c# - WebAPI 强制反序列化不同于 Controller 方法中定义的对象

Question

我试图以这样一种方式引入自动映射器，即对于 WebAPI，所有 DTO 都是透明的，所以基本上我想在运行时映射对象，并在它们到达 Controller 方法之前将它们转换为域对象。

我有automapper过滤器属性

[AttributeUsage(AttributeTargets.Method, AllowMultiple = false)]
    public class AutoMapAttribute : ActionFilterAttribute
{
    private readonly Type _sourceType;
    private readonly Type _destType;

    public AutoMapAttribute(Type sourceType, Type destType)
    {
        _sourceType = sourceType;
        _destType = destType;
    }

    #region Overrides of ActionFilterAttribute

    /// <summary>Occurs before the action method is invoked.</summary>
    /// <param name="actionContext">The action context.</param>
    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        var mapper = ServiceLocator.Locator.GetInstance<IMapper>();
        var jsonObject = actionContext.ActionArguments.FirstOrDefault(x => x.Value.GetType() == typeof(Newtonsoft.Json.Linq.JObject));
        var dto = JsonConvert.DeserializeObject(jsonObject.Value.ToString(), _sourceType);
        object model = mapper.Map(dto, _sourceType, _destType);

        actionContext.ActionArguments[jsonObject.Key] = model;

        base.OnActionExecuting(actionContext);
    }

    #endregion

    #region Overrides of ActionFilterAttribute

    /// <summary>Occurs after the action method is invoked.</summary>
    /// <param name="actionExecutedContext">The action executed context.</param>
    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        base.OnActionExecuted(actionExecutedContext);
    }

    #endregion

    public Type SourceType
    {
        get { return _sourceType; }
    }

    public Type DestType
    {
        get { return _destType; }
    }
}

和 Controller 方法:

    [HttpPost]
    [Route("")]
    [AutoMap(typeof(Public.Dto.Product), typeof(Domain.Model.Product))]
    public IHttpActionResult Post(object product)
    {
        _productBusinessLogic.Create(product);
        return Ok();
    }

它工作得很好，因为 controlr 方法中的产品变量实际上是我的域产品。 现在我想在 Controller 方法定义中将对象类型更改为具体的 Domain.Product 类型。不幸的是，WebAPI 试图立即将来自 Request 的对象反序列化为该对象类型，这打破了整个想法。

如果有帮助，我可以使用 OWIN。

Answer 1

关键是 Action 过滤器的处理发生在模型绑定(bind)之后 Web API request stack .

使用 OWIN我们可以读取原始主体作为源类型，然后将其映射到目标类型:

1. 覆盖 OnActionExecutingAsync方法:

   public override async Task OnActionExecutingAsync(HttpActionContext actionContext,
       CancellationToken cancellationToken)
   {
       var argumentKey = actionContext.ActionArguments.FirstOrDefault().Key;
   
       var owinContext = (OwinContext) actionContext.Request.Properties["MS_OwinContext"];
   
       owinContext.Request.Body.Seek(0, SeekOrigin.Begin);
   
       var source = await actionContext.Request.Content.ReadAsAsync(_sourceType, cancellationToken);
   
       actionContext.ActionArguments[argumentKey] = Mapper.Map(source, _sourceType, _destType);
   
       await base.OnActionExecutingAsync(actionContext, cancellationToken);
   }
   

2. 要在操作过滤器中重新读取请求的内容，我们需要在 OWIN 中的管道中添加一些处理程序。启动类:

   public class Startup
   {
       public void Configuration(IAppBuilder app)
       {
           var config = new HttpConfiguration();
   
           app.Use(async (context, next) =>
           {
               var content = context.Request.Body;
   
               if (content == Stream.Null)
               {
                  await next();
               }
               else
               {
                   using (var stream = new MemoryStream())
                   {
                       await content.CopyToAsync(stream);
   
                       stream.Position = 0;
   
                       context.Request.Body = stream;
   
                       await next();
                   }
   
                   context.Request.Body = content;
               }
           });
   
           app.UseWebApi(config);        
       }
   }