CODEWITHSUNDEEP
javajsonjacksondeserializationjson-deserialization
DMA
DMA

Reputation: 1043

Adding Custom deserialization class to already exsisting @JsonDeserialize annotation using jackson

I am trying to deserialize json by writing custom deserializer. Here is my code.

public class EventLoginDeserializer extends StdDeserializer<EventLogin> {

    public EventLoginDeserializer() {
        this(null);
    }

    public EventLoginDeserializer(Class<EventLogin> event) {
        super(event);
    }

    @Override
    public EventLogin deserialize(JsonParser jsonParser, DeserializationContext deserializationContext)
            throws IOException, JsonProcessingException {
        JsonNode jsonNode = jsonParser.getCodec().readTree(jsonParser);
        return EventLogin.builder().displayName(jsonNode.get("display_name"))
                .timestamp(DateTime.now()).build();
    }

    @Override
    public Class<EventLogin> handledType() {
        return EventLogin.class;
    }
}

And here is the snippet of my main class.

ObjectMapper mapper = new ObjectMapper();
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);

SimpleModule module = new SimpleModule();
module.addDeserializer(EventLogin.class, new EventLoginDeserializer());
mapper.registerModule(module);

String json = "{\"display_name\": \"Test Deserialization\", \"user_name\": \"test\"}";

EventLogin eventLogin = mapper.readValue(json, EventLogin.class);
System.out.println("readValue :::: " + eventLogin);

I have a requirement wherein I've to take an already existing @JsonDeserialize annotated model class in the jar file and add one more deserialization class above. I meant here is the same of an already existing class in a source file.

@AutoValue
@JsonDeserialize(builder = AutoValue_EventLogin.Builder.class)
@JsonInclude(JsonInclude.Include.NON_NULL)
public abstract class EventLogin
{
    public abstract String displayName();
    public abstract DateTime timestamp();

    @AutoValue.Builder
    public abstract static class Builder implements Login.Builder<Builder> {

    public abstract Builder displayName(String displayName);
        public abstract Builder emailId(DateTime timestamp);

        public abstract EventLogin build();
    }
}

The problem is that since @JsonDeserialize already exists in the jar file, so adding custom deserializer was not being considered at all. Meaning, the overridden deserialize method the custom deserializer class is not being executed.

So how to overcome this problem?

Upvotes: 4

Views: 4232

Answers (1)

DMA
DMA

Reputation: 1043

Go the solution. Jackson lets us override those attribute-specified values with mixins, so we could create a mixin class and add in the object mapper. 

@JsonDeserialize(using = EventLoginDeserializer.class)
public static class EventLoginMixIn{}

and then in our main class

ObjectMapper mapperWithMixin = new ObjectMapper()
        .addMixIn(EventLogin.class, EventLoginMixIn.class);

// Deserialize the eventlogin
EventLogin eventLogin = mapperWithMixin.readValue(actualJson, EventLogin.class);

Upvotes: 4

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