Parsing Json Feeds with google Gson

Question

I would like to know how to parse a JSON feed by items (eg. url / title / description for each item). I have had a look to the doc / api but, it didn't help me.

This is what I got so far

import com.google.gson.Gson;
import com.google.gson.JsonObject;

public class ImportSources extends Job {
    public void doJob() throws IOException {
        String json = stringOfUrl("http://feed.test/all.json");
        JsonObject jobj = new Gson().fromJson(json, JsonObject.class);
        Logger.info(jobj.get("responseData").toString());
    }
    public static String stringOfUrl(String addr) throws IOException {
        ByteArrayOutputStream output = new ByteArrayOutputStream();
        URL url = new URL(addr);
        IOUtils.copy(url.openStream(), output);
        return output.toString();
    }
}

score 9 · Accepted Answer · edited May 23 '17 at 10:29

Depends on the actual JSON format. You can in fact just create a custom Javabean class which matches the JSON format. Any fields in JSON can be mapped as String, Integer, Boolean, etc Javabean properties. Any arrays can be mapped as List properties. Any objects can be mapped as another nested Javabean property. It greatly eases further processing in Java.

Without a JSON string example from your side, it's only guessing how it would look like, so I can't give a basic example here. But I've posted similar answers before here, you may find it useful:

Gson has also an User Guide, you may find it useful as well.

Thanks for your answer, I have tried to apply the examples to the following feed: http://www.stocktwits.com/streams/all.json . I didn't manage to get any other values than null. Do I need to create two groups : stream and tweets? — Roch, Jan 11 '10 at 11:10

score 3 · Answer 2 · answered Apr 03 '10 at 05:28

3

Gson 1.4 has a new API JsonStreamParser that lets you parse multiple JSON objects one by one from a stream.

answered Apr 03 '10 at 05:28

inder

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blue01 · Answer 3 · 2013-02-11T18:59:10.407

1

You can create corresponding java classes for the json objects. The integer, string values can be mapped as is. Json can be parsed like this-

 Gson gson = new GsonBuilder().create();
 Response r = gson.fromJson(jsonString, Response.class);

Here is an example- http://rowsandcolumns.blogspot.com/2013/02/url-encode-http-get-solr-request-and.html

edited Feb 11 '13 at 18:59

answered Feb 11 '13 at 18:51

blue01

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score 0 · Answer 4 · answered Jan 10 '10 at 23:20

0

I don't know if GSON can do streaming/incremental binding (I thought it did not).

But is there specific reason to only consider that particular library? Other Java JSON processing libraries do allow such processing (you can check links the other answer has for some ideas), since it is quite important feature when processing large feeds.

answered Jan 10 '10 at 23:20

StaxMan

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Well I was using ROME for RSS feeds, and the framework I'm using contains gson, Thats why I'm trying to use it, but I'm open to any other library. – Roch Jan 11 '10 at 11:04
Ok. Like I said, I think GSON only does full document binding, but I am not 100%. For an alternative, Jackson (http://jackson.codehaus.org) does allow incremental binding, as well as multiple other operating modes. The way that works is that you need to get a JsonParser for the main thing, iterate over main JSON array or object, and call parser.readValueAs() for actual binding. User mailing list can help with details, if documentation does not have enough pointers. – StaxMan Jan 12 '10 at 05:25

Parsing Json Feeds with google Gson

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