flatten json to a list of map

优步面经

题目就是flatten json to a list of map, 有一段json，比如说如下：
{
"uuid": "abc",
"properties": {
"sessionName": "Test session name"
"waypoints": [
{"uuid": "def", "properties": {"latitude": 3}}
]
}
}
把它转化成List<Map>， map里面uuid是key, properties是value。 所以结果应该像下面

[

{“uuid”: “abc”, “properties”: {“sessionName”: “Test session name”, “waypoints”: [“def”]}},

{“uuid”: “def”, “properties”: {“latitude”: 3}},

…

]

其实就是recursion求，每次把一个object放进map以后，要用一个recursive的function 处理一下每个attribute。如果是array的话要recursive的把array里的所有object都放进res里面，并且对每个object再进行recursion

    public List<Map<String, Object>> flatternJSON(String jsonString) {

        JSONParser parser = new JSONParser();

        List<Map<String, Object>> res = new ArrayList<Map<String, Object>>();

        try {

            JSONObject jObj = (JSONObject)parser.parse(jsonString);

            Map<String, Object> map = new HashMap<String, Object>();

            String key = (String) jObj.get("uuid");

            Object value = jObj;

            map.put(key, jObj);

            recursiveProcess(jObj, res);

            return res;

        } catch (ParseException e) {

            // TODO Auto-generated catch block

            e.printStackTrace();

        }

        return null;

    }

     

    private void recursiveProcess(JSONObject jObj, List<Map<String, Object>>res) {

        Iterator iter = jObj.keySet().iterator();

        while(iter.hasNext()) {

             

            String key = (String) iter.next();

            Object obj = jObj.get(key);

            if (obj instanceof String) {

                continue;

            } else if (obj instanceof JSONArray) {

                JSONArray array = (JSONArray)obj;

                Iterator arrIter = array.iterator();

                JSONArray newArray = new JSONArray();

                while(arrIter.hasNext()) {

                    JSONObject o = (JSONObject) arrIter.next();

                    newArray.add(o.get("uuid"));

                    Map<String, Object> map = new HashMap<String, Object>();

                    map.put((String) o.get("uuid"), obj);

                    res.add(map);

                    recursiveProcess(o, res);

                }

                jObj.put(key, newArray);

                 

            } else {

                recursiveProcess((JSONObject)obj, res);

            }

        }

    }

}

http://www.1point3acres.com/bbs/thread-136248-1-1.html