JSONObject obj = new JSONObject();

obj.put("id",lab.getLabId());
obj.put("name",lab.getLabName());
obj.put("type",lab.getLabType());
obj.put("desc",lab.getLabDesc());

JSONArray array = new JSONArray();
array.put(obj);

JSONObject ob = new JSONObject();
ob.put("lab",array);

输出：{"lab":[{"id":10,"desc":"for computer science","name":"LAB-CMP-1","type":1}]}