運用反射實現(xiàn)多層和多數(shù)據(jù)庫開發(fā)

1、現(xiàn)在很多項忖都須要為將來的擴展考慮，當(dāng)然數(shù)據(jù)庫也是一個很重我要的方面，擴展門c的provider,這就需耍反射技術(shù)，雖然會對性能有所影響，但是性價比還是很高的哦，從petshop和communityserver都可以看到反射技術(shù)啦，也可以說反射是最基木的啦,呵呵!他的老家是在system.reflection,當(dāng)我們要開工吋首先就是要把他抓出來.要實現(xiàn)這一功能我們當(dāng)然要知道provider的程序集，和工作的類名了，在多層架夠屮才能讓邏 輯和數(shù)據(jù)進行溝通,這樣也方便團隊開發(fā)的協(xié)條款發(fā)展，我們通過petshop和 communityserver兩個例子來說明一下.我們先看看petshop的反射技術(shù)

2、，在配制文件屮發(fā)現(xiàn)如下配制：v pet shop dal configuration settings -><add key= "webdal'1 value= "petshop.sqlserverdal'7><add key= "ordersdal" value= "petshop.sqlserverdal7><add key= "profiledal" value= "petshop.sqlprofiledal"/>其實只從配制文件中得到程序集

3、名稱，一般程序集就是類所在命名空間，也就是編譯后顯示的 dll名稱，那petshop是怎樣工作的，下面我們來看一下dataaccess類，這也】j說成一個工廠, 呵呵,我們來看一下代碼：1 using system.reflection;2 using system .configuration;33 曰國 namespace pet shop. dalfactory 56申由 iii < summary>7 iii this class is implemented following the abstract factory pattern to creat e the dal

4、 implementation8 iii specified from the configuration file9 / </summary>10申由 public sealed class dataaccess 12 / look up the dal implementation we should be using13 private static read only string path = configuratio nmanager.appsetti ngs” webdal”;14 private static read only string orderpath =

5、 con figuratio nmanager.appset tingshordersdalm;1516申申 private dataaccess() 1718：勺 public static petshop. i dal. i category createcategory() 19 string classname = path + ".category”；20 return (petshop.l dal. i category) assembly. load (path). creat el nstanc e(classname);21 f 2223審申 public stat

6、ic petshop.i dal.i inventory createlnventory() 24 string classname = path + tlnventory11;25 return (petshop.ldaljinventory)assembly.load(path)createlnstanc e(classname);26卜2728 *申 public static petshop.idal.litem createltem() 29 string classname = path + ".iterrt;30 return (petshop.l dal. 11 te

7、rn) assembly. load (path) .creat el n st a nce(cla ssname);31 3232 勻中 public static petshop. i dal. i order createorder() 33 string classname = orderpath + h.order*1;34 return (petshop.l dal. i order) assembly. load (order path). creat el nst an ce(classname);36卜3738 v 中 public static petshop. i dal

8、. i product createproduct() 39 string classname = path + product40 return (petshop.l dal. i product) assembly. load (path). creat el nstance (classname);41 f 4243卜44 l其中(petshop.l dal. i product) assembly. load (path) .creat el nstance( classname);就是將類進行反射，首先要載入程序集，然厲再創(chuàng)進類實例，通過靜態(tài)方法就可以玄接調(diào)用接口的 方法等，從而實現(xiàn)

9、了繼承接口的類的反射，同時也方便表現(xiàn)層的數(shù)據(jù)傳輸.下血我們來看一下communityserver是怎么實現(xiàn)的,cs是一個大彖極別的項h,所以他有 很h己擴展provider,那怎么樣才能讓他們工作呢？其實原理和上述的反射方法差不多，只不過 cs用的是object.gettyp()而達到這項功能.當(dāng)我第一次看到時，還一直為怎樣傳輸 connectionstring&dataowner而不解，厲來打開源數(shù)擁看了一卜-各個方法的注解后才理解.cs從自定的配制文件屮讀取provider節(jié)點并緩存，這在csconfiguration類屮可以發(fā)現(xiàn)，在 dataproviders類中就實現(xiàn)反射，通過

