基于 Accept 标头的 ASP.NET Core web api 操作选择

问题描述

我想根据请求的接受标头为同一功能(实体列表)返回两种不同格式的响应，这是针对json"和html"请求的.

I want to return two different formatted responses for the same feature (a list of entities) based on the accept header of the request, it is for a "json" and a "html" request.

asp.net 核心是否支持根据请求中的接受标头为同一路由选择不同的操作?

Does the asp.net core support select different actions for the same route based upon the Accept Header from the request?

推荐答案

我深入研究了 .net 核心源代码并寻找了其他具有类似行为的属性，例如 Microsoft.AspNetCore.Mvc.HttpGetcode> 或 Microsoft.AspNetCore.Mvc.ProducesAttribute.这两个属性都实现了一个 Microsoft.AspNetCore.Mvc.ActionConstraints.IActionConstraint 接口，aspnetcore.mvc 使用该接口来控制控制器内的动作选择.

I dived into the .net core source code and looked for other attributes that do some similar behaviour such as Microsoft.AspNetCore.Mvc.HttpGet or Microsoft.AspNetCore.Mvc.ProducesAttribute.Both attributes implements an Microsoft.AspNetCore.Mvc.ActionConstraints.IActionConstraint interface wich is used by aspnetcore.mvc to control the selection of actions inside a controller.

所以我实现了一个简化的 ProducesAttribute(一个贡品")来检查接受标头.

So i implemented a simplified ProducesAttribute (a "tribute") to check for the accept header.

    /// <summary>
    /// A filter that specifies the supported response content types. The request accept header is used to determine if it is a valid action
    /// </summary>
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public class AcceptHeaderAttribute : Attribute, IActionConstraint
    {

        public AcceptHeaderAttribute(string contentType, params string[] otherContentTypes)
        {
            if (contentType == null)
                throw new ArgumentNullException(nameof(contentType));

            // We want to ensure that the given provided content types are valid values, so
            // we validate them using the semantics of MediaTypeHeaderValue.
            MediaTypeHeaderValue.Parse(contentType);

            for (var i = 0; i < otherContentTypes.Length; i++)
            {
                MediaTypeHeaderValue.Parse(otherContentTypes[i]);
            }

            ContentTypes = GetContentTypes(contentType, otherContentTypes);
        }

        public MediaTypeCollection ContentTypes
        {
            get; set;
        }

        public int Order
        {
            get
            {
                return 0;
            }
        }

        private bool IsSubsetOfAnyContentType(string requestMediaType)
        {
            var parsedRequestMediaType = new MediaType(requestMediaType);
            for (var i = 0; i < ContentTypes.Count; i++)
            {
                var contentTypeMediaType = new MediaType(ContentTypes[i]);
                if (parsedRequestMediaType.IsSubsetOf(contentTypeMediaType))
                {
                    return true;
                }
            }
            return false;
        }

        public bool Accept(ActionConstraintContext context)
        {
            var requestAccept = context.RouteContext.HttpContext.Request.Headers[HeaderNames.Accept];
            if (StringValues.IsNullOrEmpty(requestAccept))
                return true;

            if (IsSubsetOfAnyContentType(requestAccept))
                return true;

            return false;
        }

        private MediaTypeCollection GetContentTypes(string firstArg, string[] args)
        {
            var completeArgs = new List<string>();
            completeArgs.Add(firstArg);
            completeArgs.AddRange(args);

            var contentTypes = new MediaTypeCollection();
            foreach (var arg in completeArgs)
            {
                contentTypes.Add(arg);
            }

            return contentTypes;
        }
    }

你可以用这个属性修饰任何动作.

You can decorate any action with this attribute.

请注意，它很容易更改并允许指定要检查的标题和值.

Note that it is easy to change and allow to specify the header you want to check and the value.

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