Question

我有一个简单的控制器动作，如下所示：

    public Task<IEnumerable<Data>> GetData()
    {
        IEnumerable<Data> data = new List<Data>();
        return data;
    }

我希望能够从中间件中检查返回值，以便JSON看起来像

{
  "data": [
  ],
  "apiVersion": "1.2",
  "otherInfoHere": "here"
}

所以我的有效负载总是在data之内。我知道我可以在控制器级别这样做，但我不想在每一个动作上都这样做。我宁愿一次性在中间件中做这件事。

以下是我的中间件示例：

public class NormalResponseWrapper
{
    private readonly RequestDelegate next;

    public NormalResponseWrapper(RequestDelegate next)
    {
        this.next = next;
    }

    public async Task Invoke(HttpContext context)
    {                
        var obj = context;
        // DO something to get return value from obj
        // Create payload and set data to return value

        await context.Response.WriteAsync(/*RETURN NEW PAYLOAD HERE*/);
    }

有什么想法吗？

现在有了价值，但要归还它

        try
        {
            using (var memStream = new MemoryStream())
            {
                context.Response.Body = memStream;
                await next(context);
                memStream.Position = 0;
                object responseBody = new StreamReader(memStream).ReadToEnd();
                memStream.Position = 0;
                await memStream.CopyToAsync(originalBody);
                // By now it is to late, above line sets the value that is going to be returned
                await context.Response.WriteAsync(new BaseResponse() { data = responseBody }.toJson());
            }

        }
        finally
        {
            context.Response.Body = originalBody;
        }

Answer 1

查看评论，以了解如何包装回复。

public async Task Invoke(HttpContext context) {
    //Hold on to original body for downstream calls
    Stream originalBody = context.Response.Body;
    try {
        string responseBody = null;
        using (var memStream = new MemoryStream()) {
            //Replace stream for upstream calls.
            context.Response.Body = memStream;
            //continue up the pipeline
            await next(context);
            //back from upstream call.
            //memory stream now hold the response data
            //reset position to read data stored in response stream
            memStream.Position = 0;
            responseBody = new StreamReader(memStream).ReadToEnd();
        }//dispose of previous memory stream.
        //lets convert responseBody to something we can use
        var data = JsonConvert.DeserializeObject(responseBody);
        //create your wrapper response and convert to JSON
        var json = new BaseResponse() { 
            data = data, 
            apiVersion = "1.2",
            otherInfoHere = "here"
        }.toJson();
        //convert json to a stream
        var buffer = Encoding.UTF8.GetBytes(json);
        using(var output = new MemoryStream(buffer)) {
            await output.CopyToAsync(originalBody);
        }//dispose of output stream
    } finally {
        //and finally, reset the stream for downstream calls
        context.Response.Body = originalBody;
    }
}

Answer 2

在.NET Core 3.1或.NET 5中

创建响应信封对象。示例：

internal class ResponseEnvelope<T>
{
  public T Data { set; get; }
  public string ApiVersion { set; get; }
  public string OtherInfoHere { set; get; }
}

从ObjectResultExecutor派生一个类

internal class ResponseEnvelopeResultExecutor : ObjectResultExecutor
{
 public ResponseEnvelopeResultExecutor(OutputFormatterSelector formatterSelector, IHttpResponseStreamWriterFactory writerFactory, ILoggerFactory loggerFactory, IOptions<MvcOptions> mvcOptions) : base(formatterSelector, writerFactory, loggerFactory, mvcOptions)
 {
 }

 public override Task ExecuteAsync(ActionContext context, ObjectResult result)
 {
     var response = new ResponseEnvelope<object>();
     response.Data = result.Value;
     response.ApiVersion = "v1";
     response.OtherInfoHere = "OtherInfo";

     TypeCode typeCode = Type.GetTypeCode(result.Value.GetType());
     if (typeCode == TypeCode.Object)
          result.Value = response;

     return base.ExecuteAsync(context, result);
  }
}

像这样注入DI

public void ConfigureServices(IServiceCollection services)
 {
     services.AddSingleton<IActionResultExecutor<ObjectResult>, ResponseEnvelopeResultExecutor>();

并且回复中应该有一个信封。这不适用于基本类型。

C＃DotNet核心中间件包裹响应

2 个答案: