企業庫緩存依賴的實現-基于文件依賴

作者: 網絡漁夫來源: 博客園發布時間: 2009-07-14 17:33 閱讀: 2831 次推薦: 0 原文鏈接 [收藏]

最近在做項目的時候，采用用Codesmith和Nettiers生成的框架來實現，生成的代碼核心是基于企業庫的。所以最近在惡補企業庫，對于緩存的學習當然是必不可少的，尤其是經常要用到得緩存依賴，這里我用到的是文件依賴來舉例子，其他的都大同小異，主要就是要實現ICacheItemExpiration中的返回值類型為bool類型的HasExpired方法，來控制到期與否，實現此方法是關鍵所在。下面是程序清單，歡迎大家指正：

step1 實現緩存到期接口，此類就為緩存項依賴的類，為緩存依賴的核心，尤其是其中HasExpired方法的定義，此類的核心就是使用lastCount是否變化來判斷緩存是否到期；如果有變化則HasExpired方法返回true,否則返回false。

Code
using System;
using System.Web;
using Microsoft.Practices.EnterpriseLibrary.Caching;

/// <summary>
///CacheItemDependency 的摘要說明
/// </summary>
public class CacheItemDependency : ICacheItemExpiration
{
    //依賴緩存項鍵
    private readonly string dependencyCacheKey;

    //依賴緩存項值
    private System.Int32 lastCount;

    #region Constructor
    /// <summary>
    /// 初始化依賴緩存項，如果此緩存管理對象存在，則取出緩存的數據；若不存在，就要對此緩存管理賦值
    /// </summary>
    /// <param name="cacheKey">依賴緩存項的鍵</param>
    public CacheItemDependency(string cacheKey)
    {
        dependencyCacheKey = cacheKey;
        ICacheManager cacheManager = CacheFactory.GetCacheManager();
        lastCount = Int32.MinValue;
        if (cacheManager != null)
        {
            if (cacheManager.Contains(cacheKey))
            {
                object o = cacheManager.GetData(cacheKey);
                if (o != null)
                {
                    this.lastCount = (int)o;
                }

                lastCount = (int)cacheManager.GetData(cacheKey);
            }
            else
            {
                cacheManager.Add(cacheKey, lastCount);
            }
        }

    }
    #endregion

    #region Properties
    public string DependencyCacheKey
    {
        get { return dependencyCacheKey; }
    }

    public System.Int32 LastCount
    {
        get { return lastCount; }
    }
    #endregion

    #region ICacheItemExpiration Members
    public bool HasExpired()
    {
        ICacheManager cacheManager = CacheFactory.GetCacheManager();
        if (cacheManager == null)
        {
            return true;
        }

        System.Int32 currentCount = (int)cacheManager.GetData(dependencyCacheKey);
        if (currentCount != lastCount)
        {
            return true;
        }
        else
        {
            return false;
        }
    }
    public void Notify()
    {
    }
    public void Initialize(CacheItem owningCacheItem)
    {
    }
    #endregion

}

step2 定義修改依賴項緩存的方法

Code
using System;
using System.Web;
using Microsoft.Practices.EnterpriseLibrary.Caching;

/// <summary>
///DataAccessUtil 的摘要說明
/// </summary>
public class DataAccessUtil
{
    public DataAccessUtil()
    {
        //
        //TODO: 在此處添加構造函數邏輯
        //
    }

    /// <summary>
    /// 更新所有以cacheKeys中元素為key的緩存項
    /// </summary>
    /// <param name="cacheKeys">緩存項的key的數組</param>
    public static void UpdateCacheDependency(string[] cacheKeys)
    {
        ICacheManager cacheManager = CacheFactory.GetCacheManager();
        foreach (string cacheKey in cacheKeys)
        {
            if (cacheManager != null && cacheManager.Contains(cacheKey))
            {
                int lastCount = (int)cacheManager.GetData(cacheKey);
                if (lastCount < Int32.MaxValue)
                {
                    lastCount++;
                }
                else
                {
                    lastCount = Int32.MinValue;
                }
                // 這一句的作用在于更新以cacheKey為key的緩存項,從而使依賴于此緩存項的緩存項失效.
                cacheManager.Add(cacheKey, lastCount);
            }
        }
    }
}

step3 測試實體，下面只是個簡單的測試，大家可以發散一下，寫出更加有復用性的方法。

Code
using System;
using System.Collections.Generic;
using System.Linq;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Microsoft.Practices.EnterpriseLibrary.Caching;

public partial class Test : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {
        if (!IsPostBack)
        {
            ICacheManager cacheManager = CacheFactory.GetCacheManager();
            cacheManager.Add("s", TextBox1.Text, CacheItemPriority.Normal, null, new CacheItemDependency("s1"));
            this.Label1.Text = cacheManager.GetData("s") as string;
        }
    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        ICacheManager cacheManager = CacheFactory.GetCacheManager();
        DataAccessUtil.UpdateCacheDependency(new string[] { "s1" });
        if (cacheManager.GetData("s") == null)
        {
            cacheManager.Add("s", TextBox1.Text, CacheItemPriority.Normal, null, new CacheItemDependency("s1"));
        }
        this.Label1.Text = cacheManager.GetData("s") as string;
    }
}