本文為英文版的機器翻譯版本,如內容有任何歧義或不一致之處,概以英文版為準。
接收 Amazon SQS 訊息
此範例示範如何使用 AWS SDK for .NET 接收來自 Amazon SQS佇列的訊息,您可以透過程式設計或使用 Amazon SQS主控台
此範例和先前關於傳送訊息的範例可以一起使用,以查看 Amazon 中的訊息流程SQS。
下列各節提供此範例的程式碼片段。範例的完整程式碼在此之後顯示,並且可以像原樣建置和執行。
接收訊息
下列程式碼片段會從指定佇列 識別的佇列中收到訊息URL。
本主題結尾的範例顯示此程式碼片段正在使用中。
// // Method to read a message from the given queue // In this example, it gets one message at a time private static async Task<ReceiveMessageResponse> GetMessage( IAmazonSQS sqsClient, string qUrl, int waitTime=0) { return await sqsClient.ReceiveMessageAsync(new ReceiveMessageRequest{ QueueUrl=qUrl, MaxNumberOfMessages=MaxMessages, WaitTimeSeconds=waitTime // (Could also request attributes, set visibility timeout, etc.) }); }
刪除訊息
下列程式碼片段會從指定佇列 識別的佇列中刪除訊息URL。
本主題結尾的範例顯示此片段正在使用中。
// // Method to delete a message from a queue private static async Task DeleteMessage( IAmazonSQS sqsClient, Message message, string qUrl) { Console.WriteLine($"\nDeleting message {message.MessageId} from queue..."); await sqsClient.DeleteMessageAsync(qUrl, message.ReceiptHandle); }
完成程式碼
本節顯示此範例的相關參考和完整程式碼。
NuGet 套件:
程式設計元素:
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命名空間 Amazon。SQS
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命名空間 Amazon.SQS.模型
using System; using System.Threading.Tasks; using Amazon.SQS; using Amazon.SQS.Model; namespace SQSReceiveMessages { class Program { private const int MaxMessages = 1; private const int WaitTime = 2; static async Task Main(string[] args) { // Do some checks on the command-line if(args.Length == 0) { Console.WriteLine("\nUsage: SQSReceiveMessages queue_url"); Console.WriteLine(" queue_url - The URL of an existing SQS queue."); return; } if(!args[0].StartsWith("https://sqs.")) { Console.WriteLine("\nThe command-line argument isn't a queue URL:"); Console.WriteLine($"{args[0]}"); return; } // Create the Amazon SQS client var sqsClient = new AmazonSQSClient(); // (could verify that the queue exists) // Read messages from the queue and perform appropriate actions Console.WriteLine($"Reading messages from queue\n {args[0]}"); Console.WriteLine("Press any key to stop. (Response might be slightly delayed.)"); do { var msg = await GetMessage(sqsClient, args[0], WaitTime); if(msg.Messages.Count != 0) { if(ProcessMessage(msg.Messages[0])) await DeleteMessage(sqsClient, msg.Messages[0], args[0]); } } while(!Console.KeyAvailable); } // // Method to read a message from the given queue // In this example, it gets one message at a time private static async Task<ReceiveMessageResponse> GetMessage( IAmazonSQS sqsClient, string qUrl, int waitTime=0) { return await sqsClient.ReceiveMessageAsync(new ReceiveMessageRequest{ QueueUrl=qUrl, MaxNumberOfMessages=MaxMessages, WaitTimeSeconds=waitTime // (Could also request attributes, set visibility timeout, etc.) }); } // // Method to process a message // In this example, it simply prints the message private static bool ProcessMessage(Message message) { Console.WriteLine($"\nMessage body of {message.MessageId}:"); Console.WriteLine($"{message.Body}"); return true; } // // Method to delete a message from a queue private static async Task DeleteMessage( IAmazonSQS sqsClient, Message message, string qUrl) { Console.WriteLine($"\nDeleting message {message.MessageId} from queue..."); await sqsClient.DeleteMessageAsync(qUrl, message.ReceiptHandle); } } }
其他考量
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在訊息處理期間,您可以使用接收控點來變更訊息可見性逾時。如需如何執行此操作的詳細資訊,請參閱 AmazonSQSClient 類別
ChangeMessageVisibilityAsync
的方法。
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無論可見性逾時設定為何,無條件呼叫
DeleteMessageAsync
方法都會從佇列中移除訊息。