C# 實現 key-value 結構自定義緩存 CustomCache

功能要求

使用C#編寫一個鍵值結構進程內緩存，實現數據緩存的基本操作。 這里用到的知識點如下：

-值緩存實現

說明：這里創建一個基于.net 6平臺的控制臺項目。

導入命名空間()

using?System;
using?System.Collections.Concurrent;
using?System.Collections.Generic;
using?System.Threading;
using?System.Threading.Tasks;

在.cs類中編寫實現方法

///?

///?自定義內存緩存助手
///?
public?sealed?class?CustomCacheHelper
{
????#region?單例模式
????//創建私有化靜態obj鎖??
????private?static?readonly?object?_ObjLock?=?new();
????//創建私有靜態字段，接收類的實例化對象??
????private?static?volatile?CustomCacheHelper??_Instance?=?null;
????//構造函數私有化??
????private?CustomCacheHelper()?{?}
????//創建單利對象資源并返回??
????public?static?CustomCacheHelper?GetSingleObj()
????{
????????if?(_Instance?==?null)
????????{
????????????lock?(_ObjLock)
????????????{
????????????????if?(_Instance?==?null)
????????????????{
????????????????????_Instance?=?new?CustomCacheHelper();
????????????????}
????????????}
????????}
????????return?_Instance;
????}
????#endregion

????///?

????///?緩存字典?=>?【key|value|time】
????///?
????private?static?volatile?ConcurrentDictionary<string,?KeyValuePair<object,?DateTime?>>?_CacheDictionary?=?new();

????///?

????///?1.主動過期
????///?
????static?CustomCacheHelper()
????{
????????Task.Run(()?=>?{
????????????while?(true)
????????????{
????????????????int?millisecondsTimeout?=?1000?*?60?*?10;
????????????????Thread.Sleep(millisecondsTimeout);?//10分鐘檢查一次

????????????????if?(_CacheDictionary?!=?null?&&?_CacheDictionary.Keys.Count?>?0)
????????????????{
????????????????????ICollection<string>?listKey?=?_CacheDictionary.Keys;
????????????????????foreach?(var?key?in?listKey)
????????????????????{
????????????????????????var?valueTime?=?_CacheDictionary[key];
????????????????????????if?(valueTime.Value?????????????????????????{
????????????????????????????_CacheDictionary.TryRemove(key,?out?KeyValuePair<object,?DateTime?>?value);
????????????????????????}
????????????????????}
????????????????}
????????????}
????????});
????}

????///?

????///?索引器
????///?
????///?
????///?
????public?object?this[string?key]
????{
????????get?=>?_CacheDictionary[key];
????????set?=>?_CacheDictionary[key]?=?new?KeyValuePair<object,?DateTime?>(value,?null);
????}

????///?

????///?設置相對過期緩存
????///?
????///?鍵
????///?數據包
????///?相對過期時間
????public?void?Set(string?key,?object?data,?int?seconds)
????{
????????var?expirationTime?=?DateTime.Now.AddSeconds(seconds);
????????_CacheDictionary[key]?=?new?KeyValuePair<object,?DateTime?>(data,?expirationTime);
????}

????///?

????///?設置絕對過期緩存
????///?
????///?鍵<
????///?數據包
????public?void?Set(string?key,?object?data)
????{
????????this[key]?=?data;?//?下面代碼等效
????????//?_CacheDictionary[key]?=?new?KeyValuePair(data,?null);
????}

????///?

????///?通過key獲取緩存value
????///?2.被動過期
????///?
????///?
????///?
????///?
????public?T??Get(string?key)
????{
????????if?(Exist(key))
????????{
????????????//var?valueTime?=?_CacheDictionary[key];
????????????//return?(T)valueTime.Key;?//return?(T)this[key];

????????????bool?hasValue?=?_CacheDictionary.TryGetValue(key,?out?KeyValuePair<object,?DateTime?>?value);
????????????if?(hasValue)
????????????{
????????????????return?(T)value.Key;?//return?(T)this[key];
????????????}
????????}

????????return?default;
????}

????///?

