自定义验证错误的自动响应

在 asp.net core 2.1 中，当发生验证错误时，ApiController 将自动响应 400 BadRequest。

如何更改/修改发送回客户端的响应（json-body）？有某种中间件吗？

我正在使用 FluentValidation 来验证发送到控制器的参数，但我对得到的响应不满意。看起来像

{
    "Url": [
        "'Url' must not be empty.",
        "'Url' should not be empty."
    ]
}

我想更改响应，因为我们有一些附加到响应的默认值。所以它应该看起来像

{
    "code": 400,
    "request_id": "dfdfddf",
    "messages": [
        "'Url' must not be empty.",
        "'Url' should not be empty."
    ]
}

The ApiBehaviorOptions https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.apibehavioroptions?view=aspnetcore-2.1类允许生成ModelState通过其定制响应InvalidModelStateResponseFactory https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.apibehavioroptions.invalidmodelstateresponsefactory?view=aspnetcore-2.1#Microsoft_AspNetCore_Mvc_ApiBehaviorOptions_InvalidModelStateResponseFactory属性，其类型为Func<ActionContext, IActionResult>.

这是一个示例实现：

apiBehaviorOptions.InvalidModelStateResponseFactory = actionContext => {
    return new BadRequestObjectResult(new {
        Code = 400,
        Request_Id = "dfdfddf",
        Messages = actionContext.ModelState.Values.SelectMany(x => x.Errors)
            .Select(x => x.ErrorMessage)
    });
};

传入的ActionContext https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.actioncontext?view=aspnetcore-2.1实例同时提供ModelState https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.actioncontext.modelstate?view=aspnetcore-2.1#Microsoft_AspNetCore_Mvc_ActionContext_ModelState and HttpContext https://learn.microsoft.com/en-us/dotnet/api/microsoft.aspnetcore.mvc.actioncontext.httpcontext?view=aspnetcore-2.1#Microsoft_AspNetCore_Mvc_ActionContext_HttpContext活动请求的属性，其中包含我期望您可能需要的所有内容。我不确定你在哪里request_id值来自，所以我将其作为静态示例。

要使用此实现，请配置ApiBehaviorOptions实例在ConfigureServices:

serviceCollection.Configure<ApiBehaviorOptions>(apiBehaviorOptions =>
    apiBehaviorOptions.InvalidModelStateResponseFactory = ...
);