为了提高一个系统或网站的性能和IO吞吐量，我们一般都会采用缓存技术。当然NopCommerce也不例外，本文我们就来给大家分析一下nop中Cache缓存相关类设计、核心源码及实现原理。
一、Nop.Core.Caching.ICacheManager
Nop首先抽象出了一个缓存存储和读取相关管理接口Nop.Core.Caching.ICacheManager。
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namespace Nop.Core.Caching { /// <summary> /// Cache manager interface /// </summary> public interface ICacheManager { /// <summary> /// Gets or sets the value associated with the specified key. /// </summary> /// <typeparam name="T">Type</typeparam> /// <param name="key">The key of the value to get.</param> /// <returns>The value associated with the specified key.</returns> T Get<T>(string key); /// <summary> /// Adds the specified key and object to the cache. /// </summary> /// <param name="key">key</param> /// <param name="data">Data</param> /// <param name="cacheTime">Cache time</param> void Set(string key, object data, int cacheTime); /// <summary> /// Gets a value indicating whether the value associated with the specified key is cached /// </summary> /// <param name="key">key</param> /// <returns>Result</returns> bool IsSet(string key); /// <summary> /// Removes the value with the specified key from the cache /// </summary> /// <param name="key">/key</param> void Remove(string key); /// <summary> /// Removes items by pattern /// </summary> /// <param name="pattern">pattern</param> void RemoveByPattern(string pattern); /// <summary> /// Clear all cache data /// </summary> void Clear(); } } 二、Nop.Core.Caching.MemoryCacheManager 接口ICacheManager具体实现是在类Nop.Core.Caching.MemoryCacheManager： using System; using System.Collections.Generic; using System.Runtime.Caching; using System.Text.RegularExpressions; namespace Nop.Core.Caching { /// <summary> /// Represents a manager for caching between HTTP requests (long term caching) /// </summary> public partial class MemoryCacheManager : ICacheManager { protected ObjectCache Cache { get { return MemoryCache.Default; } } /// <summary> /// Gets or sets the value associated with the specified key. /// </summary> /// <typeparam name="T">Type</typeparam> /// <param name="key">The key of the value to get.</param> /// <returns>The value associated with the specified key.</returns> public virtual T Get<T>(string key) { return (T)Cache[key]; } /// <summary> /// Adds the specified key and object to the cache. /// </summary> /// <param name="key">key</param> /// <param name="data">Data</param> /// <param name="cacheTime">Cache time</param> public virtual void Set(string key, object data, int cacheTime) { if (data == null) return; var policy = new CacheItemPolicy(); policy.AbsoluteExpiration = DateTime.Now + TimeSpan.FromMinutes(cacheTime); Cache.Add(new CacheItem(key, data), policy); } /// <summary> /// Gets a value indicating whether the value associated with the specified key is cached /// </summary> /// <param name="key">key</param> /// <returns>Result</returns> public virtual bool IsSet(string key) { return (Cache.Contains(key)); } /// <summary> /// Removes the value with the specified key from the cache /// </summary> /// <param name="key">/key</param> public virtual void Remove(string key) { Cache.Remove(key); } /// <summary> /// Removes items by pattern /// </summary> /// <param name="pattern">pattern</param> public virtual void RemoveByPattern(string pattern) { var regex = new Regex(pattern, RegexOptions.Singleline | RegexOptions.Compiled | RegexOptions.IgnoreCase); var keysToRemove = new List<String>(); foreach (var item in Cache) if (regex.IsMatch(item.Key)) keysToRemove.Add(item.Key); foreach (string key in keysToRemove) { Remove(key); } } /// <summary> /// Clear all cache data /// </summary> public virtual void Clear() { foreach (var item in Cache) Remove(item.Key); } } }
可以看到上面Nop的缓存数据是使用的的MemoryCache.Default来存储的，MemoryCache.Default是获取对默认 System.Runtime.Caching.MemoryCache 实例的引用，缓存的默认实例，也就是程序运行的内存中。
Nop除了提供了一个MemoryCacheManager，还有一个Nop.Core.Caching.PerRequestCacheManager类，它提供的是MemoryCacheManager相同的功能，不过它是把数据存在HttpContextBase.Items中，如下：
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using System; using System.Collections; using System.Collections.Generic; using System.Text.RegularExpressions; using System.Web; namespace Nop.Core.Caching { /// <summary> /// Represents a manager for caching during an HTTP request (short term caching) /// </summary> public partial class PerRequestCacheManager : ICacheManager { private readonly HttpContextBase _context; /// <summary> /// Ctor /// </summary> /// <param name="context">Context</param> public PerRequestCacheManager(HttpContextBase context) { this._context = context; } /// <summary> /// Creates a new instance of the NopRequestCache class /// </summary> protected virtual IDictionary GetItems() { if (_context != null) return _context.Items; return null; } //省略其它代码.... } }
