.net core使用EasyNetQ做EventBus

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随着SOA、微服务、CQRS的盛行，EventBus越来越流行，上GitHub搜了一下，还是有蛮多的这类实现，老牌的有NServiceBus（收费）、MassTransit，最近的有CAP（国人写的，1.4k个Star，非常不错）、ReBus（张队长在NanoFabric中推荐的）、RawRabbit等，今天我介绍的是另外一款产品：EasyNetQ，支持.net core，正如其名，用起来确实very easy。

首先在asp.net core项目中添加EasyNetQ的nuget引用，注入：

public void ConfigureServices(IServiceCollection services)
{
       string rabbitMqConnection = Configuration["RabbitMqConnection"];
       services.AddSingleton(RabbitHutch.CreateBus(rabbitMqConnection));
}

1、发布消息：

public class ValuesController : Controller
    {
        private IBus _bus;
        public ValuesController(IBus bus)
        {
            _bus = bus;
        }
    </span><span style="color: #008000;">//</span><span style="color: #008000;"> POST api/values</span>

        [HttpPost]

public async Task Post([FromBody]Order message)

{

await _bus.PublishAsync(message);

}

}

可自定义消息的Exchange和Queue，需要修改消息实体：

    [Queue("Qka.Order", ExchangeName = "Qka.Order")]
    public class Order
    {
        public int OrderId { get; set; }
    }

2、订阅消息

　　　我们订阅的服务也是寄宿在asp.net core程序中，首先定义消费者：

    public class OrderConsumer : IConsume<Order>
    {
        [AutoSubscriberConsumer(SubscriptionId = "OrderService")]
        public void Consume(Order message)
        {
            //业务代码
        }
    }

也可以使用异步方法：　　

    public class OrderConsumer : IConsumeAsync<Order>
    {
        [AutoSubscriberConsumer(SubscriptionId = "OrderService")]
        public Task ConsumeAsync(Order message)
        {
            //业务代码
        }
    }

　利用EasyNetQ的自动订阅者进行订阅，这里扩展IApplicationBuilder：

public static class ApplicationExtenssion
{
        public static IApplicationBuilder UseSubscribe(this IApplicationBuilder appBuilder, string subscriptionIdPrefix, Assembly assembly)
        {
            var services = appBuilder.ApplicationServices.CreateScope().ServiceProvider;
        </span><span style="color: #0000ff;">var</span> lifeTime = services.GetService&lt;IApplicationLifetime&gt;<span style="color: #000000;">();
        </span><span style="color: #0000ff;">var</span> bus = services.GetService&lt;IBus&gt;<span style="color: #000000;">();
        lifeTime.ApplicationStarted.Register(() </span>=&gt;<span style="color: #000000;">
        {
            </span><span style="color: #0000ff;">var</span> subscriber = <span style="color: #0000ff;">new</span><span style="color: #000000;"> AutoSubscriber(bus, subscriptionIdPrefix);
            subscriber.Subscribe(assembly);　　　　　　　　　<br></span>                subscriber.SubscribeAsync(assembly);<br><span>             }); <br><br>　　　　　　　　lifeTime.ApplicationStopped.Register(() </span>=&gt;<span> { bus.Dispose(); }); <br><br></span><span style="color: #0000ff;">　　　　　　　　return</span><span> appBuilder; <br>　　　　 } <br>}</span></pre>

使用扩展方法：

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            app.UseSubscribe("OrderService", Assembly.GetExecutingAssembly());
        }