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Gson to HashMap

Posted by: admin December 20, 2017 Leave a comment

Questions:

Is there a way to convert a String containing json to a HashMap, where every key is a json-key and the value is the value of the json-key? The json has no nested values. I am using the Gson lib.

For example, given JSON:

{
"id":3,
"location":"NewYork"
}

resulting HashMap:

<"id", "3">
<"location", "NewYork">

Thanks

Answers:

Use TypeToken, as per the GSON FAQ:

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

No casting. No unnecessary object creation.

Questions:
Answers:

If I use the TypeToken solution with a Map<Enum, Object> I get “duplicate key: null”.

The best solution for me is:

String json = "{\"id\":3,\"location\":\"NewYork\"}";
Gson gson = new Gson();
Map<String, Object> map = new HashMap<String, Object>();
map = (Map<String, Object>)gson.fromJson(json, map.getClass());

Result:

{id=3.0, location=NewYork}

Questions:
Answers:

I like:

private static class MyMap extends HashMap<String,String> {};
...
MyMap map = gson.fromJson(json, MyMap.class);