nopCommerce 数据缓存

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。

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：

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：

//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：

[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：

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