CQRS與AutoMapper或Mapster(六)
呈上篇，我們已經將驗證透過IPipelineBehavior進行簡化了，以下是目前的程式碼
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[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
private readonly IMediator _mediator;
public WeatherForecastController(IMediator mediator)
{
_mediator = mediator;
}
[HttpPost]
public async Task<IActionResult> CreateWeatherForecast(
[FromBody] CreateWeatherForecastRequest request)
{
var command = new CreateWeatherForecastCommand
{
Nation = request.Nation,
City = request.City,
Date = request.Date,
TemperatureC = request.TemperatureC,
Summary = request.Summary,
};
var result = await _mediator.Send(command);
return result ? Ok() : BadRequest();
}
[HttpPut("{id:int}")]
public async Task<IActionResult> UpdateWeatherForecast(int id,
[FromBody] UpdateWeatherForecastRequest request)
{
if (id != request.WeatherForecastId) return BadRequest();
var command = new UpdateWeatherForecastCommand
{
WeatherForecastId = request.WeatherForecastId,
Nation = request.Nation,
City = request.City,
Date = request.Date,
TemperatureC = request.TemperatureC,
Summary = request.Summary,
};
var result = await _mediator.Send(command);
return result ? Ok() : BadRequest();
}
}
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其中我們可以看到CreateWeatherForecastRequest與CreateWeatherForecastCommand，兩個類別高度重複
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// CreateWeatherForecastRequest.cs 類別
public class CreateWeatherForecastRequest
{
public string Nation { get; set; }
public string City { get; set; }
public DateTime Date { get; set; }
public int TemperatureC { get; set; }
public string Summary { get; set; }
}
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// CreateWeatherForecastCommand.cs 類別
public class CreateWeatherForecastCommand : ICommand<bool>
{
public string Nation { get; set; } = string.Empty;
public string City { get; set; } = string.Empty;
public DateTime Date { get; set; }
public int TemperatureC { get; set; }
public string? Summary { get; set; }
}
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有部分範例會直接使用 Command 取代 Request，但這會造成高層元件依賴低層。當然在簡單的專案上，是否需要完整切割，還是看個人與團隊的共識，減少類別與簡化實作也是一個選擇。
而本篇介紹另一個套件，AutoMapper，該套件已經存在數十年之久，也有相當多的專案採用與文章介紹，前幾篇有提到 AutoMapper 和 MediatR 均是出自 Jimmy Bogard 這位大神的手中，深遠的影響著大大小小的專案，該作者的Blog，也提出相當多，值得學習的觀點，包括 Repository 層是否實作的爭議。
由於相關介紹文章已經很多了，這邊只快速帶過，介紹導入步驟。
環境
- AutoMapper.Extensions.Microsoft.DependencyInjection
官方告知從版本 13.0 開始，AddAutoMapper成為核心包的一部分，並且 DI 套件將停止使用。然而寫這篇的時候，最新版本為 12.0.1，所以我們還是安裝了AutoMapper.Extensions.Microsoft.DependencyInjection，才能使用AddAutoMapper
安裝 AutoMapper
新增 Profile 實例
個人習慣會開一個 Mappers 資料夾，然後設定一個AutoMappers空類別，內部依照類別+Profile命名。
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public class AutoMappers
{
}
public class WeatherForecastProfile : Profile
{
public WeatherForecastProfile()
{
CreateMap<CreateWeatherForecastRequest, CreateWeatherForecastCommand>();
CreateMap<UpdateWeatherForecastRequest, UpdateWeatherForecastCommand>();
}
}
// 其他類別的 Mapper Instances
//public class LocationProfile : Profile
//{
// public LocationProfile()
// {
// CreateMap<TSourece,TDestination> ...
// }
//}
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在IServiceCollection註冊
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builder.Services.AddAutoMapper(typeof(AutoMappers));
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Controller引用IMapper
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[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
private readonly IMediator _mediator;
private readonly IMapper _mapper;
// 1.使用IMapper
public WeatherForecastController(IMediator mediator, IMapper mapper)
{
_mediator = mediator;
_mapper = mapper;
}
[HttpPost]
public async Task<IActionResult> CreateWeatherForecast(
[FromBody] CreateWeatherForecastRequest request)
{
// 2.轉換型別
var command = _mapper.Map<CreateWeatherForecastCommand>(request);
var result = await _mediator.Send(command);
return result ? Ok() : BadRequest();
}
[HttpPut("{id:int}")]
public async Task<IActionResult> UpdateWeatherForecast(int id,
[FromBody] UpdateWeatherForecastRequest request)
{
if (id != request.WeatherForecastId) return BadRequest();
var command = _mapper.Map<UpdateWeatherForecastCommand>(request);
var result = await _mediator.Send(command);
return result ? Ok() : BadRequest();
}
}
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同場加映 Mapster
Mapster，也是一款物件自動對應工具，與 AutoMapper 功能相似，速度更快、檔案更小且更易用的選擇。
安裝 Mapster
物件轉換
如果是兩個屬性名稱相同的物件轉換，則在來源物件上直接使用Adapt即可，不需要額外設定，也不需要建構子注入，就是這麼簡單易用。
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[ApiController]
[Route("[controller]")]
public class WeatherForecastController : ControllerBase
{
private readonly IMediator _mediator;
public WeatherForecastController(IMediator mediator)
{
_mediator = mediator;
}
[Authorize]
[HttpGet]
public async Task<IActionResult> GetWeatherForecasts([FromQuery] GetWeatherForecastsQuery request)
{
var query = await _mediator.Send(request);
return Ok(query);
}
[HttpPost]
public async Task<IActionResult> CreateWeatherForecast([FromBody] CreateWeatherForecastRequest request)
{
// Mapster屬性名稱相同，可直接對應
var command = request.Adapt<CreateWeatherForecastCommand>();
var result = await _mediator.Send(command);
return result ? Ok() : BadRequest();
}
[HttpPut("{id:int}")]
public async Task<IActionResult> UpdateWeatherForecast(int id, [FromBody] UpdateWeatherForecastRequest request)
{
if (id != request.WeatherForecastId) return BadRequest();
var command = request.Adapt<UpdateWeatherForecastCommand>();
var result = await _mediator.Send(command);
return result ? Ok() : BadRequest();
}
}
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參考
放棄 AutoMapper ，擁抱 Mapster
https://www.twblogs.net/a/61dd1d25fd6fbb767a0d57cc
使用 Mapster 處理物件對應
https://www.dotblogs.com.tw/Null/2020/03/23/221949
結論
經過一系列的簡化，Controller 程式碼已經大幅減少，變得精簡，使用者呼叫Api，Api 透過 MediatR調用請求，而應用服務(Applicatoin)層再將主要邏輯，交由領域(Domain)層來處理，形成各式各樣的微服務(Microservices)。
這種以領域層為中心、由外而內，透過聚合根(Aggregate Root)來執行主要邏輯，是一種 Clean Achitecture 架構，然而就如第一篇文章所說，系列文章沒有涉及 DDD 議題，僅記錄大致的架構分層與 MediatR 的使用。