三、缓存接口ICacheManager依赖注入
缓存接口ICacheManager使用了依赖注入，我们在Nop.Web.Framework.DependencyRegistrar类中就能找到对ICacheManager的注册代码：
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//cache manager builder.RegisterType<MemoryCacheManager>().As<ICacheManager>().Named<ICacheManager>("nop_cache_static").SingleInstance(); builder.RegisterType<PerRequestCacheManager>().As<ICacheManager>().Named<ICacheManager>("nop_cache_per_request").InstancePerLifetimeScope(); //pass MemoryCacheManager as cacheManager (cache settings between requests) builder.RegisterType<ProductTagService>().As<IProductTagService>() .WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static")) .InstancePerLifetimeScope(); //pass MemoryCacheManager as cacheManager (cache settings between requests) builder.RegisterType<PermissionService>().As<IPermissionService>() .WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static")) .InstancePerLifetimeScope(); //pass MemoryCacheManager as cacheManager (cache settings between requests) builder.RegisterType<AclService>().As<IAclService>() .WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static")) .InstancePerLifetimeScope(); //pass MemoryCacheManager as cacheManager (cache settings between requests) builder.RegisterType<PriceCalculationService>().As<IPriceCalculationService>() .WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static")) .InstancePerLifetimeScope(); //pass MemoryCacheManager as cacheManager (cache settings between requests) builder.RegisterType<CustomerActivityService>().As<ICustomerActivityService>() .WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static")) .InstancePerLifetimeScope();
上面最开始对接口ICacheManager两实现分别是MemoryCacheManager和PerRequestCacheManager并通过.Named来区分。Autofac高级特性--注册Named命名和Key Service服务
接下来可以配置不同的Service依赖不同的ICacheManager的实现：.WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_static"))或者.WithParameter(ResolvedParameter.ForNamed<ICacheManager>("nop_cache_per_request"))。
四、具体实例BlogController
下面我们来举例看一下怎么使用这个缓存的。我们就以Nop.Web.Controllers.BlogController的方法BlogTags为例：
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[ChildActionOnly] public ActionResult BlogTags() { if (!_blogSettings.Enabled) return Content(""); var cacheKey = string.Format(ModelCacheEventConsumer.BLOG_TAGS_MODEL_KEY, _workContext.WorkingLanguage.Id, _storeContext.CurrentStore.Id); var cachedModel = _cacheManager.Get(cacheKey, () => { var model = new BlogPostTagListModel(); //get tags var tags = _blogService.GetAllBlogPostTags(_storeContext.CurrentStore.Id, _workContext.WorkingLanguage.Id) .OrderByDescending(x => x.BlogPostCount) .Take(_blogSettings.NumberOfTags) .ToList(); //sorting tags = tags.OrderBy(x => x.Name).ToList(); foreach (var tag in tags) model.Tags.Add(new BlogPostTagModel() { Name = tag.Name, BlogPostCount = tag.BlogPostCount }); return model; }); return PartialView(cachedModel); }
上面var cachedModel = _cacheManager.Get就是从缓存中读取数据，_cacheManager的Get方法第二个参数是一个lambda表达式，可以传一个方法，这时我们就可以把数据的从数据库中的逻辑放在里面，注意：当第二次请求数据时，如果缓存中有数据，这个Lambda方法是不会执行的。为什么呢？我们可以选中_cacheManager的Get方法按F12进去看这个方法的实现就知道了：
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using System; namespace Nop.Core.Caching { /// <summary> /// Extensions /// </summary> public static class CacheExtensions { /// <summary> /// Get a cached item. If it's not in the cache yet, then load and cache it /// </summary> /// <typeparam name="T">Type</typeparam> /// <param name="cacheManager">Cache manager</param> /// <param name="key">Cache key</param> /// <param name="acquire">Function to load item if it's not in the cache yet</param> /// <returns>Cached item</returns> public static T Get<T>(this ICacheManager cacheManager, string key, Func<T> acquire) { return Get(cacheManager, key, 60, acquire); } /// <summary> /// Get a cached item. If it's not in the cache yet, then load and cache it /// </summary> /// <typeparam name="T">Type</typeparam> /// <param name="cacheManager">Cache manager</param> /// <param name="key">Cache key</param> /// <param name="cacheTime">Cache time in minutes (0 - do not cache)</param> /// <param name="acquire">Function to load item if it's not in the cache yet</param> /// <returns>Cached item</returns> public static T Get<T>(this ICacheManager cacheManager, string key, int cacheTime, Func<T> acquire) { if (cacheManager.IsSet(key)) { return cacheManager.Get<T>(key); } else { var result = acquire(); if (cacheTime > 0) cacheManager.Set(key, result, cacheTime); return result; } } } }
可以看到其实上面_cacheManager.Get调用的是类型ICacheManager的一个扩展方法。第二个方法就可以知道，当缓存中有数据直接返回cacheManager.Get<T>(key)，如果没有才进入else分支，执行参数的Lambda表达方式acquire()。
博客园的这篇文章写的不错：http://www.cnblogs.com/gusixing/archive/2012/04/12/2443799.html