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How to write a ServiceStack plugin that requires both a request and a Dtos response

I need to serve localized data. All response Dtos that are localized have the same properties. That is, I defined an interface ( ILocalizedDto) to mark these Dtos. On the request side, there is a request ILocalizedRequestfor requests requiring localization.

Using IPlugin, I have already managed to implement the required function. However, I am sure that the implementation is not thread safe, and in addition, I do not know if I can use IHttpRequest.GetHashCode () as an identifier for one request / response cycle.

What would be the correct way to implement the ServiceStack plugin that uses both the request and the Dto response? That is, is there some kind of IHttpRequest.Context for storing data, or can I get a dto request during the response?

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();
    }
}
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1 answer

Firstly: why do you need the query itself when all you need is a property value Language?

The following code is a legitimate solution for your scenario:

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);
      }
    }
  }
}

An interesting thing here var language = request.GetParam(LanguageKey) ?? request.GetItem(LanguageKey);is that it allows you to enter the language with either an HTTP header or a cookie (if applicable) with the key "X-Language". (You can also do one more ?? DefaultLanguageto enter the default language for translation ...)

, Language Items .

: , @mythz, DTO request.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);
    }
}
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