提问人：Dominick 提问时间：4/23/2019 更新时间：9/17/2019 访问量：3063
覆盖 Owin 中间件中的响应正文
Overwrite Response Body in Owin Middleware
问：
我有一个正在使用的 Owin 中间件类。目的是在检测到 401、403 或 405 HTTP 状态代码时覆盖响应正文，并将正文替换为 JSON 对象。这是我到目前为止的方法：
public override async Task Invoke(IOwinContext context)
{
await Next.Invoke(context);
if (context.Response.StatusCode == 401 || context.Response.StatusCode == 403 || context.Response.StatusCode == 405)
{
var owinResponse = context.Response;
var owinResponseStream = owinResponse.Body;
var responseBuffer = new MemoryStream();
owinResponse.Body = responseBuffer;
string message;
switch (context.Response.StatusCode)
{
case 401:
message = "unauthorized request";
break;
case 403:
message = "forbidden request";
break;
default:
message = "request not allowed";
break;
}
var newResponse = new ResponseMessage<string>
{
IsError = true,
StatusCode = (HttpStatusCode) Enum.Parse(typeof(HttpStatusCode), context.Response.StatusCode.ToString()),
Data = null,
Message = message
};
var customResponseBody = new StringContent(JsonConvert.SerializeObject(newResponse));
var customResponseStream = await customResponseBody.ReadAsStreamAsync();
await customResponseStream.CopyToAsync(owinResponseStream);
owinResponse.ContentType = "application/json";
owinResponse.ContentLength = customResponseStream.Length;
owinResponse.StatusCode = 200;
owinResponse.Body = owinResponseStream;
}
}
在大多数情况下，它正在工作，但是响应正文被追加到而不是替换。例如，在 401 错误的情况下，响应正文为：
{"message":"Authorization has been denied for this request."}
{"IsError":true,"StatusCode":401,"Data":null,"Message":"unauthorized request"}
而不是：
{"IsError":true,"StatusCode":401,"Data":null,"Message":"unauthorized request"}
我确信这与我写给响应机构的方式有关，但到目前为止还没有解决问题。
任何建议将不胜感激。
谢谢
答：
1赞
M. Abouzeid
4/23/2019
#1
当您第一次将响应正文设置为内存流时，光标（当前位置）将移动到它的末尾。 ，结果，我们被存储了，光标指向最后。owinResponse.Body = responseBuffer;{"message":"Authorization has been denied for this request."}
同样，在方法的末尾，您编写包含消息的新响应owinResponse.Body = owinResponseStream;{"IsError":true,"StatusCode":401,"Data":null,"Message":"unauthorized request"}
由于当前位置指向流的末尾，因此它将附加。
尝试删除第一组正文 owinResponse.Body = responseBuffer;
3赞
Chingiz Humbatov
9/17/2019
#2
因为你在下面写代码await Next.Invoke(context);
await Next.Invoke(context);
if (context.Response.StatusCode == 401 || context.Response.StatusCode == 403 || context.Response.StatusCode == 405)
{
var owinResponse = context.Response;
var owinResponseStream = owinResponse.Body;
var responseBuffer = new MemoryStream();
owinResponse.Body = responseBuffer;
这是错误的。
下一个代码可以根据需要工作：
public override async Task Invoke(IOwinContext context)
{
var owinResponse = context.Response;
var owinResponseStream = owinResponse.Body;
var responseBuffer = new MemoryStream();
owinResponse.Body = responseBuffer;
await Next.Invoke(context);
if (context.Response.StatusCode == 401 || context.Response.StatusCode == 403 || context.Response.StatusCode == 405)
{
string message;
switch (context.Response.StatusCode)
{
case 401:
message = "unauthorized request";
break;
case 403:
message = "forbidden request";
break;
default:
message = "request not allowed";
break;
}
var newResponse = new ResponseMessage<string>
{
IsError = true,
StatusCode = (HttpStatusCode) Enum.Parse(typeof(HttpStatusCode), context.Response.StatusCode.ToString()),
Data = null,
Message = message
};
var customResponseBody = new StringContent(JsonConvert.SerializeObject(newResponse));
var customResponseStream = await customResponseBody.ReadAsStreamAsync();
await customResponseStream.CopyToAsync(owinResponseStream);
owinResponse.ContentType = "application/json";
owinResponse.ContentLength = customResponseStream.Length;
owinResponse.StatusCode = 200;
owinResponse.Body = owinResponseStream;
}
}
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