FluentScheduler dependency injection in constructor

Question

I am experimenting with FluentScheduler for some background tasks in ASP.net Core API.

The job should send push notifications every day at a particular time interval based on few criteria. I had gone through the document and implemented a test functionality to print some output in the console window. It worked as expected with predicted time interval.

But the actual job I am going to do with that involves database context which provides necessary information to perform the criteria to send out the notifications.

My problem is I am unable to use constructor with parameter in MyJob class which is throwing missing method exception

PS: As per this article from Scott Hanselman, FluentScheduler seems to be quite famous but I could not get any help from online communities. But obviously, it's quite easy to grasp.

public class MyJob : IJob
{
    private ApplicationDbContext _context;

    public MyJob(ApplicationDbContext context)
    {
        _context = context;
    }

    public void Execute()
    {
        Console.WriteLine("Executed");
        SendNotificationAsync();
    }

    private async Task SendNotificationAsync()
    {
        var overdues = _context.Borrow.Join(
            _context.ApplicationUser,
            b => b.ApplicationUserId,
            a => a.Id,
            (a, b) => new { a, b })
            .Where(z => (z.a.ReturnedDate == null) && (z.a.BorrowApproval == 1))
            .Where(z => z.a.ReturnDate.Date == new DateTime().Date.AddDays(1).Date)
            .Select(z => new { z.a.ApplicationUserId, z.a.Book.ShortTitle, z.a.BorrowedDate, z.b.Token })
            .ToList();

        Console.WriteLine("Acknowledged");

        foreach (var r in overdues)
        {
            string message = "You are running late! The book '" + r.ShortTitle + "' borrowed on '" + r.BorrowedDate + "' due tomorrow.";
            Console.WriteLine(message);
            await new PushNotificationService().sendAsync(r.Token, "Due Tomorrow!", message);
        }
    }
}

Answer 1

From the source code for IJob, it looks like your class that implements IJob needs to have a parameterless default constructor. Since FluentScheduler also supports lambdas, it may be easier to have your dependency injection library create your object, then call the Execute method like so:

var myJob = new MyJob(new ApplicationDbContext());
Schedule(() => myJob.Execute()).ToRunEvery(1).Days().At(21, 15);

Or call the constructor yourself:

// Schedule a job using a factory method and pass parameters to the constructor.
Schedule(() => new MyJob(new ApplicationDbContext())).ToRunNow().AndEvery(2).Seconds();

Answer 2

Note - In the documentation it says not to use IJobFactory because it is going to be deprecated soon, but it is working for me in Production for past 3,4 months - https://github.com/fluentscheduler/FluentScheduler/issues/71

I am using Autofac and Fluent Scheduler in a Windows Console Application which uses TopShelf to run it as a Windows Service.

To use Dependency Injection in FluentScheduler you have to setup a Job Factory to resolve the dependencies.

So first setup a JobFactory by implementing IJobFactory

Like this -

public class MyJobFactory : IJobFactory
{
    public IJob GetJobInstance<T>() where T : IJob
    {
        return MyContainer.GetJobInstance<T>();
    }
}

Now in the Job Factory because I'm using Autofac I am setting up a Container which has 2 methods

1 - ConfigureDependencies() - Which is only called once to setup the Container:

2 - GetJobInstance() - Which is called by the MyJobFactory to resolve t a Job instance

public class MyContainer
{
    public static IContainer Container { get; set; }

    public static void ConfigureDependencies()
    {
        var builder = new ContainerBuilder();

        // Jobs
        builder.RegisterType<MyJob>().As<MyJob>();

        // DB Contexts

        // Others

        Container = builder.Build();
    }


    public static IJob GetJobInstance<T>() where T : IJob
    {
        return Container.Resolve<T>();
    }
}

Then when you Start you application/service, it will look something like this.

public void Start()
{
    // Configure Dependency Injection
    MyContainer.ConfigureDependencies();

    // Setup the Fluent Scheduler - 
    JobManager.JobFactory = new MyJobFactory();

    JobManager.UseUtcTime();

    JobManager.Initialize(new MyJobRegistry());     
}

Then I've created a Job by adding 2 constructors -

1 - Parameter-less

2 - The constructor with Injected Objects

e.g.

public class MyJob : IJob
{
    public static string JobName = "MyJob";

    private readonly ICompaniesProvider _companiesProvider;

    // parameter-less constructor
    public MyJob() { }

    // injecting HERE
    public MyJob(ICompaniesProvider companiesProvider)
    {
        _companiesProvider = companiesProvider;

    }

    public void Execute()
    {



    }
}

EDIT

Because of deprecated issue of IJobFactory, you could just call the Container Directly and get a Job Instance before adding it to the JobManager

public void Start()
{
    // Configure Dependency Injection
    MyContainer.ConfigureDependencies();

    JobManager.UseUtcTime();
    JobManager.Start();

    var myJob = MyContainer.GetJobInstance<MyJob>();

    Action<Schedule> schedule = s => s.ToRunEvery(1).Hours().At(0);

    JobManager.AddJob(myJob, schedule);
}

Answer 3

I have posted the similar answer here- https://stackoverflow.com/a/51167073/7166609

I have used the Application service scope, injected in the registry's constructor and used this scope to get the objects in the execute method of my job class.