jackson deserializer unwrapping a data field

JacksonDeserializerTest.java

import com.fasterxml.jackson.core.JsonParseException;
import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.core.JsonToken;
import com.fasterxml.jackson.databind.BeanDescription;
import com.fasterxml.jackson.databind.DeserializationConfig;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.DeserializationFeature;
import com.fasterxml.jackson.databind.JsonDeserializer;
import com.fasterxml.jackson.databind.JsonMappingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.deser.BeanDeserializerModifier;
import com.fasterxml.jackson.databind.deser.ResolvableDeserializer;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;
import com.fasterxml.jackson.databind.module.SimpleModule;
import org.junit.Test;

import java.io.IOException;

import static org.assertj.core.api.Assertions.assertThat;

public class JacksonDeserializerTest {

    @Test
    public void should_deserialize_data() throws Exception {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
        SimpleModule simpleModule = new SimpleModule();
        simpleModule.setDeserializerModifier(new BeanDeserializerModifier() {
            @Override public JsonDeserializer<?> modifyDeserializer(DeserializationConfig config, BeanDescription beanDesc, JsonDeserializer<?> deserializer)
            {
                if (beanDesc.getBeanClass() == MyEntity.class)
                    return new MyDeserializer((JsonDeserializer<MyEntity>) deserializer);
                return deserializer;
            }
        });
        mapper.registerModule(simpleModule);

        MyEntity myEntity = mapper.readValue(
                "{\"name\": \"test\", \"data\": { \"myfield\": \"test2\" } }", MyEntity.class);

        assertThat(myEntity.getName()).isEqualTo("test");
        assertThat(myEntity.getMyfield()).isEqualTo("test2");
    }

    public static class MyDeserializer extends StdDeserializer<MyEntity> implements ResolvableDeserializer {
        private final JsonDeserializer<MyEntity> defaultDeserializer;

        public MyDeserializer(JsonDeserializer<MyEntity> defaultDeserializer) {
            super(MyEntity.class);
            this.defaultDeserializer = defaultDeserializer;
        }

        @Override
        public MyEntity deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException, JsonProcessingException {
            JsonToken token = jp.getCurrentToken();
            if (token == JsonToken.START_OBJECT) {
                jp.nextToken();

                MyEntity e = new MyEntity();

                if (!"name".equals(jp.getCurrentName())) {
                    throw new JsonParseException("expected name", jp.getCurrentLocation());
                }
                e.setName(jp.nextTextValue());

                jp.nextToken();

                if (!"data".equals(jp.getCurrentName())) {
                    throw new JsonParseException("expected data", jp.getCurrentLocation());
                }
                jp.nextToken();

                defaultDeserializer.deserialize(jp, ctxt, e);

                jp.nextToken();

                return e;
            }
            
            return null;
        }

        @Override public void resolve(DeserializationContext ctxt) throws JsonMappingException
        {
            ((ResolvableDeserializer) defaultDeserializer).resolve(ctxt);
        }
    }

    public static class MyEntity {
        private String name;
        private String myfield;

        public String getName() {
            return name;
        }

        public void setName(String name) {
            this.name = name;
        }

        public String getMyfield() {
            return myfield;
        }

        public void setMyfield(String myfield) {
            this.myfield = myfield;
        }
    }
}