在HangFire中添加HttpContext

Question

我是HangFire的初学者，期待着每月使用HangFire在我的web应用程序中调用一些操作。但这些操作需要HttpContext。

那么我的问题是:有没有办法在HangFire项目中添加(或创建)一个httpcontext？

我试着用谷歌搜索，但没有合适的答案。谢谢你的帮忙!

我找到了一个简短的讨论。遗憾的是，答案是“不可能”。更新: Ref https://discuss.hangfire.io/t/passing-site-url-to-hangfire-recurrent-jobs/2641

Answer 1

我有一个类似的场景，系统在很大程度上依赖于会话，我采用了同样的方法来伪造HttpContext并传递会话变量。

在我的方法中，我接收到一个可序列化的上下文，其中包含所有会话变量：

public static void MyMethod(Hangfire.Server.PerformContext context, Hangfire.IJobCancellationToken cancellationToken, 
        SerializeableHttpContext serializeableHttpContext, ... etc)
{
    using (var fakeContext = serializeableHttpContext.CreateFakeHttpContext()) {
    // ...
    }
}

在入队期间，我将当前上下文传递给我的可序列化上下文，它将捕获所有当前变量：

// null and null are injected by Hangfire
Hangfire.BackgroundJob.Enqueue(() => MyMethod(null, null, new SerializeableHttpContext(System.Web.HttpContext.Current), etc..);

这就是奇迹发生的地方。这将保存所有会话变量，并恢复它们。请注意，使用IDispose很重要，因为您的下一个Hangfire作业不想继承前一个作业的假HttpContext，因此您需要清理HttpContext。

/// <summary>
/// This serializes HttpContext with primitive Session variables
/// </summary>
[Serializable]
public class SerializeableHttpContext
{
    public Uri RequestUrl { get; set; }
    public Dictionary<string, object> SessionVariables { get; set; }

    /// <summary>
    /// Given a real HttpContext (you can pass System.Web.HttpContext.Current), this saves all useful information 
    /// into this serializable class, so that you can later reuse (restore) a cloned fake HttpContext
    /// </summary>
    /// <param name="httpContext">You'll probably want to pass System.Web.HttpContext.Current</param>
    public SerializeableHttpContext(HttpContext httpContext)
    {
        this.RequestUrl = httpContext.Request.Url;

        // Save all Session variables
        this.SessionVariables = new Dictionary<string, object>();
        foreach (object objkey in httpContext.Session.Keys)
        {
            string key = objkey as string;
            if (key == null || httpContext.Session[key] == null)
                continue;
            Type type = httpContext.Session[key].GetType();

            if (type.IsPrimitive || type == typeof(string))
            {
                try
                {
                    // ignore if not serializable
                    object val = JsonConvert.DeserializeObject(JsonConvert.SerializeObject(httpContext.Session[key]));
                    this.SessionVariables.Add(key, httpContext.Session[key]);
                }
                catch (Exception) { }
            }
        }

    }

    /// This is for internal usage, when deserializing.
    public SerializeableHttpContext()
    {
    }

    /// <summary>
    /// Deserializes into a Fake HttpContext
    /// </summary>
    /// <returns></returns>
    protected HttpContext Deserialize()
    {
        var httpRequest = new HttpRequest("", this.RequestUrl.AbsoluteUri, "");
        var stringWriter = new StringWriter();
        var httpResponse = new HttpResponse(stringWriter);
        var httpContext = new HttpContext(httpRequest, httpResponse);

        var sessionContainer = new HttpSessionStateContainer("id", new SessionStateItemCollection(),
                                                new HttpStaticObjectsCollection(), 10, true,
                                                HttpCookieMode.AutoDetect,
                                                SessionStateMode.InProc, false);

        httpContext.Items["AspSession"] = typeof(HttpSessionState).GetConstructor(
                                    BindingFlags.NonPublic | BindingFlags.Instance,
                                    null, CallingConventions.Standard,
                                    new[] { typeof(HttpSessionStateContainer) },
                                    null)
                            .Invoke(new object[] { sessionContainer });

        // Restore session variables
        if (this.SessionVariables != null)
            foreach (string key in this.SessionVariables.Keys)
                httpContext.Session[key] = this.SessionVariables[key];

        // Restore context variables
        if (this.ContextVariables != null)
            foreach (string key in this.ContextVariables.Keys)
                httpContext.Items[key] = this.ContextVariables[key];

        return httpContext;
    }

    /// <summary>
    /// Deserializes this class back into a fake HttpContext, and automatically sets that into System.Web.HttpContext.Current
    /// Don't forget to DISPOSE this instance at the end, so that the Context is cleared (else Hangfire will reuse this thread with previous HttpContext)
    /// </summary>
    public FakeHttpContext CreateFakeHttpContext()
    {
        return new FakeHttpContext(this.Deserialize());
    }

    public class FakeHttpContext : IDisposable
    {
        HttpContext previousContext;
        public FakeHttpContext(HttpContext context)
        {
            previousContext = HttpContext.Current;
            HttpContext.Current = context;
        }
        public void Dispose()
        {
            HttpContext.Current = previousContext; // previousContext is probably null, but one might be using FakeHttpContexts even inside an existing web context
        }
    }
}

Answer 2

解决这个问题3天后，我发现在HangFire中创建一个假HttpContext是可能的。在这个伪HttpContext中有很多东西需要构造。但是，您可以只初始化所需的属性，而不需要定义所有属性。

非常感谢@jbl