运用反射实现多层和多数据库开发.doc

现在很多项目都须要为将来的扩展考虑,当然数据库也是一个很重我要的方面,扩展自己的Provider,这就需要反射技术,虽然会对性能有所影响,但是性价比还是很高的哦,从PetShop和CommunityServer都可以看到反射技术啦,也可以说反射是最基本的啦,呵呵!他的老家是在System.Reflection,当我们要开工时首先就是要把他抓出来.要实现这一功能我们当然要知道Provider的程序集,和工作的类名了,在多层架够中才能让逻辑和数据进行沟通,这样也方便团队开发的协条款发展,我们通过PetShop和CommunityServer两个例子来说明一下. 我们先看看PetShop的反射技术,在配制文件中发现如下配制: 其实只从配制文件中得到程序集名称,一般程序集就是类所在命名空间,也就是编译后显示的DLL名称,那PetShop是怎样工作的,下面我们来看一下DataAccess类,这也可说成一个工厂,呵呵,我们来看一下代码:1usingSystem.Reflection;2usingSystem.Configuration;34namespacePetShop.DALFactory56/*/7/ThisclassisimplementedfollowingtheAbstractFactorypatterntocreatetheDALimplementation8/specifiedfromtheconfigurationfile9/10publicsealedclassDataAccess1112/LookuptheDALimplementationweshouldbeusing13privatestaticreadonlystringpath=ConfigurationManager.AppSettingsWebDAL;14privatestaticreadonlystringorderPath=ConfigurationManager.AppSettingsOrdersDAL;1516privateDataAccess()1718publicstaticPetShop.IDAL.ICategoryCreateCategory()19stringclassName=path+.Category;20return(PetShop.IDAL.ICategory)Assembly.Load(path).CreateInstance(className);212223publicstaticPetShop.IDAL.IInventoryCreateInventory()24stringclassName=path+.Inventory;25return(PetShop.IDAL.IInventory)Assembly.Load(path).CreateInstance(className);262728publicstaticPetShop.IDAL.IItemCreateItem()29stringclassName=path+.Item;30return(PetShop.IDAL.IItem)Assembly.Load(path).CreateInstance(className);313233publicstaticPetShop.IDAL.IOrderCreateOrder()34stringclassName=orderPath+.Order;35return(PetShop.IDAL.IOrder)Assembly.Load(orderPath).CreateInstance(className);363738publicstaticPetShop.IDAL.IProductCreateProduct()39stringclassName=path+.Product;40return(PetShop.IDAL.IProduct)Assembly.Load(path).CreateInstance(className);41424344 其中(PetShop.IDAL.IProduct)Assembly.Load(path).CreateInstance(className);就是将类进行反射,首先要载入程序集,然后再创进类实例,通过静态方法就可以直接调用接口的方法等,从而实现了继承接口的类的反射,同时也方便表现层的数据传输. 下面我们来看一下CommunityServer是怎么实现的,CS是一个大象极别的项目,所以他有很自己扩展Provider,那怎么样才能让他们工作呢?其实原理和上述的反射方法差不多,只不过CS用的是Object.GetTyp()而达到这项功能.当我第一次看到时,还一直为怎样传输ConnectionString&DataOwner而不解,后来打开源数据看了一下各个方法的注解后才理解.CS从自定的配制文件中读取Provider节点并缓存,这在CSConfiguration类中可以发现,在DataProviders类中就实现反射,通过能构造函数的反射查找最匹配的构造函数对类进行实例化,当然当他们遇到有ConnectionString&DataOwner两参数的构造函数时,就对其进行实例化,从而达到对他们值的传输. DataProviders1/-2/3/Copyright(c)TelligentSystemsCorporation.Allrightsreserved.4/5/-67usingSystem;8usingSystem.Configuration;9usingSystem.IO;10usingSystem.Reflection;11usingSystem.Web;12usingCommunityServer.Configuration;1314namespaceCommunityServer.Components1516/*/17/DataProvidersisresponibleforloadingandmanagingthevariousCSDataProviders18/19publicsealedclassDataProviders2021/*/22/Thisclasscannotbeinstantiated23/24privateDataProviders()25262728privatestaticvoidGetDataStoreParameters(ProviderdataProvider,outstringconnectionString,outstringdatabaseOwner)2930databaseOwner=dataProvider.AttributesdatabaseOwner;31if(databaseOwner=null|databaseOwner.Trim().Length=0)32databaseOwner=ConfigurationSettings.AppSettingsdataProvider.AttributesdatabaseOwnerStringName;3334connectionString=dataProvider.AttributesconnectionString;35if(connectionString=null|connectionString.Trim().Length=0)36connectionString=ConfigurationSettings.AppSettingsdataProvider.AttributesconnectionStringName;373839/*/40/CreatesaninstanceoftheproviderusingActivator.Thisinstanceshouldbe41/cachedsinceitisanexpesivieoperation42/43publicstaticobjectCreateInstance(ProviderdataProvider)4445/Findthecurrentattributes46stringconnectionString=null;/dataProvider.AttributesconnectionString;47stringdatabaseOwner=null;/dataProvider.AttributesdatabaseOwner;4849GetDataStoreParameters(dataProvider,outconnectionString,outdatabaseOwner);5051/Getthetype52Typetype=Type.GetType(dataProvider.Type);5354objectnewObject=null;55if(type!=null)5657newObject=Activator.CreateInstance(type,newobjectdatabaseOwner,connectionString);585960if(newObject=null)/Ifwecannotcreateaninstance,throwanexception61ProviderException(dataProvider.Name);6263returnnewObject;646566/*/67/CreatesandCachestheConstructorInfoforthespecifiedprovider.68/69publicstaticConstructorInfoCreateConstructorInfo(ProviderdataProvider)707172/TheassemblyshouldbeinbinorGAC,sowesimplyneed73/togetaninstanceofthetype74/75CSConfigurationconfig=CSConfiguration.GetConfig();76ConstructorInfoproviderCnstr=null;77try7879/stringproviderTypeName=(Provider)config.ProvidersproviderName).Type;80Typetype=Type.GetType(dataProvider.Type);8182/Insertthetypeintothecache83/84TypeparamTypes=newType2;85paramTypes0=typeof(string);86paramTypes1=typeof(string);8788providerCnstr=type.GetConstructor(paramTypes);899091catch9293ProviderException(dataProvider.Name);949596if(providerCnstr=null)97ProviderException(dataProvider.Name);9899returnproviderCnstr;100101102/*/103/CreatesaninstanceofthespecifiedproviderusingtheCached104/ConstructorInfofromCreateConstructorInfo105/106publicstaticobjectInvoke(ProviderdataProvider)107108objectparamArray=newobject2;109110111stringdbOwner=null;112stringconnstring=null;113114GetDataStoreParameters(dataProvider,outconnstring,outdbOwner);115116paramArray0=dbOwner;117paramArray1=connstring;118119returnCreateConstructorInfo(dataProvider).Invoke(paramArray);120121122Exception#regionException123privatestaticvoidProviderException(stringproviderName)124125CSConfigurationconfig=CSConfiguration.GetConfig();126HttpContextcontext=HttpContext.Current;127if(context!=null)128129130/Wecantloadthedataprovider131/132StreamReaderreader=newStreamReader(context.Server.MapPath(/Languages/+config.DefaultLanguage+/errors/DataProvider.htm);133stringhtml=reader.ReadToEnd();134reader.Close();135136html=html.Replace(DATAPROVIDERCLAS