json与javaBean，Map集合等的互相装换

/** * 把一个map变成json字符串 * @param map * @return */public static String parseMapToJson(Map<?, ?> map) {try {Gson gson = new Gson();return gson.toJson(map);} catch (Exception e) {}return null;}/** * 把一个json字符串变成对象 * @param json * @param cls * @return */public static <T> T parseJsonToBean(String json, Class<T> cls) {Gson gson = new Gson();T t = null;try {t = gson.fromJson(json, cls);} catch (Exception e) {}return t;}/** * 把json字符串变成map * @param json * @return */public static HashMap<String, Object> parseJsonToMap(String json) {Gson gson = new Gson();Type type = new TypeToken<HashMap<String, Object>>() {}.getType();HashMap<String, Object> map = null;try {map = gson.fromJson(json, type);} catch (Exception e) {}return map;}/** * 把json字符串变成集合 * params: new TypeToken<List<yourbean>>(){}.getType(), *  * @param json * @param type  new TypeToken<List<yourbean>>(){}.getType() * @return */public static List<?> parseJsonToList(String json, Type type) {Gson gson = new Gson();List<?> list = gson.fromJson(json, type);return list;}/** *  * 获取json串中某个字段的值，注意，只能获取同一层级的value *  * @param json * @param key * @return */public static String getFieldValue(String json, String key) {if (TextUtils.isEmpty(json))return null;if (!json.contains(key))return "";JSONObject jsonObject = null;String value = null;try {jsonObject = new JSONObject(json);value = jsonObject.getString(key);} catch (JSONException e) {e.printStackTrace();}return value;}