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// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
using System;
using System.Collections.Generic;
using System.Linq;
using Microsoft.AspNetCore.Mvc.Abstractions;
using Microsoft.AspNetCore.Mvc.ActionConstraints;
using Microsoft.AspNetCore.Mvc.ApiExplorer;
using Microsoft.AspNetCore.Mvc.Core;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.AspNetCore.Mvc.Formatters;
using Microsoft.AspNetCore.Mvc.Internal;
using Microsoft.Net.Http.Headers;
namespace Microsoft.AspNetCore.Mvc
{
/// <summary>
/// A filter that specifies the supported request content types. <see cref="ContentTypes"/> is used to select an
/// action when there would otherwise be multiple matches.
/// </summary>
[AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
public class ConsumesAttribute :
Attribute,
IResourceFilter,
IConsumesActionConstraint,
IApiRequestMetadataProvider
{
public static readonly int ConsumesActionConstraintOrder = 200;
/// <summary>
/// Creates a new instance of <see cref="ConsumesAttribute"/>.
/// </summary>
public ConsumesAttribute(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);
}
// The value used is a non default value so that it avoids getting mixed with other action constraints
// with default order.
/// <inheritdoc />
int IActionConstraint.Order { get; } = ConsumesActionConstraintOrder;
/// <summary>
/// Gets or sets the supported request content types. Used to select an action when there would otherwise be
/// multiple matches.
/// </summary>
public MediaTypeCollection ContentTypes { get; set; }
/// <inheritdoc />
public void OnResourceExecuting(ResourceExecutingContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
// Only execute if the current filter is the one which is closest to the action.
// Ignore all other filters. This is to ensure we have a overriding behavior.
if (IsApplicable(context.ActionDescriptor))
{
var requestContentType = context.HttpContext.Request.ContentType;
// Confirm the request's content type is more specific than a media type this action supports e.g. OK
// if client sent "text/plain" data and this action supports "text/*".
if (requestContentType != null && !IsSubsetOfAnyContentType(requestContentType))
{
context.Result = new UnsupportedMediaTypeResult();
}
}
}
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;
}
/// <inheritdoc />
public void OnResourceExecuted(ResourceExecutedContext context)
{
if (context == null)
{
throw new ArgumentNullException(nameof(context));
}
}
/// <inheritdoc />
public bool Accept(ActionConstraintContext context)
{
// If this constraint is not closest to the action, it will be skipped.
if (!IsApplicable(context.CurrentCandidate.Action))
{
// Since the constraint is to be skipped, returning true here
// will let the current candidate ignore this constraint and will
// be selected based on other constraints for this action.
return true;
}
var requestContentType = context.RouteContext.HttpContext.Request.ContentType;
// If the request content type is null we need to act like pass through.
// In case there is a single candidate with a constraint it should be selected.
// If there are multiple actions with consumes action constraints this should result in ambiguous exception
// unless there is another action without a consumes constraint.
if (requestContentType == null)
{
var isActionWithoutConsumeConstraintPresent = context.Candidates.Any(
candidate => candidate.Constraints == null ||
!candidate.Constraints.Any(constraint => constraint is IConsumesActionConstraint));
return !isActionWithoutConsumeConstraintPresent;
}
// Confirm the request's content type is more specific than (a media type this action supports e.g. OK
// if client sent "text/plain" data and this action supports "text/*".
if (IsSubsetOfAnyContentType(requestContentType))
{
return true;
}
var firstCandidate = context.Candidates[0];
if (firstCandidate.Action != context.CurrentCandidate.Action)
{
// If the current candidate is not same as the first candidate,
// we need not probe other candidates to see if they apply.
// Only the first candidate is allowed to probe other candidates and based on the result select itself.
return false;
}
// Run the matching logic for all IConsumesActionConstraints we can find, and see what matches.
// 1). If we have a unique best match, then only that constraint should return true.
// 2). If we have multiple matches, then all constraints that match will return true
// , resulting in ambiguity(maybe).
// 3). If we have no matches, then we choose the first constraint to return true.It will later return a 415
foreach (var candidate in context.Candidates)
{
if (candidate.Action == firstCandidate.Action)
{
continue;
}
var tempContext = new ActionConstraintContext()
{
Candidates = context.Candidates,
RouteContext = context.RouteContext,
CurrentCandidate = candidate
};
if (candidate.Constraints == null || candidate.Constraints.Count == 0 ||
candidate.Constraints.Any(constraint => constraint is IConsumesActionConstraint &&
constraint.Accept(tempContext)))
{
// There is someone later in the chain which can handle the request.
// end the process here.
return false;
}
}
// There is no one later in the chain that can handle this content type return a false positive so that
// later we can detect and return a 415.
return true;
}
private bool IsApplicable(ActionDescriptor actionDescriptor)
{
// If there are multiple IConsumeActionConstraints which are defined at the class and
// at the action level, the one closest to the action overrides the others. To ensure this
// we take advantage of the fact that ConsumesAttribute is both an IActionFilter and an
// IConsumeActionConstraint. Since filterdescriptor collection is ordered (the last filter is the one
// closest to the action), we apply this constraint only if there is no IConsumeActionConstraint after this.
return actionDescriptor.FilterDescriptors.Last(
filter => filter.Filter is IConsumesActionConstraint).Filter == this;
}
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)
{
var mediaType = new MediaType(arg);
if (mediaType.MatchesAllSubTypes ||
mediaType.MatchesAllTypes)
{
throw new InvalidOperationException(
Resources.FormatMatchAllContentTypeIsNotAllowed(arg));
}
contentTypes.Add(arg);
}
return contentTypes;
}
/// <inheritdoc />
public void SetContentTypes(MediaTypeCollection contentTypes)
{
contentTypes.Clear();
foreach (var contentType in ContentTypes)
{
contentTypes.Add(contentType);
}
}
}
}