java - 方法提取、泛型、反射

Question

第一个代码:

    Bond[] bonds = null;
    try
    {
        JSONArray jsonArray = new JSONArray(result);
        bonds = new Bond[jsonArray.length()];
        for (int i = 0; i < jsonArray.length(); i++)
        {
            JSONObject json = jsonArray.getJSONObject(i);
            bonds[i] = new Bond(json);
        }
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }

第二:

    Announcement[] announcements = null;
    try
    {
        JSONArray jsonArray = new JSONArray(result);
        announcements = new Announcement[jsonArray.length()];
        for (int i = 0; i < jsonArray.length(); i++)
        {
            JSONObject json = jsonArray.getJSONObject(i);
            announcements[i] = new Announcement(json);
        }
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }

我正在考虑提取一个涵盖这两个代码的方法。我认为该方法应该或多或少像这样:

static Object[] getObjectsArray(String jsonString, Class<?> cls)
{
    Object[] objects = null;
    try
    {
        JSONArray jsonArray = new JSONArray(jsonString);
        objects = (Object[]) Array.newInstance(cls, jsonArray.length());
        for (int i = 0; i < jsonArray.length(); i++)
        {
            JSONObject json = jsonArray.getJSONObject(i);
            objects[i] = new Announcement(json); // FIXME: How to pass "json" arg to the constructor with cls.newInstance()?
        }
    }
    catch (JSONException e)
    {
        e.printStackTrace();
    }
    return objects;
}

因此，稍后我可以调用 Bond[] bond = (Bond[]) getObjectsArray(jsonArray, Bond)，而不是第一个代码。

这是最有问题的一行:

objects[i] = new Announcement(json); // FIXME: How to pass "json" arg to the constructor with cls.newInstance()?

Answer 1

您可以使用以下语法来使用带参数的构造函数(我假设构造函数的参数是 JSONObject 并且构造函数是公共(public)的 - 如果不是，请使用 getDeclaredConstructor 方法):

Class<Announcement> cls = Announcement.class; //the second argument of your method
objects[i] = cls.getConstructor(JSONObject.class).newInstance(json);