建立自定義的數(shù)據(jù)驅(qū)動的本地化資源provider

更新時間：2010年06月17日 13:56:13 作者：

本文探討了自定義的本地化資源提供者.如果想用一個可替代系統(tǒng)的資源處理方案,例如把所有的資源放入數(shù)據(jù)庫中,而不是放在分散的資源文件里,你可以自定義一個resource provider.

原文很長,為了便于閱讀和理解,特將該文章改寫成通俗易懂而且內(nèi)容精煉的中文.

預(yù)備知識:系統(tǒng)默認(rèn)的處理資源和本地化的方法是使用resx文件存儲資源.

要使用自定義的resource provider,需要2個步驟:
a) 修改web.config 文件,以便系統(tǒng)使用自定義的資源提供者
b) 建立自定義資源提供者類,最少包括3個:
1.ResourceProviderFactory,工廠類,用來建立ResourceProvider對象.
2.ResourceProvider,實現(xiàn)IResourceProvider,IImplicitResourceProvider,IwwResourceProvider 接口.
3.ResourceReader 實現(xiàn)IResourceReader.

修改web.config 文件,以使用自定義的資源提供者。

復(fù)制代碼代碼如下:

 
<configuration> 
<system.web> 
<globalization resourceProviderFactoryType="Westwind.Globalization.DbSimpleResourceProviderFactory,Westwind.Globalization" /> 
</system.web> 
</configuration> 

建立自定義資源提供者類:
1.工廠類

復(fù)制代碼代碼如下:

 
[DesignTimeResourceProviderFactoryAttribute(typeof(DbDesignTimeResourceProviderFactory))] 
public class DbSimpleResourceProviderFactory : ResourceProviderFactory 
{ 

public override IResourceProvider CreateGlobalResourceProvider(string classname) 
{ 
return new DbSimpleResourceProvider(null, classname); 
} 


public override IResourceProvider CreateLocalResourceProvider(string virtualPath) 
{ 

string ResourceSetName = DbResourceConfiguration.Current.StripVirtualPath(virtualPath); 
return new DbSimpleResourceProvider(null,ResourceSetName.ToLower()); 
} 
} 

2.提供者類

復(fù)制代碼代碼如下:

 
public class DbSimpleResourceProvider : IResourceProvider, IImplicitResourceProvider 
{ 

private string _ResourceSetName; 


private IDictionary _resourceCache; 


private DbSimpleResourceProvider() 
{ } 


public DbSimpleResourceProvider(string virtualPath, string className) 
{ 
_ResourceSetName = className; 
} 



private IDictionary GetResourceCache(string cultureName) 
{ 
if (cultureName == null) 
cultureName = ""; 


if (this._resourceCache == null) 
this._resourceCache = new ListDictionary(); 


IDictionary Resources = this._resourceCache[cultureName] as IDictionary; 
if (Resources == null) 
{ 
// *** DEPENDENCY HERE (#1): Using DbResourceDataManager to retrieve resources 


// *** Use datamanager to retrieve the resource keys from the database 
DbResourceDataManager Data = new DbResourceDataManager(); 
Resources = Data.GetResourceSet(cultureName as string, this._ResourceSetName); 
this._resourceCache[cultureName] = Resources; 
} 


return Resources; 
} 



public void ClearResourceCache() 
{ 
this._resourceCache.Clear(); 
} 



object IResourceProvider.GetObject(string ResourceKey, CultureInfo Culture) 
{ 
string CultureName = null; 
if (Culture != null) 
CultureName = Culture.Name; 
else 
CultureName = CultureInfo.CurrentUICulture.Name; 


return this.GetObjectInternal(ResourceKey, CultureName); 
} 



object GetObjectInternal(string ResourceKey, string CultureName) 
{ 
IDictionary Resources = this.GetResourceCache(CultureName); 

object value = null; 
if (Resources == null) 
value = null; 
else 
value = Resources[ResourceKey]; 

// *** If we're at a specific culture (en-Us) and there's no value fall back 
// *** to the generic culture (en) 
if (value == null && CultureName.Length > 3) 
{ 
// *** try again with the 2 letter locale 
return GetObjectInternal(ResourceKey,CultureName.Substring(0,2) ); 
} 


// *** If the value is still null get the invariant value 
if (value == null) 
{ 
Resources = this.GetResourceCache(""); 
if (Resources == null) 
value = null; 
else 
value = Resources[ResourceKey]; 
} 


// *** If the value is still null and we're at the invariant culture 
// *** let's add a marker that the value is missing 
// *** this also allows the pre-compiler to work and never return null 
if (value == null && string.IsNullOrEmpty(CultureName)) 
{ 
// *** No entry there 
value = ""; 


// *** DEPENDENCY HERE (#2): using DbResourceConfiguration and DbResourceDataManager to optionally 
// add missing resource keys 


// *** Add a key in the repository at least for the Invariant culture 
// *** Something's referencing but nothing's there 
if (DbResourceConfiguration.Current.AddMissingResources) 
new DbResourceDataManager().AddResource(ResourceKey, value.ToString(), "", this._ResourceSetName); 


} 


return value; 
} 

3.Reader類

復(fù)制代碼代碼如下:

 
public class DbSimpleResourceReader : IResourceReader 
{ 
private IDictionary _resources; 


public DbSimpleResourceReader(IDictionary resources) 
{ 
_resources = resources; 
} 
IDictionaryEnumerator IResourceReader.GetEnumerator() 
{ 
return _resources.GetEnumerator(); 
} 
void IResourceReader.Close() 
{ 
} 
IEnumerator IEnumerable.GetEnumerator() 
{ 
return _resources.GetEnumerator(); 
} 
void IDisposable.Dispose() 
{ 
} 
} 