JacksonTest.java

package javatest;

import com.google.common.collect.ImmutableMap;
import org.codehaus.jackson.JsonGenerator;
import org.codehaus.jackson.JsonParser;
import org.codehaus.jackson.annotate.JsonCreator;
import org.codehaus.jackson.annotate.JsonProperty;
import org.codehaus.jackson.map.DeserializationContext;
import org.codehaus.jackson.map.JsonDeserializer;
import org.codehaus.jackson.map.JsonSerializer;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializerProvider;
import org.codehaus.jackson.map.annotate.JsonDeserialize;
import org.codehaus.jackson.map.annotate.JsonSerialize;
import org.codehaus.jackson.type.TypeReference;

import java.io.IOException;
import java.util.Collections;
import java.util.List;
import java.util.Map;

public final class JacksonTest
{
    public static class MapSerializer
            extends JsonSerializer<Map<String, String>>
    {
        @Override
        public void serialize(Map<String, String> value, JsonGenerator jgen, SerializerProvider provider)
                throws IOException
        {
            jgen.writeStartArray();
            for (Map.Entry<String, String> entry : value.entrySet()) {
                jgen.writeStartObject();
                jgen.writeObjectField("key", entry.getKey());
                jgen.writeObjectField("value", entry.getValue());
                jgen.writeEndObject();
            }
            jgen.writeEndArray();
        }
    }

    private static class MapDeserializer
            extends JsonDeserializer<Map<String, String>>
    {
        @SuppressWarnings("PublicField")
        private static class Entry
        {
            @JsonProperty public String key;
            @JsonProperty public String value;
        }

        @Override
        public Map<String, String> deserialize(JsonParser jp, DeserializationContext ctxt)
                throws IOException
        {
            List<Entry> list = jp.readValueAs(new TypeReference<List<Entry>>() {});
            ImmutableMap.Builder<String, String> map = ImmutableMap.builder();
            for (Entry entry : list) {
                map.put(entry.key, entry.value);
            }
            return map.build();
        }
    }

    public static class Model
    {
        private final Map<String, String> map;

        @JsonCreator
        public Model(@JsonProperty("map") @JsonDeserialize(using = MapDeserializer.class) Map<String, String> map)
        {
            this.map = ImmutableMap.copyOf(map);
        }

        @JsonProperty
        @JsonSerialize(using = MapSerializer.class)
        public Map<String, String> getMap()
        {
            return map;
        }
    }

    public static void main(String[] args)
            throws Exception
    {
        Model original = new Model(Collections.singletonMap("test", "test"));

        ObjectMapper mapper = new ObjectMapper();
        String json = mapper.writeValueAsString(original);
        Model deserialized = mapper.readValue(json, Model.class);

        System.out.println(json);
        System.out.println(original.getMap().equals(deserialized.getMap()));
    }
}