How can I convert JSON to a HashMap using Gson?

Question

I\'m requesting data from a server which returns data in the JSON format. Casting a HashMap into JSON when making the request wasn\'t hard at all but the other way seems to

Answer 1

With google's Gson 2.7 (probably earlier versions too, but I tested with the current version 2.7) it's as simple as:

Map map = gson.fromJson(jsonString, Map.class);

Which returns a Map of type com.google.gson.internal.LinkedTreeMap and works recursively on nested objects, arrays, etc.

I ran the OP example like so (simply replaced double- with single-quotes and removed whitespace):

String jsonString = "{'header': {'alerts': [{'AlertID': '2', 'TSExpires': null, 'Target': '1', 'Text': 'woot', 'Type': '1'}, {'AlertID': '3', 'TSExpires': null, 'Target': '1', 'Text': 'woot', 'Type': '1'}], 'session': '0bc8d0835f93ac3ebbf11560b2c5be9a'}, 'result': '4be26bc400d3c'}";
Map map = gson.fromJson(jsonString, Map.class);
System.out.println(map.getClass().toString());
System.out.println(map);

And got the following output:

class com.google.gson.internal.LinkedTreeMap
{header={alerts=[{AlertID=2, TSExpires=null, Target=1, Text=woot, Type=1}, {AlertID=3, TSExpires=null, Target=1, Text=woot, Type=1}], session=0bc8d0835f93ac3ebbf11560b2c5be9a}, result=4be26bc400d3c}