如何将参数传递给 IEventProcessor 的实现答案

【问题标题】：How to pass parameters to an implementation of IEventProcessor如何将参数传递给 IEventProcessor 的实现
【发布时间】：2015-10-27 15:18:47
【问题描述】：

我正忙于为 azure EventBus 客户端实现 EventProcessorHost 客户端。

我有一个实现IEventProcessor 的类，如下所示：

 public class MyEventProcessor : IEventProcessor
    {
        Stopwatch checkpointStopWatch;            

        //TODO: get provider id from parent class     


        public async Task CloseAsync(PartitionContext context, CloseReason reason)
        {
            Debug.WriteLine("Processor Shutting Down. Partition '{0}', Reason: '{1}'.", context.Lease.PartitionId, reason);
            if (reason == CloseReason.Shutdown)
            {
                await context.CheckpointAsync();
            }
        }

        public Task OpenAsync(PartitionContext context)
        {
            Debug.WriteLine("SimpleEventProcessor initialized.  Partition: '{0}', Offset: '{1}'", context.Lease.PartitionId, context.Lease.Offset);
            eventHandler = new MyEventHandler();
            this.checkpointStopWatch = new Stopwatch();
            this.checkpointStopWatch.Start();
            return Task.FromResult<object>(null);
        }

        async Task IEventProcessor.ProcessEventsAsync(PartitionContext context, IEnumerable<EventData> messages)
        {
            foreach (EventData eventData in messages)
            {
                string data = Encoding.UTF8.GetString(eventData.GetBytes());              
                Debug.WriteLine(data);       
            }
            //Call checkpoint every 5 minutes, so that worker can resume processing from the 5 minutes back if it restarts.
            if (this.checkpointStopWatch.Elapsed > TimeSpan.FromMinutes(5))
            {
                await context.CheckpointAsync();
                this.checkpointStopWatch.Restart();
            }
        }
    }

然后我这样称呼它：

 EventProcessorHost _eventProcessorHost = new EventProcessorHost(eventProcessorHostName, EndpointName, EventHubConsumerGroup.DefaultGroupName, ConnectionString, storageConnectionString, "messages-events");
 await _eventProcessorHost.RegisterEventProcessorAsync<MyEventProcessor>();

我需要将一个参数传递给EventProcessorHost 创建的MyEventProcessor 实例。我该怎么做呢？

【问题讨论】：

标签： c# azure azure-eventhub event-processor-host

【解决方案1】：

您只需要使用RegisterEventProcessorFactoryAsync 来传递factory instance。该工厂类可以传入工厂方法中合适的任何参数，可能首先将它们传递给工厂，或者让工厂改变行为。在下面草绘的代码中，您可以看到两个参数被传递到IEventProcessor。其中一个来自工厂的参数，另一个是工厂被调用次数的计数器。

class AzureStreamProcessor : IEventProcessor
{
     ....
}

class AzureStreamProcessorFactory : IEventProcessorFactory
{
    public AzureStreamProcessorFactory(string str)
    {
         this.randomString = str;
    }

    private string randomString;
    private int numCreated = 0;
    IEventProcessor IEventProcessorFactory.CreateEventProcessor(PartitionContext context)
    {
        return new AzureStreamProcessor(context, randomString, Interlocked.Increment(ref numCreated));
    }
}

host.RegisterEventProcessorFactoryAsync(new AzureStreamProcessorFactory("a parameter"), options);

【讨论】：

这是要走的路！

【解决方案2】：

可以尝试使用如下参数对 MyEventProcessor 类进行构造函数依赖注入。

     public class MyEventProcessor : IEventProcessor
    {
        Stopwatch checkpointStopWatch;            

        //TODO: get provider id from parent class     
    IParameters _parameter;
    public MyEventProcessor (IParameters param)
    {
      this._parameter  = param;
     }

        public async Task CloseAsync(PartitionContext context, CloseReason reason)
        {
            Debug.WriteLine("Processor Shutting Down. Partition '{0}', Reason: '{1}'.", context.Lease.PartitionId, reason);
            if (reason == CloseReason.Shutdown)
            {
                await context.CheckpointAsync();
            }
        }.....

使用 _parameter 检索您需要的内容。

以下是您如何为您的 IParameters

注册依赖项

这里我使用 Ninject 依赖解析器。

//Bind the class that implements IParameter.
 var parameters = new Parameter();
paramters.Property = "my data"

 kernel.Bind<IParameters>().ToConstant(parameters);

希望对你有帮助

【讨论】：