getJSONObject與optJSONObject的區別,結合源碼分析

*json解析常見問題:

• getJSONObject與optJSONObject的區別,下面結合源碼和案例來分析當我們使用這兩週方法來解析數據時,哪種比較好.

• 源碼分析:

//使用getJSONObject時,如果返回的對象不是JSONObject,拋出JSONException異常
   /**
     * Returns the value mapped by {@code name} if it exists and is a {@code
     * JSONObject}.
     * @throws JSONException if the mapping doesn't exist or is not a {@code
     *     JSONObject}.
     */

    public JSONObject getJSONObject(String name) throws JSONException {
        Object object = get(name);
        if (object instanceof JSONObject) {
            return (JSONObject) object;
        } else {
            throw JSON.typeMismatch(name, object, "JSONObject");
        }
    }



//使用optJSONObject時,當返回結果不是JSONObject時,這裏不會拋異常,而是返回null
    /**
     * Returns the value mapped by {@code name} if it exists and is a {@code
     * JSONObject}. Returns null otherwise.
     */
    public JSONObject optJSONObject(String name) {
        Object object = opt(name);
        return object instanceof JSONObject ? (JSONObject) object : null;
    }

• 結合項目代碼分析使用場景

   /**
    * 僞代碼如下
    **/
    public class GetGoodsCollectListFactory {
        private String ERROR_MSG  = "errorMsg";
        private String ERROR_CODE = "errorCode";
        private String RESULT     = "result";

        /**
         * 商品列表,解析獲取到的json數據
         *
         * @param param
         * @return
         */
        public CollectListInfo getGoodsCollectListParse(String param) {
            String BOOK_MARK_BO_LIST = "favorGoodsList";
            CollectListInfo collectList = new CollectListInfo();
            List<CollectInfo> list = new ArrayList<CollectInfo>();
            ResponseInfo responseInfo = null;
            CollectInfo info = null;
            try {
                // 請求獲取json結果
                JSONObject jsonObject = new JSONObject(HttpRequestClient.executeRequest(Constant.Url.GET_FOLLOW_GOODS_URL, param, true));
                responseInfo = new ResponseInfo();
                if (jsonObject.getBoolean(RESULT)) {
                    responseInfo.setResult(true);
                    JSONArray jsonArray = jsonObject.getJSONArray(BOOK_MARK_BO_LIST);
                    collectList.setTotalPage(jsonObject.getInt(Constant.TOTAL_PAGE_NAME));
                    for (int i = 0; i < jsonArray.length(); i++) {
                        info = collectList.getCollectInfo();
                        SONObject object = jsonArray.getJSONObject(i);
                        JSONArray activityItemList = object.optJSONArray("activityItemList");
                        ArrayList<ActivityCollectInfo> activityCollectInfos = new ArrayList<ActivityCollectInfo>();

                        //因爲object.optJSONArray("activityItemList");如果解析不到會直接返null
                        if (activityItemList != null && activityItemList.size() > 0) {
                            for (int j = 0; j < activityItemList.length(); j++) {

                                //使用optJSONObject(i)會莫名解析不了下面數據:如optString("activityId"));
                                // 當activityid爲null時,不會拋錯,但是下面的方法不走,因此換用getJSONObject(i);
                                //JSONObject activityItemobj = activityItemList.optJSONObject(i);

                                JSONObject activityItemobj = activityItemList.getJSONObject(i);
                                ActivityCollectInfo activityCollectInfo = new ActivityCollectInfo();
                                activityCollectInfo.setActivityId(activityItemobj.optString("activityId"));
                                activityCollectInfo.setActivityName(activityItemobj.optString("activityName"));
                                activityCollectInfo.setActivityType(activityItemobj.optInt("activityType"));
                                activityCollectInfo.setLargessFlag(activityItemobj.optInt("largessFlag"));
                                activityCollectInfo.setLargessMoney(activityItemobj.optInt("largessMoney"));
                                activityCollectInfo.setLargessNumber(activityItemobj.optInt("largessNumber"));
                                activityCollectInfos.add(activityCollectInfo);
                            }
 ...                       
                        }
                }

溫故而知新，可以爲師矣.