如何使用json将包含多个对象的json文件转换为java对象列表

Question

我正在开发一个 Java 项目，该项目获取 Twitch 上当天最流行的剪辑的 URL。为此，我使用以下代码向 twitch API 发送请求：

    private List<TwitchClip> getVideoList() {

    try {

        LocalTime midnight = LocalTime.MIDNIGHT;

        LocalDate today = LocalDate.now(ZoneId.of("Europe/Berlin"));

        LocalDateTime todayMidnight = LocalDateTime.of(today, midnight);

        String formattedStartTime;

        String formattedEndTime;

        if(String.valueOf(todayMidnight.getMonthValue()).length() != 2) {

            formattedStartTime = todayMidnight.getYear() + "-" + 0 + todayMidnight.getMonthValue() + "-" + (todayMidnight.getDayOfMonth() - 1) + "T00:00:00Z";

            formattedEndTime = todayMidnight.getYear() + "-" + 0 + todayMidnight.getMonthValue() + "-" + todayMidnight.getDayOfMonth() + "T00:00:00Z";

        }else {

            formattedStartTime = todayMidnight.getYear() + "-" + todayMidnight.getMonthValue() + "-" + (todayMidnight.getDayOfMonth() - 1) + "T00:00:00Z";

            formattedEndTime = todayMidnight.getYear() + "-" + todayMidnight.getMonthValue() + "-" + todayMidnight.getDayOfMonth() + "T00:00:00Z";

        }

        URL url = new URL("https://api.twitch.tv/helix/clips?game_id=" + Game.FORTNITE.getId() + "&first=25&started_at=" + formattedStartTime + "&ended_at=" + formattedEndTime);

        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        connection.setRequestMethod("GET");

        connection.addRequestProperty("Client-ID", "");

        File out = File.createTempFile(UUID.randomUUID().toString(), ".json");

        System.out.println("Downloaded clips data at " + out.getPath());

        writeFile(out, connection.getInputStream());

        Gson gson = new Gson();

        return gson.fromJson(new FileReader(out), new TypeToken<List<TwitchClip>>() {

        }.getType());

    } catch (IOException e) {

        e.printStackTrace();

        return null;

    }

}

Answer 1

从带有 的 json 中可以看出{ data: [{...}, {...}, {...}], pagination: {...}&nbsp; }，您得到了一个对象。您试图读取一个数组，但不是给定的对象。这个对象有一个数组data和一个对象pagination。假设您的对象TwitchData仅包含数据数组中的属性，您可以使用以下解决方案。class Result {&nbsp; &nbsp; TwitchData[] data;&nbsp; &nbsp; Pagination pagination;}class Pagination{&nbsp; &nbsp; String cursor;}创建这两个类后，您现在可以读取 json。Result r = gson.fromJson(new FileReader(out), Result.class);return r.data;这将返回数据数组，如果您愿意，也可以将其转换为列表。