前言

這篇主要是在講虛擬代理人的實作部分。

實作的主題的方向是讀取中央氣象署的氣象資訊。利用中央氣象署的 API 呼叫後，取得氣象資訊，並且在等待回應時實作虛擬代理設計。

UML & Build

uml

build

WeatherProxy

使用 weather is null 判斷是否成功取得資料，並且 weatherDataTask == null || weatherDataTask.Status != TaskStatus.Running 來防止重複取得資料。

    public string GetWeather(string area)
    {
        if (weather != null)
        {
            return weather.GetWeather(area);
        }
        else
        {
            if (weatherDataTask == null|| weatherDataTask.Status != TaskStatus.Running)
            {
                weatherDataTask = Task.Run(FetchWeatherData);
            }
            return "天氣資料更新中...\n";
        }
    }

完整程式碼

public class WeatherProxy : IWeather
{
    /// <summary>
    /// https://opendata.cwa.gov.tw
    /// https://opendata.cwa.gov.tw/dist/opendata-swagger.html
    /// </summary>
    private const string Url = "https://opendata.cwa.gov.tw/api/v1/rest/datastore/F-D0047-073";
    private const string AuthorizationKey = "AuthorizationKey";
    private const string Format = "JSON";

    private IWeather weather;
    private Task weatherDataTask;

    public string GetWeather(string area)
    {
        if (weather != null)
        {
            return weather.GetWeather(area);
        }
        else
        {
            if (weatherDataTask == null|| weatherDataTask.Status != TaskStatus.Running)
            {
                weatherDataTask = Task.Run(FetchWeatherData);
            }
            return "天氣資料更新中...\n";
        }
    }

    private async Task FetchWeatherData()
    {
        weather = new Weather(await SendRequest());
    }

    private async Task<Root> SendRequest()
    {
        using var client = new HttpClient();
        var query = HttpUtility.ParseQueryString(string.Empty);
        query["Authorization"] = AuthorizationKey;
        query["format"] = Format;
        var builder = new UriBuilder(Url);
        builder.Query = query.ToString();
        string requestUri = builder.ToString();
        string responseJson = await client.GetStringAsync(requestUri);
        return string.IsNullOrEmpty(responseJson) ? null : JsonSerializer.Deserialize<Root>(responseJson);
    }
}

GitHub