xEventService

it is a Part of xDashboard on SaherElm IT Center which provides: EventBus core and RabbitMQ implementation of if

Implementing

for using the event bus, you had to create a classlib module and add a reference to this module inside it; then start to create your events. and for handling these events you had to add reference to this classlib in where you want to react to events, then create a class for handling this event which extends IXEventHandler<> interface. and finally subscribing to event handlers you want.

RabbitMQ

for using RabbitMQ Eventbus you had to:

• create it's configuration section in your appSettings.json file, like this:

  {
    ...
    "EventServiceConfiguration": {
    "Server": "YourRabbitMQHost",
    "Port": rabbitMqPort,
    "Username": "USERNAME",
    "Password": "PASSWORD",
    "AllowDynamicQueues": true
    },
    ...
  }
  

Note: in configuration if you set AllowDynamicQueues=false, you had to provide all queue named and their configs manually.

• register RabbitMQ implementation of IXEventBus in your Startup, like this:

...
public void ConfigureServices (IServiceCollection services) {
    ...
    //
    // Register RabbitMQ Event Service ...
    services.AddXEventService (Configuration);
    ...
}
...

Events

for each Event you need to implement 3 classes:

• a DTO class for provide required properties for creating Event Object instance; all properties in this class is public.

  this used when you want to get som information from another sources, such as [FromBody] in Controller Actions.

• one class which carry required data for Event object; this class must extends from XEvent class and must contains all Dto class properties in { get; protected set; } style;

• one or more class which provide Event arrounds the Event object whith propper constructor to Create it's instance;

for better undrestanding please follow this structure:

public class XPersonEventDto {
    public string Firstname { get; set; }
    public string Lastname { get; set; }
}

public class XPersonEvent : XEvent {
    public string Firstname { get; protected set; }
    public string Lastname { get; protected set; }
}

public class XCreatePersonEvent : XPersonEvent {
    public XCreatePersonEvent (
        string firstname,
        string lastname
    ) {
        Firstname = firstname;
        Lastname = lastname;
    }
}

public class XPersonCreatedEvent : XPersonEvent {
    public Guid Id { get; protected set; }

    public XPersonCreatedEvent (
        Guid id,
        string firstname,
        string lastname
    ) {
        Id = id;
        Firstname = firstname;
        Lastname = lastname;
    }
}

EventHandlers

in where you want to handle this events and react to them, for each event you had to create an event handler class.

public class XCreatePersonEventHandler : IXEventHandler<XCreatePersonEvent> {
    private readonly IXEventBus eventBus;
    private ILogger<XCreatePersonEventHandler> logger;

    public XCreatePersonEventHandler (
        IXEventBus eventBus,
        ILoggerFactory loggerFactory
    ) {
        this.logger = loggerFactory.CreateLogger<XCreatePersonEventHandler> ();
        this.eventBus = eventBus;
    }

    public async Task HandleAsync (XCreatePersonEvent @event) {
        //
        logger.LogInformation ($"Received Event: {@event.ToJSON()}");

        //
        // Publish XPersonCreated Event ...
        var personCreatedEvent = new XPersonCreatedEvent (
            id: Guid.NewGuid (),
            firstname: @event.Firstname,
            lastname: @event.Lastname
        );

        //
        eventBus.Publish (personCreatedEvent);

        //
        await Task.CompletedTask;
    }
}

public class XPersonCreatedEventHandler : IXEventHandler<XPersonCreatedEvent> {
    private ILogger<XPersonCreatedEventHandler> logger;

    public XPersonCreatedEventHandler (ILoggerFactory loggerFactory) {
        this.logger = loggerFactory.CreateLogger<XPersonCreatedEventHandler> ();
    }

    public async Task HandleAsync (XPersonCreatedEvent @event) {
        //
        logger.LogInformation ($"Received Event: {@event.ToJSON()}");
        await Task.CompletedTask;
    }
}

and register your event handlers in Startup, like this:

...
public void ConfigureServices (IServiceCollection services) {
    ...
    //
    // Register Event Handlers ...
    services.AddXEventHandler<XCreatePersonEvent, XCreatePersonEventHandler> ();
    services.AddXEventHandler<XPersonCreatedEvent, XPersonCreatedEventHandler> ();

    //
    // Register Event Service ...
    services.AddXEventService (Configuration);
    ...
}
...

Subscribe

for each event you had to respond in yor project, after create related EventHandler, last step is subscribing to the event in IXEventBus implementation in Startup, like this:

...
public void Configure (IApplicationBuilder app, IWebHostEnvironment env) {
    ...
    //
    // Subscribe to Events ...
    app.XEventSubscribe<XCreatePersonEvent, XCreatePersonEventHandler> ();
    app.XEventSubscribe<XPersonCreatedEvent, XPersonCreatedEventHandler> ();
    ...
}

Maintainer

Hadi Khazaee asl

https://www.saherelm.ir

hadi_khazaee_asl@yahoo.com