没有为此对象定义无参数构造函数 - Hangfire 调度程序

Question

我刚刚在我的 MVC 网站中安装了 Hangfire 包。 我创建了一个 Startup 类

[assembly: OwinStartup(typeof(Website.Startup))]

namespace Website
{
    public partial class Startup
    {
        public void Configuration(IAppBuilder app)
        {
            Hangfire.ConfigureHangfire(app);
            Hangfire.InitializeJobs();
        }
    }
}

还有一个 Hangfire 课程

public class Hangfire
{
    public static void ConfigureHangfire(IAppBuilder app)
    {
        app.UseHangfire(config =>
        {
            config.UseSqlServerStorage("DefaultConnection");
            config.UseServer();
            config.UseAuthorizationFilters(); 
        });
    }

    public static void InitializeJobs()
    {
        RecurringJob.AddOrUpdate<CurrencyRatesJob>(j => j.Execute(), "* * * * *");
    }
}

另外，我在单独的类库中创建了一个新作业

public class CurrencyRatesJob
{
    private readonly IBudgetsRepository budgetsRepository;

    public CurrencyRatesJob(IBudgetsRepository budgetsRepository)
    {
        this.budgetsRepository = budgetsRepository;
    }

    public void Execute()
    {
        try
        {
            var budgets = new BudgetsDTO();
            var user = new UserDTO();

            budgets.Sum = 1;
            budgets.Name = "Hangfire";
            user.Email = "email@g.com";

            budgetsRepository.InsertBudget(budgets, user);
        }
        catch (Exception ex)
        {
            var message = ex.ToString();
            throw new NotImplementedException(message);
        }
    }
}

所以当我运行应用程序时，在 Hangfire 的仪表板中我收到以下错误：

Failed An exception occurred during job activation.
System.MissingMethodException

No parameterless constructor defined for this object.

System.MissingMethodException: No parameterless constructor defined for this object.
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.RuntimeType.CreateInstanceDefaultCtor(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance(Type type, Boolean nonPublic)
   at System.Activator.CreateInstance(Type type)
   at Hangfire.JobActivator.ActivateJob(Type jobType)
   at Hangfire.Common.Job.Activate(JobActivator activator)

所以，我有点迷路了。我错过了什么？

Answer 1

您似乎没有将 Hangfire 连接到您正在使用的 IoC 容器，因此它使用其默认策略来创建请求的类型，在您的具体示例中意味着调用：

System.Activator.CreateInstance(typeof(CurrencyRatesJob));

由于CurrencyRatesJob 类没有默认的无参数构造函数，因此失败并显示您在问题中显示的错误消息。

要将 Hangfire 连接到您的 IoC 基础架构，您需要创建自己的 JobActivator 类来覆盖 ActivateJob 方法并使用配置的 IoC 容器来创建请求的作业类型的实例。

使用 Unity 作为容器的示例 (UnityJobActivator) 可以在 here 中找到，Funq 容器的示例 (FunqJobActivator) 可以在 here 中找到。

Hangfire documentation 中描述了该过程，Hangfire github repo 中提供了几种容器类型的标准实现

Answer 2

您需要注入依赖项才能使其正常工作。 安装 nuget unity 包：

Install-Package Hangfire.Unity

然后在 Global.asax 上注册，您将拥有 BootStraper 初始化方法。导航到引导程序类并在初始化中有以下代码，

DependencyResolver.SetResolver(new UnityDependencyResolver(container));

如果您使用 Unity，完整的代码将如下所示。

public static class Bootstrapper
{
    public static IUnityContainer Initialise()
    {
        var container = BuildUnityContainer();

        DependencyResolver.SetResolver(new UnityDependencyResolver(container));

        return container;
     }



 private static IUnityContainer BuildUnityContainer()
 {
    var container = new UnityContainer();       
    GlobalConfiguration.Configuration.UseUnityActivator(container);
    RegisterTypes(container);
    return container;
 }

Answer 3

我在这里找到了一个非常简单的讨论：Hangfire Discussion

我将包含我的示例代码：

public class Job : IJob
{
    private readonly IService _service;
    private readonly IDbContext _context;

    public Job()
    {
         // this needs to be here, although this won't be used in the actual running
    }

    public Job(IService service, IDbContext context) : this()
    {
        _service = service;
        _context = context;
    }

    public override void Run(SomeModel searchLocationModel)
    {
    }
}

我对 Hangfire 的实际调用如下：

IJob job = NinjectWebCommon.Kernel.TryGet<Job>();

RecurringJob.AddOrUpdate(job.ToString(), () => job.Run(model), Cron.Weekly, TimeZoneInfo.Utc);

Answer 4

以上答案都无法在我们的项目中实现。所以我们最终创建了一个后台作业助手，它使用反射来实例化类（没有无参数构造函数），然后调用该方法。

using Newtonsoft.Json.Linq;
using System;
using System.Reflection;

public static class BackgroundJobHelper
{
    public static object Execute(string userId, Type classType, string functionName, object[] param)
    {
        ServiceFactory serviceFactory = new ServiceFactory(userId);
        var classToInvoke = Activator.CreateInstance(classType, new object[] { serviceFactory });
        return Send(classType, classToInvoke, functionName, param);
    }

    private static object Send(Type classType, object className, string functionName, object[] param, Type[] fnParameterTypes = null)
    {
        MethodInfo methodInfo;
        if (!fnParameterTypes.IsNullOrEmpty())
        {
            methodInfo = classType.GetMethod(functionName, fnParameterTypes);
        }
        else
        {
            methodInfo = classType.GetMethod(functionName);
        }
        var methodParameters = methodInfo.GetParameters();
        //Object of type 'System.Int64' cannot be converted to type 'System.Int32'. While deserializing int is converted into long hence explictly make it Int32.
        for (int i = 0; i < param.Length; i++)
        {
            var methodParameterType = methodParameters[i].ParameterType;
            if (param[i] != null)
            {
                if (param[i] is long l)
                {
                    if (l >= int.MinValue && l <= int.MaxValue) param[i] = (int)l;
                }
                else if (param[i].GetType() == typeof(JObject))
                {
                    param[i] = (param[i] as JObject).ToObject(methodParameterType);
                }
                else if (param[i].GetType() == typeof(JArray))
                {
                    param[i] = (param[i] as JArray).ToObject(methodParameterType);
                }
            }
        }
        return methodInfo.Invoke(className, param);
    }
}

用法：

var backgroundJob = new BackgroundJobClient(new SqlServerStorage(db.Database.Connection));
var result = backgroundJob.Schedule(() => BackgroundJobHelper.Execute(userId, this.GetType(), nameof(this.SendMailAsync), new object[] { projectId, remarks }), TimeSpan.FromSeconds(30));