Android getJSONObject与optJSONObject的区别结合源码分析

android getjsonobject与optjsonobject的区别结合源码分析

json解析常见问题:

getjsonobject与optjsonobject的区别,下面结合源码和案例来分析当我们使用这两周方法来解析数据时,哪种比较好.

源码分析:

//使用getjsonobject时,如果返回的对象不是jsonobject,抛出jsonexception异常
  /**
   * 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时,当返回结果不是jsonobject时,这里不会抛异常,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;
  }

结合项目代码分析使用场景

 /**
  * 伪代码如下
  **/
  public class getgoodscollectlistfactory {
    private string error_msg = "errormsg";
    private string error_code = "errorcode";
    private string result   = "result";

    /**
     * 商品列表,解析获取到的json数据
     *
     * @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 {
        // 请求获取json结果
        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>();

            //因为object.optjsonarray("activityitemlist");如果解析不到会直接返null
            if (activityitemlist != null && activityitemlist.size() > 0) {
              for (int j = 0; j < activityitemlist.length(); j++) {

                //使用optjsonobject(i)会莫名解析不了下面数据:如optstring("activityid"));
                // 当activityid为null时,不会抛错,但是下面的方法不走,因此换用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);
              }
 ...            
            }
        }

温故而知新，可以为师矣.