How to parse JSON object into `Map>`

Question

I'd like to parse this JSON object:

"{
  \"Rao\":[\"Q7293658\",\"\",\"Q7293657\",\"Q12953055\",\"Q3531237\",\"Q4178159\",\"Q1138810\",\"Q579515\",\"Q3365064\",\"Q7293664\",\"Q1133815\"],
  \"Hani Durzy\":[\"\"],
  \"Louise\":[\"\",\"Q1660645\",\"Q130413\",\"Q3215140\",\"Q152779\",\"Q233203\",\"Q7871343\",\"Q232402\",\"Q82547\",\"Q286488\",\"Q156723\",\"Q3263649\",\"Q456386\",\"Q233192\",\"Q14714149\",\"Q12125864\",\"Q57669\",\"Q168667\",\"Q141410\",\"Q166028\"],
  \"Reyna\":[\"Q7573462\",\"Q2892895\",\"Q363257\",\"Q151944\",\"Q3740321\",\"Q2857439\",\"Q1453358\",\"Q7319529\",\"Q733716\",\"Q16151941\",\"Q7159448\",\"Q5484172\",\"Q6074271\",\"Q1753185\",\"Q7319532\",\"Q5171205\",\"Q3183869\",\"Q1818527\",\"Q251862\",\"Q3840414\",\"Q5271282\",\"Q5606181\"]
}"

and with that data generate a Map<String, HashSet<String>>.

Essentially I want to reverse this procedure.

All the code for this project can be found on my github page here, it's quite short.

update

        File f = new File("/home/matthias/Workbench/SUTD/nytimes_corpus/wdtk-parent/wdtk-examples/JSON_Output/user.json");

        String jsonTxt = null;

        if (f.exists())
        {
            InputStream is = new FileInputStream("/home/matthias/Workbench/SUTD/nytimes_corpus/wdtk-parent/wdtk-examples/JSON_Output/user.json");
            jsonTxt = IOUtils.toString(is);


        }
        //System.out.println(jsonTxt);


        Gson gson=new Gson(); 


        Map<String, HashSet<String>> map = new HashMap<String, HashSet<String>>();
        map=(Map<String, HashSet<String>>) gson.fromJson(jsonTxt, map.getClass());

        //// \\ // ! PRINT IT ! // \\ // \\ // \\ // \\ // \\ // \\
       for (Map.Entry<String, HashSet<String>> entry : map.entrySet()) 
       {
           System.out.println(entry.getKey()+" : " + Arrays.deepToString(map.entrySet().toArray()) );
       }

ComputerFellow · Accepted Answer · 2015-04-28T04:44:26.057

6

Using Gson

Gson gson = new Gson(); 
String json = "<YOUR_JSON_STRING_HERE>";
Map<String, HashSet<String>> map = new HashMap<String, HashSet<String>>();
map = (Map<String, HashSet<String>>) gson.fromJson(json, map.getClass());

Update:

Use TypeToken

Type type = new TypeToken<Map<String, HashSet<String>>>(){}.getType();
map = (Map<String, HashSet<String>>) gson.fromJson(json, type);

Or you could parse it...

Create an object of JSONObject
Create an object of HashMap
Iterate over jsonObj.keys() and for every key get value like jsonObj.getString(key).
Put it in the map like map.put(key, value).

edited Apr 28 '15 at 04:44

answered Apr 28 '15 at 04:17

ComputerFellow

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what is a json string? can I just read in the file with bufferedreader and that will make a json string? I've never done this before please forgive me – smatthewenglish Apr 28 '15 at 04:18
@S.Matthew_English Yes. – ComputerFellow Apr 28 '15 at 04:19
i tried to do as you said but i got a strange error, i posted what i did to to original question – smatthewenglish Apr 28 '15 at 04:34
`Expected BEGIN_OBJECT but was STRING at line 1 column 2` – smatthewenglish Apr 28 '15 at 04:35
maybe something like [this](http://stackoverflow.com/questions/9598707/gson-throwing-expected-begin-object-but-was-begin-array)? – smatthewenglish Apr 28 '15 at 04:41
Well yes, I guess this calls for a separate discussion in another thread. All the best though :-) – ComputerFellow Apr 28 '15 at 04:42
what is `Type` my IDE offers me about 20 things to import for that but I can't tell which is the one? is it something about `gson`? – smatthewenglish Apr 28 '15 at 04:46
@S.Matthew_English Yes it's from gson http://google-gson.googlecode.com/svn/tags/1.1/docs/javadocs/com/google/gson/reflect/TypeToken.html – ComputerFellow Apr 28 '15 at 04:47
maybe it's becasue the json object has `"` around it? – smatthewenglish Apr 28 '15 at 04:56

How to parse JSON object into `Map>`

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