        test.setArea(a * b);
        test.setUseless_parameter(useless_parameter);

        return test;
    }
}

Then register the deserializer on the class

@JsonDeserialize(using = MyDeserializer.class)
public class RectangleDto {

    private int area;
    private String useless_parameter;
    // getters, setters...
}

Then this will work as you want:

RectangleDto r = mapper.readValue("{\"sideA\" : 2, \"sideB\" : 4, \"useless_parameter\" : \"useless_information\"}", RectangleDto.class);
System.out.println(r);

results in

RectangleDto{area=8, useless_parameter='useless_information'}

Thanks, that's actually what I wanted – Yevhenii S. Jan 31 '18 at 12:43 — Yevhenii S., Jan 31 '18 at 12:43

How to deserialize some JSON parameters as one new variable in DTO

2 Answers2