????///?獲取所有的key
????///?
????///?
????public?ICollection<string>?GetKeys()?=>?_CacheDictionary.Keys;

????///?

????///?獲取緩存個數
????///?
????///?
????public?int?Count()
????{
????????int?count?=?0;
????????if?(_CacheDictionary?!=?null)
????????{
????????????count?=?_CacheDictionary.Count;
????????}
????????return?count;
????}

????///?

????///?刪除指定key的value
????///?
????///?
????public?void?Remove(string?key)
????{
????????if?(Exist(key))
????????{
????????????_CacheDictionary.TryRemove(key,?out?KeyValuePair<object,?DateTime?>?value);
????????}
????}

????///?

????///?清空所有緩存
????///?
????public?void?Cleaner()
????{
????????if?(_CacheDictionary?!=?null?&&?_CacheDictionary.Count?>?0)
????????{
????????????foreach?(var?key?in?_CacheDictionary.Keys)
????????????{
????????????????_CacheDictionary.TryRemove(key,?out?KeyValuePair<object,?DateTime?>?value);
????????????}
????????}
????}

????///?

????///?2.被動過期，保證任何過期緩存都無法取值
????///?檢查key是否存在
????///?
????///?
????///?
????public?bool?Exist(string?key)
????{
????????bool?isExist?=?false;
????????if?(!string.IsNullOrWhiteSpace(key)?&&?_CacheDictionary.ContainsKey(key))
????????{
????????????var?valTime?=?_CacheDictionary[key];

????????????if?(valTime.Value?!=?null?&&?valTime.Value?>?DateTime.Now)
????????????{
????????????????isExist?=?true;?//緩存沒過期
????????????}
????????????else
????????????{
????????????????if?(valTime.Value?==?null)
????????????????{
????????????????????isExist?=?true;?//永久緩存
????????????????}
????????????????else
????????????????{
????????????????????_CacheDictionary.TryRemove(key,?out?KeyValuePair<object,?DateTime?>?value);?//緩存過期清理
????????????????}
????????????}
????????}
????????return?isExist;
????}
}

Main方法使用緩存

由于項目是用控制臺程序編寫的，所以我們可以直接在Main方法中添加如下代碼：

var?customCache?=?CustomCacheHelper.GetSingleObj();
customCache.Set("key1",?"value1");
customCache.Set("key2",?"value2",?3);
customCache.Set("key3",?"value3",?6);
var?keys?=?customCache.GetKeys();

Console.WriteLine("首次打印：");
foreach?(var?key?in?keys)
{
????Console.WriteLine($"time:{DateTime.Now},key={key},value={customCache.Get<string>(key)}");
}

Console.WriteLine("睡眠5s后再次打?。?);
Thread.Sleep(5000);
foreach?(var?key?in?keys)
{
????Console.WriteLine($"time:{DateTime.Now},key={key},value={customCache.Get<string>(key)}");
}

這里的代碼中，我們添加了三組鍵值數據，其中一組不設置過期時間，另外兩組設置過期時間。 保存數據后，分別打印緩存中保存的數據，在第二次緩存打印之前，先讓線程休眠等待5秒（5000毫秒），并注意控制臺輸出的信息。

開始測試

從控制臺輸出的信息可以看到key=key2的值為空，這說明我們內部調用Exist方法已經生效，key2的值緩存的有效時間為3秒。 當第二次打印出信息時，此時已經休眠了5秒，key2中存儲的內存數據已經超時，而key3中存儲的值有效期為6秒，沒有超時，這樣就可以一一獲取對應的內存數據。

開始測試

通過上面的demo演示，我們實現了一個自定義的進程內緩存助手，可以很方便的導入到項目中使用。

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