10、能構(gòu)造函數(shù)的反射查找最兀配的構(gòu)造函數(shù)對類進行實例化, 當(dāng)然當(dāng)他們遇到有connectionstring&dataowner兩參數(shù)的構(gòu)造函數(shù)時，就對其進行實例化， 從而達到對他們值的傳輸.1 /2 / <copyright company= "telligent systems">3 / copyright (c) telligent systems corporation. all rights reserved.4 / </copyright>5 /7 using system;8 using system.configuration;9

11、using system.io;10 using system.reflection;11 using system.web;12 using comm un ityserver.c on figuration;1313 namespace comm unity server. com pone nts15曰囹16白申 / < summary>17/ dataproviders is responible for loading and managing the various cs dataproviders1 8 - iii </summary>19 public

12、sealed class dataproviders20® 申21韜 / <summary>22 iiithis class cannot be instantiated23 _iii</summary>24 private dataproviders()25胡26卜27 i28 private static void getdatastoreparameters(provider dataprovider, out string connectionstring, out string databaseowner)29® 申30 databaseo

13、w ner = dataprovider.attributeshdatabaseow ner”;31 if(databaseowner = null 11 databaseowner.trim().length = = 0)32databaseow ner = con figurationsetti ngs.appsettingsdataprovider.attributes "databaseow nerst ring name”;33 i34 conn ectio nstring = dataprovider. attributes! hco nn ectio nstri ng”

14、;35 if(corrnectionstring = = null 11 cormectionstring.trim().length = = 0)36 corm ectio nstri ng = con figurationsetti ngs.appsetti ngsdataprovid er.attributesnc onn ectio nstri ngname”;37 f 38 i39誚iii < summary>40 / creates an in st a nee of the provider using activator this in stance sh ould

15、 be41 i / cached since it is an expesivie operation42 'iii </summary>43 public static object create in st a nce(provider dataprovider)44誚 45 /find the current attributes46 string cormectionstring = null; /dataprovider.attributeshconnection string*;47 string databaseowner = null;/ dataprovi

16、der.attributeshdatabaseow nerh;48 i49 getdatastoreparameters(dataprovider, out cormectionstring，out da tabaseowner);50 i51 /get the type52 type type = type.gettype(dataprovider.type);53 i54 object newobject=null;55 if(type != null)56帕newobject = activator.createlnstance(type,new object databaseowner

17、,connectionstring);58 f59 i60 if(newobject = = null) /if we can not create an instance, throw an e xceptio n61 providerexceptio n( dataprovider.name);62 i63 return newobject;64卜65 i66®申iii < summary>67 / creates and caches the constructor!nfo for the specified provider.68 - iii </summa

18、ry>69 public static constructorinfo creat econstructor info (provider dataprovi der)70® 申71 i72 / the assembly should be in bin or gac, so we simply need73 / to get an instance of the type74 i/75 csconfiguration config = csconfiguration.getconfig();76 constructorinfo providercnstr = null;77

19、try78誚79/string providertypename = (provider) configprovidersprovide rname).type;80type type = typegettype( dataprovider.type );type paramtypes = new type2;paramtypes0 = typeof(stri ng);paramtypes 1 = typeof(stri ng);providerc nstr = type. get construct or (param types);catchprovider except ion (dat

20、aprovider. name);if(providerc nstr= n ull)providerexcepti on( dataprovider.name);return providercnstr;/ < summary>iii creates an in st a nee of the specified provider using the cached/ constructorlnfo from createconstructorlnfoiii </summary>public static object invoke(provider dataprovid

21、er)object param array = new object2;string dbowner = null; string connstring = null;getdatastoreparameters(dataprovider, out conn string, out dbow ne param array0 = dbow ner;param array1 = conn stri ng;return createc on structorlnfo(dataprovider).! nvoke( param array);# region exceptionprivate static void providerexception(string