android: gson performance

Question

I am trying to use gson to do my object mapping on the android emulator.

It has been ridiculously slow when processing json data around 208 kb. I do not have any hierarchies in my json.

After the object mapping is done, i can see it that gson created around 500 records.

It is taking it over 3 minutes on the android emulator to map the input json.

I have annotated my entity which comprises of strings and couple of floats.

An I missing something?

Any ideas, best practices would greatly help.

Are there any ways of quickly object mapping the json data?

        URL myURL = new URL(url);
        /* Open a connection to that URL. */
        URLConnection ucon = myURL.openConnection();
        /*
         * Define InputStreams to read from the URLConnection.
         */
        InputStream is = ucon.getInputStream();
        InputStreamReader reader = new InputStreamReader(is);
        long tickCount = System.currentTimeMillis();
        Policy[] policies = new Gson().fromJson(reader, Policy[].class);
        long endCount = System.currentTimeMillis() - tickCount;
        Log.d("Time to pull policies in milliseconds", "" + endCount);

Answer 1

I've seen questions like this come up before, and the general consensus is that Jackson is much faster than Gson. See the following links for more information:

• Jackson Vs. Gson
• Replace standard Android JSON parser for better performance?
• http://www.cowtowncoder.com/blog/archives/2009/12/entry_345.html
• https://stackoverflow.com/questions/338586/a-better-java-json-library

Here is one which specifically discusses Android: http://ubikapps.net/?p=525

Answer 2

Have you tried the mixing the GSON streaming parser with the Gson object? http://sites.google.com/site/gson/streaming (look for the Mixed read example).

This approach may help since Gson reads in an entire parse tree and then acts on it. With a large array list, reading in all elements and attempting to parse may cause lot of memory swaps (or thrashing). This approach will read in one element at a time.

Hope this helps.