CacheHelper对缓存的控制

通常我们针对页面以及相关数据进行相应的缓存（分为客户端和服务端的缓存），以下代码为对一般操作进行相应的缓存（服务端），用以减少对数据库的访问次数，减少服务器的压力。

 

（一）CacheHelper类

CacheHelper类主要是依赖于系统的System.Web.Caching.HostingEnvironment.Cache，具体代码如下:

    public static class CacheHelper
    {
        private static Cache _cache;

        public static double SaveTime 
        { 
            get; 
            set;
        }

        static CacheHelper()
        {
            _cache = HostingEnvironment.Cache;
            SaveTime = 15.0;
        }

        public static object Get(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                return null;
            }

            return _cache.Get(key);
        }

        public static T Get<T>(string key)
        {
            object obj = Get(key);
            return obj==null?default(T):(T)obj;
        }

        public static void Insert(string key, object value, CacheDependency dependency, CacheItemPriority priority, CacheItemRemovedCallback callback)
        {
            _cache.Insert(key, value, dependency, Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(SaveTime), priority, callback);
        }

        public static void Insert(string key, object value, CacheDependency dependency, CacheItemRemovedCallback callback)
        {
            Insert(key, value, dependency, CacheItemPriority.Default, callback);
        }

        public static void Insert(string key, object value, CacheDependency dependency)
        {
            Insert(key, value, dependency, CacheItemPriority.Default, null);
        }

        public static void Insert(string key, object value)
        {
            Insert(key, value, null, CacheItemPriority.Default, null);
        }

        public static void Remove(string key)
        {
            if (string.IsNullOrEmpty(key))
            {
                return;
            }

            _cache.Remove(key);
        }

        public static IList<string> GetKeys()
        {
            List<string> keys = new List<string>();
            IDictionaryEnumerator enumerator = _cache.GetEnumerator();
            while (enumerator.MoveNext())
            {
                keys.Add(enumerator.Key.ToString());
            }

            return keys.AsReadOnly();
        }

        public static void RemoveAll()
        {
            IList<string> keys = GetKeys();
            foreach (string key in keys)
            {
                _cache.Remove(key);
            }
        }
    }
}

在原有基础上增加了如下3个方法：

（1）public static T Get<T>(string key)

（2）public static IList<string> GetKeys()

（3）public static void RemoveAll()

这样我们能够方便的以静态方法来对Cache进行相应的操作。

 

（二）Cache类

Cache类位于System.Web.Caching命名空间下，实现了IEnumerable接口，主要方法如下：

    public sealed class Cache : IEnumerable
    {
         public object Get(string key);
         public IDictionaryEnumerator GetEnumerator();
         public void Insert(string key, object value);
         public void Insert(string key, object value, CacheDependency dependencies);
         public void Insert(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration);
         public void Insert(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemUpdateCallback onUpdateCallback);
         public void Insert(string key, object value, CacheDependency dependencies, DateTime absoluteExpiration, TimeSpan slidingExpiration, CacheItemPriority priority, CacheItemRemovedCallback onRemoveCallback);
        
         public object Remove(string key);
    }

在底层，应该是以一个字典来对相关的键值对来进行数据保存。

（三）CacheHelper相关的单元测试

    [TestClass()]
    public class CacheHelperTest
    {
        /// <summary>
        ///Get 的测试
        ///</summary>
        [TestMethod()]
        public void GetTest()
        {
            string key = "key"; 
            object actual = CacheHelper.Get(key);
            Assert.IsNull(actual);

            Cache cache = HostingEnvironment.Cache;
            string value="value";
            cache.Insert(key,value);
            actual = CacheHelper.Get(key);

            Assert.IsNotNull(actual);
            Assert.IsTrue(actual.ToString()==value);
        }

        /// <summary>
        ///Get 的测试
        ///</summary>
        [TestMethod()]
        public void GetWithAbnormalParameterTest() 
        {
            object actual = CacheHelper.Get(string.Empty);
            Assert.IsNull(actual);

            actual = CacheHelper.Get(null);
            Assert.IsNull(actual);
        } 

        /// <summary>
        ///GetKeys 的测试
        ///</summary>
        [TestMethod()]
        public void GetKeysTest()
        {
            int count = (new Random()).Next(10);
            IList<string> keys = CreateAllKeys(count);
            InsertAllKeys(keys);
            IList<string> results = CacheHelper.GetKeys();
            Assert.IsTrue(results.Count == count);

            for (int index = 0; index < count; index++)
            { 
               Assert.IsTrue(results.Contains(keys[index]));
            }

            for (int index = 0; index < count; index++)
            {
                Assert.IsTrue(keys.Contains(results[index]));
            }
        }

        private void InsertAllKeys(IList<string> keys)
        {
            Cache cache = HostingEnvironment.Cache;
            foreach (string key in keys)
            {
                cache.Insert(key,key);
            }
        }

        private IList<string> CreateAllKeys(int count)
        {
            IList<string> keys = new List<string>();
            for (int index = 0; index < count; index++)
            {
                keys.Add("KEY"+index.ToString());
            }

            return keys;
        }

        /// <summary>
        ///Remove 的测试
        ///</summary>
        [TestMethod()]
        public void RemoveTest()
        {
            int count = 1;
            IList<string> keys = CreateAllKeys(count);
            InsertAllKeys(keys);
            string key = keys[0];

            IList<string> results = CacheHelper.GetKeys();
            Assert.IsTrue(results.Contains(key));

            CacheHelper.Remove(key);

            results = CacheHelper.GetKeys();
            Assert.IsFalse(results.Contains(key));
        }

        /// <summary>
        ///RemoveAll 的测试
        ///</summary>
        [TestMethod()]
        public void RemoveAllTest()
        {
            int count = (new Random()).Next(20);
            IList<string> keys = CreateAllKeys(count);
            InsertAllKeys(keys);
           
            IList<string> results = CacheHelper.GetKeys();
            foreach (string key in keys)
            {
                Assert.IsTrue(results.Contains(key));
            }
    
            CacheHelper.RemoveAll();

            results = CacheHelper.GetKeys();
            Assert.IsTrue(results.Count==0);
        }

        /// <summary>
        ///SaveTime 的测试
        ///</summary>
        [TestMethod()]
        public void SaveTimeTest()
        {
            double expected = (new Random()).Next(10000);
            double actual;
            CacheHelper.SaveTime = expected;
            actual = CacheHelper.SaveTime;
            Assert.IsTrue(expected==actual);
        }
    }

 

这个上面的仅仅是对一些基本的方法进行了单元测试，基本验证了方法的逻辑，当然不包括那些重载方法的验证。至于为什么写这样相关的类，主要是能够以静态的方法来对Cache进行统一的操作，仅仅是为了方便与统一。

 

源代码下载：缓存类与单元测试源代码下载