用CAP操作RabbitMQ 处理分布式事务的解决方案

一、在Nuget中引用以下包：

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dotnetcore.cap DotNetCore.CAP.Dashboard DotNetCore.CAP.RabbitMQ DotNetCore.CAP.SqlServer

二、在Program.cs中注册服务

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//配置CAP builder.Services.AddCap(x => {     x.UseEntityFramework<AppDbContext>();//从AppDbContext获取数据库连接字符串     x.UseRabbitMQ("localhost");<br>　　x.DefaultGroupName = "cap.queue.app";//默认组名称     // Register Dashboard     x.UseDashboard(); //使用仪表盘，默认网址：http://localhost:当前网站端口/cap     //x.UseDashboard(opt => { opt.PathMatch = "/mycap"; });//配置仪表盘为新的网址     // Register to Consul     x.UseDiscovery(d =>     {         d.DiscoveryServerHostName = "localhost";         d.DiscoveryServerPort = 8500;         d.CurrentNodeHostName = "localhost";         d.CurrentNodePort = 5800;         d.NodeId = 1.ToString();         d.NodeName = "CAP No.1 Node";     }); });

三、发布消息

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using CAPWebApplication.Entities; using DotNetCore.CAP; using Microsoft.AspNetCore.Http; using Microsoft.AspNetCore.Mvc; using Microsoft.Data.SqlClient; using Microsoft.EntityFrameworkCore;   namespace CAPWebApplication.Controllers {       [Route("api/[controller]")]     [ApiController]     public class PublishController : ControllerBase     {         private readonly ILogger<PublishController> _logger;         private readonly ICapPublisher _capPublisher;         private readonly AppDbContext _dbContext;           public PublishController(ILogger<PublishController> logger, ICapPublisher capPublisher, AppDbContext dbContext)         {             _logger = logger;             _capPublisher = capPublisher;             _dbContext = dbContext;         }         //发送消息         [HttpGet("send")]         public async Task<ActionResult> SendMessage()         {//发布无事务的消息，消息重要性低时可以使用             await _capPublisher.PublishAsync("test.show.time", DateTime.Now);             return Ok();         }           [HttpGet("sendheader")]         public async Task SendHeaderMessage()         {//发布带有包头的消息             var header = new Dictionary<string, string>             {                 ["my.header.first"] = "first",                 ["my.header.second"] = "second"             };             _capPublisher.Publish("test.show.time", DateTime.Now, header);         }         [Route("adonet/transaction")]         [HttpGet]         public async Task AdonetWithTransaction()         {//ADO.NET 事务处理 操作数据库并且发送消息             using (var conn = new SqlConnection(_dbContext.Database.GetConnectionString()))             {                 using (var trans = conn.BeginTransaction(_capPublisher))                 {                       await _capPublisher.PublishAsync("test.order", DateTime.Now);                     trans.Commit();                 }             }         }         [Route("efcore/transaction")]         [HttpGet]         public async Task EfcoreWithTransaction()         {//EFCore 事件处理 操作数据库并且发送消息             using (var trans = _dbContext.Database.BeginTransaction(_capPublisher))             {                 Order order = new Order { Name = "赵六", Address = "湖南岳阳临湘" };                 _dbContext.Add(order);                 await _dbContext.SaveChangesAsync();                 await _capPublisher.PublishAsync("test.order", order);                 await trans.CommitAsync();             }         }       } }

四、订阅消息　

4.1 在控制器中订阅消息

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using CAPWebApplication.Entities; using DotNetCore.CAP; using Microsoft.AspNetCore.Http; using Microsoft.AspNetCore.Mvc; using Newtonsoft.Json;   namespace CAPWebApplication.Controllers {     [Route("api/[controller]")]     [ApiController]     public class ConsumerController : ControllerBase     {         //private readonly ILogger _logger;         //public ConsumerController(ILogger logger)         //{         //    _logger = logger;         //}         //[NonAction]         //[CapSubscribe("test.show.time")]         //public async Task ReceiveMessage(DateTime time)         //{         //    Console.WriteLine($"接收到的时间 :{time}");         //}         [NonAction]         [CapSubscribe("test.show.time")]         public async Task ReceiveHeaderMessage(DateTime time, [FromCap] CapHeader header)         {             Console.WriteLine($"接收到的时间：{time}");             Console.WriteLine($"第一个头部：{header["my.header.first"]}");             Console.WriteLine($"第二个头部：{header["my.header.second"]}");         }         [NonAction]         [CapSubscribe("test.order")]         public async Task CheckReceivedMessage(Order order)         {             //string msg= System.Text.Json.JsonSerializer.Serialize(order);             Console.WriteLine($"接受来自[test.order]的订单：{order}");         }     } }

　4.2 在业务逻辑订阅消息

如果你的订阅方法不在Controller中，那么你的订阅类需要实现ICapSubscribe接口：

 

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using CAPWebApplication.Entities; using DotNetCore.CAP;   namespace CAPWebApplication.BusinessCode {     public interface ISubscriberService     {         void CheckReceivedMessage(Order order);     }       public class SubscriberService : ISubscriberService, ICapSubscribe     {         [CapSubscribe("test.order")]         public void CheckReceivedMessage(Order order)         {             Console.WriteLine($"来自业务层的订阅：{order}");         }     } }

然后在Program.cs中注册ISubscriberService

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1	builder.Services.AddTransient<ISubscriberService, SubscriberService>();

注意：注册必须放在配置CAP之前，即 builder.Services.AddCap() 之前

 

五、组订阅

同一消息在同一个组里面只有一订阅能收到消息，但在不同的组多个订阅都能收到消息。

订阅组的概念类似于 Kafka 中的消费者组。与消息队列中的广播方式相同，用于处理多个不同微服务实例之间的同一条消息。

CAP 启动时，会使用当前的程序集名称作为默认的组名，如果多个同组订阅者订阅同一个主题名，则只有一个订阅者可以接收到消息。相反，如果订阅者在不同的组中，他们都会收到消息。

在同一个应用程序中，您可以指定Group属性以将订阅保存在不同的订阅组中：

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using CAPWebApplication.Entities; using DotNetCore.CAP;   namespace CAPWebApplication.BusinessCode {     public interface ISubscriberService     {         void CheckReceivedMessage(Order order);         void CheckReceivedMessage2(Order order);         void CheckReceivedMessage3(Order order);     }       public class SubscriberService : ISubscriberService, ICapSubscribe     {         [CapSubscribe("test.order")]         public void CheckReceivedMessage(Order order)         {             Console.WriteLine($"来自业务层的订阅：{order}");         }         [CapSubscribe("test.order",Group ="group1")]         public void CheckReceivedMessage2(Order order)         {             Console.WriteLine($"来自业务层group1的订阅：{order}");         }         [CapSubscribe("test.order",Group ="group2")]         public void CheckReceivedMessage3(Order order)         {             Console.WriteLine($"来自业务层group2的订阅：{order}");         }     } }

三个订阅都能收到同一消息

 六、主题订阅

将类上的订阅键+方法上的订阅键，最终组合在一起

实际的订阅键为：[CapSubscribe("test.order")]

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[CapSubscribe("test")]    [Route("api/[controller]")]    [ApiController]    public class ConsumerController : ControllerBase    {        [NonAction]        [CapSubscribe("order")]        public async Task CheckReceivedMessage(Order order)        {            //string msg= System.Text.Json.JsonSerializer.Serialize(order);            Console.WriteLine($"来自控制器的订阅消息：{order}");        }    }