Retrofit converter based on Jackson instead of Gson.

JacksonConverter

public class JacksonConverter implements Converter
{
  private final ObjectMapper mapper;

	public JacksonConverter(ObjectMapper mapper)
	{
		this.mapper = mapper;
	}

	@Override public Object fromBody(TypedInput body, Type type) throws ConversionException
	{
		String charset = "UTF-8";
		if (body.mimeType() != null)
		{
			charset = MimeUtil.parseCharset(body.mimeType());
		}

		InputStreamReader isr = null;
		try
		{
			isr = new InputStreamReader(body.in(), charset);
			return mapper.readValue(isr, TypeFactory.rawClass(type));
		}
		catch (IOException e)
		{
			throw new ConversionException(e);
		}
		finally
		{
			if (isr != null)
			{
				try
				{
					isr.close();
				}
				catch (IOException ignored)
				{
				}
			}
		}
	}

	@Override public TypedOutput toBody(Object object)
	{
		try
		{
			return new JsonTypedOutput(mapper.writeValueAsBytes(object));
		}
		catch (JsonProcessingException e)
		{
			throw new AssertionError(e);
		}
	}

	private static class JsonTypedOutput implements TypedOutput
	{
		private final byte[] jsonBytes;

		JsonTypedOutput(byte[] jsonBytes)
		{
			this.jsonBytes = jsonBytes;
		}

		@Override public String fileName()
		{
			return null;
		}

		@Override public String mimeType()
		{
			return "application/json; charset=UTF-8";
		}

		@Override public long length()
		{
			return jsonBytes.length;
		}

		@Override public void writeTo(OutputStream out) throws IOException
		{
			out.write(jsonBytes);
		}
	}
}