Azure ServiceBus from Xamarin Forms PCL

问题

How is brokered messaging via Azure Service Bus done from a Xamarin Forms PCL...is there an SDK, library or plugin? If there is a way to hand roll a brokered message, I suppose it could be accomplished with an HttpClient & the REST API ...

回答1:

I finally have a working method for posting a message to an Azure Service Bus Queue from a Xamarin PCL! The way to do this is via an HttpClient.

Gotchas that made the solution elusive:

The nuget package for Microsoft.ServiceBus.Messaging will happily install, but has no exposure to the portable class.
WebClient examples abound, but there is no webclient available in the PCL!
PCL has no native crypto for HMACSHA256 for Shared Access Signature tokens. Get the PCLCrypto package from nuget.
Some documentation says request headers of Content-Type : application/atom+xml;type=entry;charset=utf-8, and BrokerProerties are required. Ain't so!

The path to post to is: BaseServiceBusAddress + queue + "/messages"

public const string ServiceBusNamespace = [YOUR SERVICEBUS NAMESPACE];

public const string BaseServiceBusAddress = "https://" + ServiceBusNamespace + ".servicebus.windows.net/";

/// <summary>
/// The get shared access signature token.
/// </summary>
/// <param name="sasKeyName">
/// The shared access signature key name.
/// </param>
/// <param name="sasKeyValue">
/// The shared access signature key value.
/// </param>
/// <returns>
/// The <see cref="string"/>.
/// </returns>
public static string GetSasToken(string sasKeyName, string sasKeyValue)
{
    var expiry = GetExpiry();
    var stringToSign = WebUtility.UrlEncode(BaseServiceBusAddress ) + "\n" + expiry;

    var algorithm = WinRTCrypto.MacAlgorithmProvider.OpenAlgorithm(MacAlgorithm.HmacSha256);
    var hasher = algorithm.CreateHash(Encoding.UTF8.GetBytes(sasKeyValue));
    hasher.Append(Encoding.UTF8.GetBytes(stringToSign));
    var mac = hasher.GetValueAndReset();
    var signature = Convert.ToBase64String(mac);

    var sasToken = string.Format(CultureInfo.InvariantCulture, "SharedAccessSignature sr={0}&sig={1}&se={2}&skn={3}", WebUtility.UrlEncode(baseAddress), WebUtility.UrlEncode(signature), expiry, sasKeyName);
    return sasToken;
}

/// <summary>
/// Posts an order data transfer object to queue.
/// </summary>
/// <param name="orderDto">
/// The order data transfer object.
/// </param>
/// <param name="serviceBusNamespace">
/// The service bus namespace.
/// </param>
/// <param name="sasKeyName">
/// The shared access signature key name.
/// </param>
/// <param name="sasKey">
/// The shared access signature key.
/// </param>
/// <param name="queue">
/// The queue.
/// </param>
/// <returns>
/// The <see cref="Task"/>.
/// </returns>
public static async Task<HttpResponseMessage> PostOrderDtoToQueue(OrderDto orderDto, string serviceBusNamespace, string sasKeyName, string sasKey, string queue)
{
    using (var client = new HttpClient())
    {
        client.BaseAddress = new Uri(BaseServiceBusAddress);
        client.DefaultRequestHeaders.Accept.Clear();

        var token = GetSasToken(sasKeyName, sasKey);
        client.DefaultRequestHeaders.Add("Authorization", token);

        HttpContent content = new StringContent(JsonConvert.SerializeObject(orderDto), Encoding.UTF8);
        content.Headers.ContentType = new MediaTypeHeaderValue("application/json");

        var path = BaseServiceBusAddress + queue + "/messages";

        return await client.PostAsync(path, content);
    }
}

/// <summary>
///     Gets the expiry for a shared access signature token
/// </summary>
/// <returns>
///     The <see cref="string" /> expiry.
/// </returns>
private static string GetExpiry()
{
    var sinceEpoch = DateTime.UtcNow - new DateTime(1970, 1, 1);
    return Convert.ToString((int)sinceEpoch.TotalSeconds + 3600);
}

}

来源：https://stackoverflow.com/questions/39753431/azure-servicebus-from-xamarin-forms-pcl

标签

xamarin.forms

azureservicebus