c# - 在 ASP.NET Web API 中抑制 JsonMediaTypeFormatter 的 RequiredAttribute 验证

Question

假设我向我的 API 发送了以下请求:

POST http://localhost:4940/api/cars HTTP/1.1
User-Agent: Fiddler
Host: localhost:4940
Content-Type: application/json
Content-Length: 44

{"Make":"Make1","Year":2010,"Price":10732.2}

我有以下 Car 类定义:

public class Car {

    public int Id { get; set; }

    [Required]
    [StringLength(20)]
    public string Make { get; set; }

    [Required]
    [StringLength(20)]
    public string Model { get; set; }

    public int Year { get; set; }

    [Range(0, 500000)]
    public float Price { get; set; }
}

我得到的回复如下:

HTTP/1.1 400 Bad Request
Cache-Control: no-cache
Pragma: no-cache
Content-Type: application/json; charset=utf-8
Expires: -1
Server: Microsoft-IIS/8.0
X-AspNet-Version: 4.0.30319
X-SourceFiles: =?UTF-8?B?RTpcRHJvcGJveFxCb29rc1xQcm9XZWJBUEkuU2FtcGxlc1xDaGFwdGVyMTNcRGF0YUFubm90YXRpb25WYWxpZGF0aW9uQXR0cmlidXRlc1NhbXBsZVxEYXRhQW5ub3RhdGlvblZhbGlkYXRpb25BdHRyaWJ1dGVzU2FtcGxlXGFwaVxjYXJz?=
X-Powered-By: ASP.NET
Date: Mon, 17 Sep 2012 11:38:58 GMT
Content-Length: 182

{"Message":"The request is invalid.","ModelState":{"car":["Required property 'Model' not found in JSON. Path '', line 1, position 44."],"car.Model":["The Model field is required."]}}

这是消息正文的更易读的形式:

{
    "Message": "The request is invalid.",
    "ModelState": {
        "car": [
            "Required property 'Model' not found in JSON. Path '', line 1, position 44."
        ],
        "car.Model":[
            "The Model field is required."
        ]
    }
}

如您所见，我还有一条关于 car 的额外错误消息，我猜测 JsonMediaTypeFormatter 也执行了验证，但未能执行读取操作。

这是这里的问题吗？有什么办法可以抑制 JsonMediaTypeFormatter 级别的验证吗？我不希望格式化程序执行验证，因为验证也是在格式化程序读取消息正文后由 IBodyModelValidator 执行的。

编辑:

我调试了源代码，它发现 JsonMediaTypeFormatter 在属性标记为必需但未提供时抛出错误。以下代码是 JsonMediaTypeFormatter 的一部分:

// Error must always be marked as handled
// Failure to do so can cause the exception to be rethrown at every recursive level and overflow the stack for x64 CLR processes
jsonSerializer.Error += (sender, e) =>
{
    Exception exception = e.ErrorContext.Error;
    formatterLogger.LogError(e.ErrorContext.Path, exception);
    e.ErrorContext.Handled = true;
}

这会触发 ModelStateFormatterLogger.LogError 方法，该方法将错误放入 ModelState 中:

public void LogError(string errorPath, Exception exception)
{
    if (errorPath == null)
    {
        throw Error.ArgumentNull("errorPath");
    }
    if (exception == null)
    {
        throw Error.ArgumentNull("exception");
    }

    string key = ModelBindingHelper.ConcatenateKeys(_prefix, errorPath);
    _modelState.AddModelError(key, exception);
}

我仍然无法抑制这种行为。

Answer 1

抱歉，我最初误解了您的问题。好的，这是您需要做的:

创建一个派生自原始 JsonMediaTypeFormatter 的类并设置自定义 IRequiredMemberSelector

public class MyJsonMediaTypeFormatter : JsonMediaTypeFormatter
    {
        public MyJsonMediaTypeFormatter() : base()
        {
            RequiredMemberSelector = new MyRequiredMemberSelector();
        }
    }

在此自定义 IRequiredMemberSelector 中，只需将所有属性定义为不需要。

public class MyRequiredMemberSelector : IRequiredMemberSelector
{
    public bool IsRequiredMember(System.Reflection.MemberInfo member)
    {
        return false;
    }
}

现在用自定义的替换默认的 JsonMediaTypeFormatter 就可以了。