ASP.NET Core 選項模式源碼學習Options IOptions（二）

前言

上一篇文章介紹IOptions的註冊,本章我們繼續往下看

IOptions

IOptions是一個介面裡面只有一個Values屬性，該介面通過OptionsManager實現

   public interface IOptions<out TOptions> where TOptions : class, new()
    {
        /// <summary>
        /// The default configured <typeparamref name="TOptions"/> instance
        /// </summary>
        TOptions Value { get; }
    }

OptionsManager

OptionsManager實現了IOptions<>和IOptionsSnapshot<>，他使用內部屬性OptionsCache 進行緩存操作；實現IOptionsSnapshot介面Get(string name)其實就是獲取我們第一章所指定的Name，通過IOptionsFactory<>創建TOptions實例

    public class OptionsManager<TOptions> : IOptions<TOptions>, IOptionsSnapshot<TOptions> where TOptions : class, new()
    {
        private readonly IOptionsFactory<TOptions> _factory;
        private readonly OptionsCache<TOptions> _cache = new OptionsCache<TOptions>(); // Note: this is a private cache

        /// <summary>
        /// Initializes a new instance with the specified options configurations.
        /// </summary>
        /// <param name="factory">The factory to use to create options.</param>
        public OptionsManager(IOptionsFactory<TOptions> factory)
        {
            _factory = factory;
        }

        /// <summary>
        /// The default configured <typeparamref name="TOptions"/> instance, equivalent to Get(Options.DefaultName).
        /// </summary>
        public TOptions Value
        {
            get
            {
                return Get(Options.DefaultName);
            }
        }

        /// <summary>
        /// Returns a configured <typeparamref name="TOptions"/> instance with the given <paramref name="name"/>.
        /// </summary>
        public virtual TOptions Get(string name)
        {
            name = name ?? Options.DefaultName;

            // Store the options in our instance cache
            return _cache.GetOrAdd(name, () => _factory.Create(name));
        }
    }
    
        public interface IOptionsSnapshot<out TOptions> : IOptions<TOptions> where TOptions : class, new()
    {
        /// <summary>
        /// Returns a configured <typeparamref name="TOptions"/> instance with the given name.
        /// </summary>
        TOptions Get(string name);
    }

OptionsCache

OptionsCache採用了線程安全字典ConcurrentDictionary進行了封裝用於記憶體緩存

    public class OptionsCache<TOptions> : IOptionsMonitorCache<TOptions> where TOptions : class
    {
        private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(StringComparer.Ordinal);

        /// <summary>
        /// Clears all options instances from the cache.
        /// </summary>
        public void Clear() => _cache.Clear();

        /// <summary>
        /// Gets a named options instance, or adds a new instance created with <paramref name="createOptions"/>.
        /// </summary>
        /// <param name="name">The name of the options instance.</param>
        /// <param name="createOptions">The func used to create the new instance.</param>
        /// <returns>The options instance.</returns>
        public virtual TOptions GetOrAdd(string name, Func<TOptions> createOptions)
        {
            if (createOptions == null)
            {
                throw new ArgumentNullException(nameof(createOptions));
            }
            name = name ?? Options.DefaultName;
            return _cache.GetOrAdd(name, new Lazy<TOptions>(createOptions)).Value;
        }

        /// <summary>
        /// Tries to adds a new option to the cache, will return false if the name already exists.
        /// </summary>
        /// <param name="name">The name of the options instance.</param>
        /// <param name="options">The options instance.</param>
        /// <returns>Whether anything was added.</returns>
        public virtual bool TryAdd(string name, TOptions options)
        {
            if (options == null)
            {
                throw new ArgumentNullException(nameof(options));
            }
            name = name ?? Options.DefaultName;
            return _cache.TryAdd(name, new Lazy<TOptions>(() => options));
        }

        /// <summary>
        /// Try to remove an options instance.
        /// </summary>
        /// <param name="name">The name of the options instance.</param>
        /// <returns>Whether anything was removed.</returns>
        public virtual bool TryRemove(string name)
        {
            name = name ?? Options.DefaultName;
            return _cache.TryRemove(name, out var ignored);
        }
    }

OptionsFactory

OptionsFactory實現了 IOptionsFactory.Create(string name);,
而OptionsFactory構造函數中註入了IConfigureOptions<>和IPostConfigureOptions<>，
這裡使用了IEnumerable類型標識當註冊多個時候按照次數依次的執行，從如下代碼中我們也看到了我們在上一章中所說的Configures和postConfigures註冊先後順序問題。

    public class OptionsFactory<TOptions> : IOptionsFactory<TOptions> where TOptions : class, new()
    {
        private readonly IEnumerable<IConfigureOptions<TOptions>> _setups;
        private readonly IEnumerable<IPostConfigureOptions<TOptions>> _postConfigures;
        private readonly IEnumerable<IValidateOptions<TOptions>> _validations;

        public OptionsFactory(IEnumerable<IConfigureOptions<TOptions>> setups, IEnumerable<IPostConfigureOptions<TOptions>> postConfigures) : this(setups, postConfigures, validations: null)
        { }

       
      
        public OptionsFactory(IEnumerable<IConfigureOptions<TOptions>> setups, IEnumerable<IPostConfigureOptions<TOptions>> postConfigures, IEnumerable<IValidateOptions<TOptions>> validations)
        {
            _setups = setups;
            _postConfigures = postConfigures;
            _validations = validations;
        }

       
        public TOptions Create(string name)
        {
            var options = new TOptions();
            foreach (var setup in _setups)
            {
                if (setup is IConfigureNamedOptions<TOptions> namedSetup)
                {
                    namedSetup.Configure(name, options);
                }
                else if (name == Options.DefaultName)
                {
                    setup.Configure(options);
                }
            }
            foreach (var post in _postConfigures)
            {
                post.PostConfigure(name, options);
            }

            if (_validations != null)
            {
                var failures = new List<string>();
                foreach (var validate in _validations)
                {
                    var result = validate.Validate(name, options);
                    if (result.Failed)
                    {
                        failures.AddRange(result.Failures);
                    }
                }
                if (failures.Count > 0)
                {
                    throw new OptionsValidationException(name, typeof(TOptions), failures);
                }
            }

            return options;
        }
    }