如何编写一个需要请求和响应Dtos的ServiceStack插件

Question

我需要服务本地化数据.本地化的所有响应Dtos共享相同的属性.即我定义了一个接口(ILocalizedDto)来标记那些Dtos.在请求方面,有一个ILocalizedRequest要求本地化的请求.

使用IPlugin我已经设法实现所需的功能.但是我很确定实现不是线程安全的,另外我不知道我是否可以使用IHttpRequest.GetHashCode()作为一个请求/响应周期的标识符.

实现一个使用请求和响应Dto的ServiceStack插件的正确方法是什么？即是否存在一些IHttpRequest.Context来存储数据或者是否可以在响应时获取请求？

internal class LocalizationFeature : IPlugin
{
    public static bool Enabled { private set; get; }

    /// <summary>
    ///     Activate the localization mechanism, so every response Dto which is a <see cref="ILocalizedDto" />
    ///     will be translated.
    /// </summary>
    /// <param name="appHost">The app host</param>
    public void Register(IAppHost appHost)
    {
        if (Enabled)
        {
            return;
        }
        Enabled = true;
        var filter = new LocalizationFilter();
        appHost.RequestFilters.Add(filter.RequestFilter);
        appHost.ResponseFilters.Add(filter.ResponseFilter);
    }
}

// My request/response filter
public class LocalizationFilter
{
    private readonly Dictionary<int,ILocalizedRequest> localizedRequests = new Dictionary<int, ILocalizedRequest>();

    public ILocalizer Localizer { get; set; }

    public void RequestFilter(IHttpRequest req, IHttpResponse res, object requestDto)
    {
        var localizedRequest = requestDto as ILocalizedRequest;
        if (localizedRequest != null)
        {
            localizedRequests.Add(GetRequestId(req), localizedRequest);
        }
    }

    public void ResponseFilter(IHttpRequest req, IHttpResponse res, object response)
    {
        var requestId = GetRequestId(req);
        if (!(response is ILocalizedDto) || !localizedRequests.ContainsKey(requestId))
        {
            return;
        }

        var localizedDto = response as ILocalizedDto;
        var localizedRequest = localizedRequests[requestId];
        localizedRequests.Remove(requestId);

        Localizer.Translate(localizedDto, localizedRequest.Language);
    }

    private static int GetRequestId(IHttpRequest req)
    {
        return req.GetHashCode();
    }
}

Answer 1

首先：当您需要的只是属性的值时，为什么需要请求本身Language？

以下代码是适合您的场景的合法解决方案：

public class LocalizationFeature : IPlugin
{
  public const string LanguageKey = "X-Language";

  public void Register(IAppHost appHost)
  {
    this.GlobalRequestFilters.Add(this.InterceptRequest);
    this.GlobalResponseFilters.Add(this.InterceptResponse);
  }

  private void InterceptRequest(IRequest request,
                                IResponse response,
                                object dto)
  {
    var localizedRequest = dto as ILocalizedRequest;
    if (localizedRequest != null)
    {
      request.SetItem(LanguageKey,
                      localizedRequest.Language);
    }
  }

  private void InterceptResponse(IRequest request,
                                 IResponse response,
                                 object dto)
  {
    var localizedDto = dto as ILocalizedDto;
    if (localizedDto != null)
    {
      var language = request.GetParam(LanguageKey) ?? request.GetItem(LanguageKey);
      if (!string.IsNullOrEmpty(language))
      {
        Localizer.Translate(localizedDto,
                            language);
      }
    }
  }
}

这里有趣的是var language = request.GetParam(LanguageKey) ?? request.GetItem(LanguageKey);，它使您有机会使用 HTTP 标头、cookie 或带有“X-Language”键的表单数据（如果适用）注入语言。（您还可以执行另一个操作?? DefaultLanguage来注入默认语言进行翻译...）

如果未以这种方式提供，则从请求Language中读取请求集并使用。Items

编辑：此外，正如@mythz 所指出的request.Dto，您还可以在方法中访问请求 DTO InterceptResponse：

private void InterceptResponse(IRequest request,
                               IResponse response,
                               object dto)
{
    var localizedRequest = request.Dto as ILocalizedRequest;
    var localizedDto = dto as ILocalizedDto;
    if (localizedRequest != null
        && localizedDto != null)
    {
      Localizer.Translate(localizedDto,
                          localizedRequest.Language);
    }
}