private static DistributeCacheProvider InstantiateProvider(ProviderSettings providerSettings, CacheSettings cacheSettings)
{
DistributeCacheProvider provider = null;
try
{
if (providerSettings == null)
{
throw new ArgumentNullException("providerSettings");
}
string providerSettingTypeName = providerSettings.Type == null ? null : providerSettings.Type.Trim();
if (string.IsNullOrEmpty(providerSettingTypeName))
{
throw new ArgumentException(String.Format("名称为 {0} 的分布式缓存提供程序缺少类型定义。", providerSettings.Name), "providerSettings");
}
Type providerSettingType = Type.GetType(providerSettingTypeName, true, true);
if (!typeof(DistributeCacheProvider).IsAssignableFrom(providerSettingType))
{
throw new ArgumentException(String.Format("分布式缓存提供程序 {0} 必须实现或继承 {1}。", providerSettings.Name, typeof(DistributeCacheProvider).ToString()));
}
provider = (DistributeCacheProvider)Activator.CreateInstance(providerSettingType, providerSettings.CurrentConfiguration);
provider.cacheSettings = cacheSettings;
NameValueCollection parameters = providerSettings.Parameters;
NameValueCollection config = new NameValueCollection(parameters.Count, StringComparer.Ordinal);
foreach (string s in parameters)
{
config[s] = parameters[s];
}
provider.Initialize(providerSettings.Name, config);
}
catch (Exception exception)
{
if (exception is ConfigurationException)
{
throw;
}
throw new ConfigurationErrorsException(exception.Message, exception, providerSettings.ElementInformation.Properties["type"].Source, providerSettings.ElementInformation.Properties["type"].LineNumber);
}
return provider;
}
private void configService_ConfigFileChanged(object sender, ConfigFileChangedEventArgs e)
{
if (e.ConfigFileType == ConfigFileType.Cache)
{
CacheSettings oldSettings = instance; // 临时保存当前正确的实例
// 在配置文件变化时， 结合 CacheSettings.Instance 单例模式，通过将实例对象设置为 null，暂时阻止对单例实例的访问
lock (syncForSettings)
{
instance = null; // 将 instance 设置为 null，暂时阻止对单例实例的访问
CacheSettings newSettings = null;
try
{
newSettings = new CacheSettings();
instance = newSettings; // 启用新的配置
}
catch (Exception err)
{
instance = oldSettings; // 恢复为最近一次正确的配置
XMS.Core.Container.LogService.Warn("在响应配置文件变化的过程中发生错误，仍将使用距变化发生时最近一次正确的配置。", Logging.LogCategory.Configuration, err);
}
// 成功应用新的配置后，处理配置文件变化监听事件
if (instance != oldSettings)
{
if (oldSettings != null)// 为旧实例移除配置变化监听事件
{
// 这里不能通过 Dispose 释放事件，因为 oldSettings 的实例有可能被在缓存相关操作方法里通过局部变量引用，后面仍然有可能继续使用
// 因此这里手动释放旧实例的监听事件
oldSettings.ConfigService.ConfigFileChanged -= oldSettings.configFileChangedEventHandler;
}
}
}
// 单例实例发生变化后，在 lock (syncForSettings) 语句之外清空缓存，以避免与 Clear 过程中发生死锁（因为锁定过程中会访问 CacheSettings 的单例实例）
if (instance != oldSettings)
{
LocalCacheManager.Instance.Clear();
}
}
}
private static void InstantiateProviders(ProviderSettingsCollection configProviders, ProviderCollection providers, CacheSettings cacheSettings)
{
foreach (ProviderSettings settings in configProviders)
{
providers.Add(InstantiateProvider(settings, cacheSettings));
}
}
