關于緩存的設計
1、什么情況下用緩存

緩存是提高應用程序性能的最好方法之一。運用緩存可以優化數據查詢，避免不必要的網絡數據回傳，和避免執行不必要的完全相同的數據處理邏輯。在實現緩存的時候我們要確定什么時候裝入緩存數據。用異步裝入緩存或用批處理方式來避免出現客戶端數據延遲。
一般來說在一定時間內請求了相同的業務邏輯而沒有變更的話，可以采用緩存來設計。數據請求頻繁的的請求不適合采用緩存，如論壇的回復，但是論壇的主題是可以采用緩存設計的。
2、緩存設計的步驟確定緩存數據結構：即設計中哪些數據用到了緩存，設計這些數據的緩存結構
確定緩存什么數據
確定緩存過期規則和清理
確定如何裝入緩存數據
3、示例 Community Server的緩存類

??1using?System;??2using?System.Collections;??3using?System.Text.RegularExpressions;??4using?System.Web;??5using?System.Web.Caching;??6??7namespace?Larry.Cache??8{??9????///?<summary>?10????///?緩存類?Community?Server的緩存類?11????///?</summary>?12????public?class?BaseCache?13????{?14????????///?<summary>?15????????///?CacheDependency?說明?16????????///?如果您向?Cache?中添加某個具有依賴項的項，當依賴項更改時，?17????????///?該項將自動從?Cache?中刪除。例如，假設您向?Cache?中添加某項，?18????????///?并使其依賴于文件名數組。當該數組中的某個文件更改時，?19????????///?與該數組關聯的項將從緩存中刪除。?20????????///?[C#]??21????????///?Insert?the?cache?item.?22????????///?CacheDependency?dep?=?new?CacheDependency(fileName,?dt);?23????????///?cache.Insert("key",?"value",?dep);?24????????///?</summary>?25????????public?static?readonly?int?DayFactor?=?17280;?26????????public?static?readonly?int?HourFactor?=?720;?27????????public?static?readonly?int?MinuteFactor?=?12;?28????????public?static?readonly?double?SecondFactor?=?0.2;?29?30????????private?static?readonly?System.Web.Caching.Cache?_cache;?31?32????????private?static?int?Factor?=?1440;?33?34????????///?<summary>?35????????///?單件模式?36????????///?</summary>?37????????static?BaseCache()?38????????{?39????????????HttpContext?context?=?HttpContext.Current;?40????????????if?(context?!=?null)?41????????????{?42????????????????_cache?=?context.Cache;?43????????????}?44????????????else?45????????????{?46????????????????_cache?=?HttpRuntime.Cache;?47????????????}?48????????}?49?50????????///?<summary>?51????????///?一次性清除所有緩存?52????????///?</summary>?53????????public?static?void?Clear()?54????????{?55????????????IDictionaryEnumerator?CacheEnum?=?_cache.GetEnumerator();?56????????????ArrayList?al?=?new?ArrayList();?57????????????while?(CacheEnum.MoveNext())?//逐個清除?58????????????{?59????????????????al.Add(CacheEnum.Key);?60????????????}?61?62????????????foreach?(string?key?in?al)?63????????????{?64????????????????_cache.Remove(key);?65????????????}?66?67????????}?68?69?70?71????????public?static?void?RemoveByPattern(string?pattern)?72????????{?73????????????IDictionaryEnumerator?CacheEnum?=?_cache.GetEnumerator();?74????????????Regex?regex?=?new?Regex(pattern,?RegexOptions.IgnoreCase?|?RegexOptions.Singleline?|?RegexOptions.Compiled);?75????????????while?(CacheEnum.MoveNext())?76????????????{?77????????????????if?(regex.IsMatch(CacheEnum.Key.ToString()))?78????????????????????_cache.Remove(CacheEnum.Key.ToString());?79????????????}?80????????}?81?82????????///?<summary>?83????????///?清除特定的緩存?84????????///?</summary>?85????????///?<param?name="key"></param>?86????????public?static?void?Remove(string?key)?87????????{?88????????????_cache.Remove(key);?89????????}?90?91????????///?<summary>?92????????///?緩存OBJECT.??93????????///?</summary>?94????????///?<param?name="key"></param>?95????????///?<param?name="obj"></param>?96????????public?static?void?Insert(string?key,?object?obj)?97????????{?98????????????Insert(key,?obj,?null,?1);?99????????}100101????????///?<summary>102????????///?緩存obj?并建立依賴項103????????///?</summary>104????????///?<param?name="key"></param>105????????///?<param?name="obj"></param>106????????///?<param?name="dep"></param>107????????public?static?void?Insert(string?key,?object?obj,?CacheDependency?dep)108????????{109????????????Insert(key,?obj,?dep,?MinuteFactor?*?3);110????????}111112????????///?<summary>113????????///?按秒緩存對象114????????///?</summary>115????????///?<param?name="key"></param>116????????///?<param?name="obj"></param>117????????///?<param?name="seconds"></param>118????????public?static?void?Insert(string?key,?object?obj,?int?seconds)119????????{120????????????Insert(key,?obj,?null,?seconds);121????????}122123????????///?<summary>124????????///?按秒緩存對象?并存儲優先級125????????///?</summary>126????????///?<param?name="key"></param>127????????///?<param?name="obj"></param>128????????///?<param?name="seconds"></param>129????????///?