大哥们帮忙看看这段没错的代码
using System;
using System.Reflection;
using System.Collections.Specialized;
using System.Configuration.Provider;
using System.Data;
using System.Web.Caching;
using System.Web;
using System.Web.Configuration;
using System.Configuration;
namespace Commerce.Providers {
public abstract class CatalogProvider : System.Configuration.Provider.ProviderBase
{
static CatalogProvider _instance;
static object padLock;
public static CatalogProvider Instance {
get {
CatalogProvider tempInstance;
if (_instance == null)
padLock = new object();
lock (padLock) {
tempInstance = LoadProvider();
_instance = tempInstance;
}
return _instance;
}
}
static CatalogProvider LoadProvider() {
// Get the names of the providers
// Use the cache because the reflection used later is expensive
Cache cache = System.Web.HttpRuntime.Cache;
string cacheKey = null;
CatalogProvider _instanceLoader;
CatalogProviderConfiguration config = CatalogProviderConfiguration.GetConfig();
cacheKey = "CatalogProvider:: " + config.DefaultProvider;
object oProvider = cache.Get(cacheKey);
if (oProvider != null) {
_instanceLoader = (CatalogProvider)oProvider;
} else {
try {
// Read the configuration specific information for this provider
Provider CatalogProvider = (Provider)config.Providers[config.DefaultProvider];
// The assembly should be in \bin or GAC
Type type = Type.GetType(CatalogProvider.Type);
_instanceLoader = (CatalogProvider)Activator.CreateInstance(type);
// Initialize the provider with the attributes.
string cStringName = CatalogProvider.Attributes[ "connectionStringName "];
string cString = System.Configuration.ConfigurationManager.ConnectionStrings[cStringName].ConnectionString;
CatalogProvider.Attributes.Add( "connectionString ", cString);
_instanceLoader.Initialize(CatalogProvider.Name, CatalogProvider.Attributes);
//pop it into the cache to keep out site from running into the ground :)
cache.Insert(cacheKey, _instanceLoader);
} catch (Exception e) {
throw new Exception( "Unable to load provider ", e);
}
}
return _instanceLoader;
}
///LoadProvider和Instance 各实现什么的功能？
这里为什么能使用CatalogProvider ？
[解决办法]
public static CatalogProvider Instance {
的操作就是得到一个CatalogProvider 的对象
LoadProvider()是这个对象的 现实原理
这里应该是 用于CatalogProvider 对象的cache缓存的一个实现
[解决办法]
public abstract class CatalogProvider : System.Configuration.Provider.ProviderBase
{
static CatalogProvider _instance; //单件模式
static object padLock; //同步锁
public static CatalogProvider Instance { //单件模式
get {
CatalogProvider tempInstance;
if (_instance == null)
padLock = new object();
lock (padLock) {
tempInstance = LoadProvider();
_instance = tempInstance;
}
return _instance;
}
}
static CatalogProvider LoadProvider() {
// Get the names of the providers
// Use the cache because the reflection used later is expensive
Cache cache = System.Web.HttpRuntime.Cache;
string cacheKey = null;
CatalogProvider _instanceLoader;
CatalogProviderConfiguration config = CatalogProviderConfiguration.GetConfig();
cacheKey = "CatalogProvider:: " + config.DefaultProvider;
object oProvider = cache.Get(cacheKey); //试图从缓存中获取对象
if (oProvider != null) {
_instanceLoader = (CatalogProvider)oProvider;
} else {
//如果缓存中没有，就实例化一个
try {
// Read the configuration specific information for this provider
Provider CatalogProvider = (Provider)config.Providers[config.DefaultProvider];
// The assembly should be in \bin or GAC
Type type = Type.GetType(CatalogProvider.Type);
_instanceLoader = (CatalogProvider)Activator.CreateInstance(type);
// Initialize the provider with the attributes.
string cStringName = CatalogProvider.Attributes[ "connectionStringName "];
string cString = System.Configuration.ConfigurationManager.ConnectionStrings[cStringName].ConnectionString;
CatalogProvider.Attributes.Add( "connectionString ", cString);
_instanceLoader.Initialize(CatalogProvider.Name, CatalogProvider.Attributes);
//pop it into the cache to keep out site from running into the ground :)
cache.Insert(cacheKey, _instanceLoader);
} catch (Exception e) {
throw new Exception( "Unable to load provider ", e);
}
}
return _instanceLoader;
}
