返回文件的Web Api控制器的自动重发/切换生成代码

Question

在我的ASP.NET Web API应用程序中，我有一个这样的控制器:

    [RoutePrefix("api/ratings")]
    public class RateCostumerController : ApiController
    { 

        [AllowAnonymous]  
        [Route("Report/GetReport")]  
        [HttpGet]
        public HttpResponseMessage ExportReport([FromUri] string costumer)  

        {  
            var rd = new ReportDocument();  

           /*No relevant code here*/

            var result = new HttpResponseMessage(HttpStatusCode.OK)
            {
                Content = new ByteArrayContent(ms.ToArray())
            };
            result.Content.Headers.ContentDisposition =
                new System.Net.Http.Headers.ContentDispositionHeaderValue("attachment")
                {
                    FileName = "Reporte.pdf"
                };
            result.Content.Headers.ContentType =
                new MediaTypeHeaderValue("application/octet-stream");

            return result;
        }
}

因此，当我使用客户参数发出简单的GET请求时，我会在浏览器中获得一个pdf文件作为响应。一些响应标头：

内容配置：附件；filename=Reporte。pdf属性长度：22331属性类型：应用程序/八位字节流

设置 swagger 后，在我的 Xamarin PCL 项目中生成 json 元文件并生成 C# 代码，我尝试使用该服务。但它失败了，因为在生成的代码中试图反序列化json，但不是json结果！

在这里，它是生成的代码的一部分，它失败了：

[...]
var _result = new Microsoft.Rest.HttpOperationResponse<object>();
            _result.Request = _httpRequest;
            _result.Response = _httpResponse;
            // Deserialize Response
            if ((int)_statusCode == 200)
            {
                _responseContent = await _httpResponse.Content.ReadAsStringAsync().ConfigureAwait(false);
                try
                {
                    _result.Body = Microsoft.Rest.Serialization.SafeJsonConvert.DeserializeObject<object>(_responseContent, this.Client.DeserializationSettings);
                }
                catch (Newtonsoft.Json.JsonException ex)
                {
                    _httpRequest.Dispose();
                    if (_httpResponse != null)
                    {
                        _httpResponse.Dispose();
                    }
                    throw new Microsoft.Rest.SerializationException("Unable to deserialize the response.", _responseContent, ex);
                }
            }
            if (_shouldTrace)
            {
                Microsoft.Rest.ServiceClientTracing.Exit(_invocationId, _result);
            }
            return _result;
[...]

当我调试时，我发现文件的内容在主体中，所以反序列化会把它搞乱。由于不建议编辑此生成的类文件，我需要在API中进行哪些更改，以正确生成应用程序/八位字节流内容响应的代码？

Answer 1

对于Swashbuckle版本4，我创建过滤器:

public class FileDownloadOperation : IOperationFilter
{
    public void Apply(Operation operation, OperationFilterContext context)
    {
        var rt = context.MethodInfo.ReturnType;
        if (rt == typeof(Stream) || 
            rt == typeof(Task<Stream>) || 
            rt == typeof(FileStreamResult) || 
            rt == typeof(Task<FileStreamResult>))
        {
            operation.Responses["200"] = new Response
            {
                Description = "Success", Schema = new Schema {Type = "file"}
            };
            operation.Produces.Clear();
            operation.Produces.Add("application/octet-stream");
        }
    }
}

将其分配到摇摆发电机中

services.AddSwaggerGen(c =>
            {
                ...
                c.OperationFilter<FileDownloadOperation>();
            });

然后只需使用简单的控制器：

[HttpGet("{fileId}")]
public async Task<FileStreamResult> GetMyFile(int fileId)
{
    var result = await _fileService.GetFile(fileId);
    return File(result.Stream, result.ContentType, result.FileName);
}

Answer 2

生成的代码将方法的输出视为 json，因为错误的类型写入了 swagger.json（可能是 .... #/definitions/....）。它应该包含“类型”：“文件”

您可以使用SwaggerGen选项来操作输出。

如果您的方法如下所示：

    [Produces("application/pdf")]
    [ProducesResponseType(200, Type = typeof(Stream))]
    public IActionResult Download()
    {           
        Stream yourFileStream = null; //get file contents here
        return new FileStreamResult(yourFileStream , new MediaTypeHeaderValue("application/pdf"))
        {
            FileDownloadName = filename
        };
    }

在您的启动中，设置Swagger生成，配置您要返回的Type与您要出现在Swagger文件中的Type之间的映射

     services.AddSwaggerGen(
            options =>
            {                   
                options.MapType<System.IO.Stream>(() => new Schema { Type = "file" });
            });

那么您生成的代码如下所示:

public async Task<HttpOperationResponse<System.IO.Stream>> DownloadWithHttpMessagesAsync()

Answer 3

创建返回文件的自定义筛选器：

 [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false)]
    public sealed class SwaggerFileResponseAttribute : SwaggerResponseAttribute
    {
        public SwaggerFileResponseAttribute(HttpStatusCode statusCode) : base(statusCode)
        {
        }

        public SwaggerFileResponseAttribute(HttpStatusCode statusCode, string description = null, Type type = null)  : base(statusCode, description, type)
        {
        }
        public SwaggerFileResponseAttribute(int statusCode) : base(statusCode)
        {
        }

        public SwaggerFileResponseAttribute(int statusCode, string description = null, Type type = null) : base(statusCode, description, type)
        {
        }
    }

还有这个自定义的ResponseTypeFilter类:

public sealed class UpdateFileResponseTypeFilter : IOperationFilter
    {
        public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
        {
            if (apiDescription.GetControllerAndActionAttributes<SwaggerResponseRemoveDefaultsAttribute>().Any())
            {
                operation.responses.Clear();
            }
            var responseAttributes = apiDescription.GetControllerAndActionAttributes<SwaggerFileResponseAttribute>()
                .OrderBy(attr => attr.StatusCode);

            foreach (var attr in responseAttributes)
            {
                var statusCode = attr.StatusCode.ToString();

                Schema responseSchema = new Schema { format = "byte", type = "file" };

                operation.produces.Clear();
                operation.produces.Add("application/octet-stream");

                operation.responses[statusCode] = new Response
                {
                    description = attr.Description ?? InferDescriptionFrom(statusCode),
                    schema = responseSchema
                };
            }
        }

        private string InferDescriptionFrom(string statusCode)
        {
            HttpStatusCode enumValue;
            if (Enum.TryParse(statusCode, true, out enumValue))
            {
                return enumValue.ToString();
            }
            return null;
        }
    }

然后在 SwaggerConfig 文件中注册它：

c.OperationFilter<UpdateFileResponseTypeFilter>();

要使用此筛选器，只需将其添加到每个操作控制器中，如下所示：

 [Route("Report/GetReport/{folio}")]
        [SwaggerFileResponse(HttpStatusCode.OK, "File Response")]
        [HttpGet]
        public HttpResponseMessage ExportReport(string folio)
        {
...

因此，当swagger生成json元数据时，autorest将正确地创建一个返回任务的方法