aspnetcore/src/Microsoft.AspNetCore.Mvc.Core/ResponseCacheAttribute.cs

// 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 Microsoft.AspNetCore.Mvc.Core;
using Microsoft.AspNetCore.Mvc.Filters;
using Microsoft.AspNetCore.Mvc.Internal;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Options;

namespace Microsoft.AspNetCore.Mvc
{
    /// <summary>
    /// Specifies the parameters necessary for setting appropriate headers in response caching.
    /// </summary>
    [AttributeUsage(AttributeTargets.Class | AttributeTargets.Method, AllowMultiple = false, Inherited = true)]
    public class ResponseCacheAttribute : Attribute, IFilterFactory, IOrderedFilter
    {
        // A nullable-int cannot be used as an Attribute parameter.
        // Hence this nullable-int is present to back the Duration property.
        // The same goes for nullable-ResponseCacheLocation and nullable-bool.
        private int? _duration;
        private ResponseCacheLocation? _location;
        private bool? _noStore;

        /// <summary>
        /// Gets or sets the duration in seconds for which the response is cached.
        /// This sets "max-age" in "Cache-control" header.
        /// </summary>
        public int Duration
        {
            get
            {
                return _duration ?? 0;
            }
            set
            {
                _duration = value;
            }
        }

        /// <summary>
        /// Gets or sets the location where the data from a particular URL must be cached.
        /// </summary>
        public ResponseCacheLocation Location
        {
            get
            {
                return _location ?? ResponseCacheLocation.Any;
            }
            set
            {
                _location = value;
            }
        }

        /// <summary>
        /// Gets or sets the value which determines whether the data should be stored or not.
        /// When set to <see langword="true"/>, it sets "Cache-control" header to "no-store".
        /// Ignores the "Location" parameter for values other than "None".
        /// Ignores the "duration" parameter.
        /// </summary>
        public bool NoStore
        {
            get
            {
                return _noStore ?? false;
            }
            set
            {
                _noStore = value;
            }
        }

        /// <summary>
        /// Gets or sets the value for the Vary response header.
        /// </summary>
        public string VaryByHeader { get; set; }

        /// <summary>
        /// Gets or sets the value of the cache profile name.
        /// </summary>
        public string CacheProfileName { get; set; }

        /// <inheritdoc />
        public int Order { get; set; }

        /// <inheritdoc />
        public bool IsReusable => true;

        /// <inheritdoc />
        public IFilterMetadata CreateInstance(IServiceProvider serviceProvider)
        {
            if (serviceProvider == null)
            {
                throw new ArgumentNullException(nameof(serviceProvider));
            }

            var optionsAccessor = serviceProvider.GetRequiredService<IOptions<MvcOptions>>();

            CacheProfile selectedProfile = null;
            if (CacheProfileName != null)
            {
                optionsAccessor.Value.CacheProfiles.TryGetValue(CacheProfileName, out selectedProfile);
                if (selectedProfile == null)
                {
                    throw new InvalidOperationException(Resources.FormatCacheProfileNotFound(CacheProfileName));
                }
            }

            // If the ResponseCacheAttribute parameters are set,
            // then it must override the values from the Cache Profile.
            // The below expression first checks if the duration is set by the attribute's parameter.
            // If absent, it checks the selected cache profile (Note: There can be no cache profile as well)
            // The same is the case for other properties.
            _duration = _duration ?? selectedProfile?.Duration;
            _noStore = _noStore ?? selectedProfile?.NoStore;
            _location = _location ?? selectedProfile?.Location;
            VaryByHeader = VaryByHeader ?? selectedProfile?.VaryByHeader;

            // ResponseCacheFilter cannot take any null values. Hence, if there are any null values,
            // the properties convert them to their defaults and are passed on.
            return new ResponseCacheFilter(new CacheProfile
            {
                Duration = _duration,
                Location = _location,
                NoStore = _noStore,
                VaryByHeader = VaryByHeader
            });
        }
    }
}