<param?name="priority"></param>130????????public?static?void?Insert(string?key,?object?obj,?int?seconds,?CacheItemPriority?priority)131????????{132????????????Insert(key,?obj,?null,?seconds,?priority);133????????}134135????????///?<summary>136????????///?按秒緩存對象?并建立依賴項137????????///?</summary>138????????///?<param?name="key"></param>139????????///?<param?name="obj"></param>140????????///?<param?name="dep"></param>141????????///?<param?name="seconds"></param>142????????public?static?void?Insert(string?key,?object?obj,?CacheDependency?dep,?int?seconds)143????????{144????????????Insert(key,?obj,?dep,?seconds,?CacheItemPriority.Normal);145????????}146147????????///?<summary>148????????///?按秒緩存對象?并建立具有優先級的依賴項149????????///?</summary>150????????///?<param?name="key"></param>151????????///?<param?name="obj"></param>152????????///?<param?name="dep"></param>153????????///?<param?name="seconds"></param>154????????///?<param?name="priority"></param>155????????public?static?void?Insert(string?key,?object?obj,?CacheDependency?dep,?int?seconds,?CacheItemPriority?priority)156????????{157????????????if?(obj?!=?null)158????????????{159????????????????_cache.Insert(key,?obj,?dep,?DateTime.Now.AddSeconds(Factor?*?seconds),?TimeSpan.Zero,?priority,?null);160????????????}161162????????}163164165????????public?static?void?MicroInsert(string?key,?object?obj,?int?secondFactor)166????????{167????????????if?(obj?!=?null)168????????????{169????????????????_cache.Insert(key,?obj,?null,?DateTime.Now.AddSeconds(Factor?*?secondFactor),?TimeSpan.Zero);170????????????}171????????}172173????????///?<summary>174????????///?最大時間緩存175????????///?</summary>176????????///?<param?name="key"></param>177????????///?<param?name="obj"></param>178????????public?static?void?Max(string?key,?object?obj)179????????{180????????????Max(key,?obj,?null);181????????}182183????????///?<summary>184????????///?具有依賴項的最大時間緩存185????????///?</summary>186????????///?<param?name="key"></param>187????????///?<param?name="obj"></param>188????????///?<param?name="dep"></param>189????????public?static?void?Max(string?key,?object?obj,?CacheDependency?dep)190????????{191????????????if?(obj?!=?null)192????????????{193????????????????_cache.Insert(key,?obj,?dep,?DateTime.MaxValue,?TimeSpan.Zero,?CacheItemPriority.AboveNormal,?null);194????????????}195????????}196197????????///?<summary>198????????///?Insert?an?item?into?the?cache?for?the?Maximum?allowed?time199????????///?</summary>200????????///?<param?name="key"></param>201????????///?<param?name="obj"></param>202????????public?static?void?Permanent(string?key,?object?obj)203????????{204????????????Permanent(key,?obj,?null);205????????}206207????????public?static?void?Permanent(string?key,?object?obj,?CacheDependency?dep)208????????{209????????????if?(obj?!=?null)210????????????{211????????????????_cache.Insert(key,?obj,?dep,?DateTime.MaxValue,?TimeSpan.Zero,?CacheItemPriority.NotRemovable,?null);212????????????}213????????}214215????????public?static?object?Get(string?key)216????????{217????????????return?_cache[key];218????????}219220????????///?<summary>221????????///?Return?int?of?seconds?*?SecondFactor222????????///?</summary>223????????public?static?int?SecondFactorCalculate(int?seconds)224????????{225????????????//?Insert?method?below?takes?integer?seconds,?so?we?have?to?round?any?fractional?values226????????????return?Convert.ToInt32(Math.Round((double)seconds?*?SecondFactor));227????????}228????}229}230

其實這個類就是一個單件模式的設計 和緩存的公共操作方法，其中CacheDependency表示建立緩存依賴項，CacheItemPriority表示緩存的優先級。S使用如下

1publicstaticCardShop.Model.Systems?GetConfig()?2????{?3????????const?string?cacheKey?=?"WebConfig";?4????????CardShop.Model.Systems?sampleCacheTable?=?Larry.Cache.BaseCache.Get(cacheKey)?as?CardShop.Model.Systems;?5????????if?(sampleCacheTable?==?null)?6????????{?7??????????????????????????????????OprationCheck.Message("第一次加載使用緩存");?8????????????sampleCacheTable?=?model;?9????????????Larry.Cache.BaseCache.Insert(cacheKey,?sampleCacheTable,?24?*?Larry.Cache.BaseCache.MinuteFactor);10????????}11????????else12????????{13????????????OprationCheck.Message("已經加載了緩存不需要再加載");14????????}15????????return?sampleCacheTable;16????}

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