利用AOP重构代码
????? AOP是什么？
??? AOP是OOP的延續，Aspect Oriented Programming的縮寫，即面向方面編程。AOP是GoF設計模式的延續，設計模式追求的是調用者和被調用者之間的解耦，AOP也是這種目標的一 種實現。
??????案例:在應用程序中,我們經常會對某一段程序做異常處理,或者是把一個方法的調用所消耗的時間體現在日志中,如果我們對每個方法都寫具體的實現,我想并不是一件輕松的事情。對于異常處理來講，其實我們平常編程很少去捕獲具體的異常，當然特殊程序除外，例如客戶端捕獲WCF異常時最好捕獲CommunicationException，TimeoutException，Exception。否則一般都會直接捕獲Exception，因為很多異常往往是意料之外的異常。對于記錄方法調用時間問題，我想也非常麻煩，下面例子簡單的展示了記錄時間：當你需要對多個方法都需要記錄時間時，這些代碼往往讓人感覺有重構的必要。
???
Stopwatch?sw?=?new?Stopwatch();???sw.Start();
???//方法執行.....
???sw.Stop();
???WebLog.SquareLog.CommonLogger.Error("取積分廣場首頁酒店數據用時:"+sw.ElapsedMilliseconds?.ToString?()+"毫秒");
?
??? ? 上面的記錄方法調用用時，如果抽象出來，其實有下列特性：
????? 1:不是具體訪問類的首要或主要功能，訪問類主要功能是業務邏輯處理。
????? 2：具體訪問類的主要功能可以獨立、區分開來的。
????? 3：是這個系統的一個縱向切面，涉及多個類、多個類的方法。示意圖如下：
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?????
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????? aspect:? 新的程序結構關注系統的縱向切面，例如這里的異常處理以及方法調用時間記錄，這個新的程序結構就是aspect（方面）,方面（aspect）應該有以下職責：提供一些必備的功能，對被訪問對象實現特有功能,以保證所以方法在被執行時都能正常的執行異常處理或者是其它的功能。
???? ?AOP應用范圍
????? 1：Authentication 權限
???? ?2：Error handling 錯誤處理
????? 3：logging, tracing, profiling and monitoring 記錄跟蹤 優化 校準
??? ??......
???? AOP具體實現：主要是利用泛型委托來實現AOP思想。但泛型委托有一個局限就是最多支持四個參數，當你的方法超過四個時就不太好應用AOP重構了。我最近分析了有以下三個地方我們可以對代碼進行優化：
???? 第一：普通方法異常處理：ErrorHandler類,實現類參考第二或者是第三。
??????????? 客戶端調用：
?????????
???????????list?=?ErrorWCFHandler?.Invoke<ISearchHotelForSquare,?List<HotelGenericInfo>>(cli,?proxy?=>?proxy.GetHotelGenericListForSquare(requestInfo).ToList()?);?
?
???? 第二：客戶端調用WCF的異常處理：ErrorWCFHandler。
??????????? 代碼：
代碼 public??class?ErrorWCFHandler????{
???????public?static?void?Invoke<TContract>(TContract?proxy,?Action<TContract>?action,?string?MethodElapsedTimeText,?string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????try
????????????{
????????????????action(proxy);
????????????????(proxy?as?ICommunicationObject).Close();
????????????}
????????????catch?(CommunicationException?ex)
????????????{
????????????????(proxy?as?ICommunicationObject).Abort();
????????????????//Handle?Exception?????????????
????????????????//throw;
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????catch?(TimeoutException?ex)
????????????{
????????????????(proxy?as?ICommunicationObject).Abort();
????????????????//Handle?Exception?????????
????????????????//throw;
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception????????
????????????????//(proxy?as?ICommunicationObject).Close();??????
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText?+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????}
???????public?static?TReturn?Invoke<TContract,?TReturn>(TContract?proxy,?Func<TContract,?TReturn>?func,?string?MethodElapsedTimeText,?string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????TReturn?returnValue?=?default(TReturn);
????????????try
????????????{
????????????????returnValue?=?func(proxy);
????????????}
????????????catch?(CommunicationException?ex)
????????????{
????????????????(proxy?as?ICommunicationObject).Abort();
????????????????//Handle?Exception?????
????????????????//throw;
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????catch?(TimeoutException?ex)
????????????{
????????????????(proxy?as?ICommunicationObject).Abort();
????????????????//Handle?Exception???????
????????????????//throw;
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception??
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText?+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????????return?returnValue;
????????}
????}
?
????????? 客戶端調用：
??????????
???????????string?ErrorMethodText="取積分廣場首頁酒店數據異常:";
???????????list?=?ErrorWCFHandler?.Invoke<ISearchHotelForSquare,?List<HotelGenericInfo>>(cli,?proxy?=>?proxy.GetHotelGenericListForSquare(requestInfo).ToList
(),ComputationTimeText?,ErrorMethodText?);??
?
?? ?? 第三：記錄方法調用時間，這中間也增加了異常處理：ErrorAndComputationTimeHandler
??????????? 代碼：
????{
????????public?static?void?Invoke<TContract>(TContract?proxy,?Action<TContract>?action,?string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????try
????????????{
????????????????action(proxy);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????}
????????public?static?void?Invoke<TContract,?TContract2>(TContract?proxy,?TContract2?proxy2,?Action<TContract,?TContract2>?action,?string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????try
????????????{
????????????????action(proxy,?proxy2);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????}
????????public?static?void?Invoke<TContract,?TContract2,?TContract3>(TContract?proxy,?TContract2?proxy2,?TContract3?proxy3,?Action<TContract,?TContract2,?TContract3>?action,?string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????try
????????????{
????????????????action(proxy,?proxy2,?proxy3);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????}
????????public?static?void?Invoke<TContract,?TContract2,?TContract3,?TContract4>(TContract?proxy,?TContract2?proxy2,?TContract3?proxy3,?TContract4?proxy4,?Action<TContract,?TContract2,?TContract3,?TContract4>?action,??string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????try
????????????{
????????????????action(proxy,?proxy2,?proxy3,?proxy4);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????}
????????public?static?TReturn?Invoke<TContract,?TReturn>(TContract?proxy,?Func<TContract,?TReturn>?func,??string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????TReturn?returnValue?=?default(TReturn);
????????????try
????????????{
????????????????returnValue?=?func(proxy);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????????return?returnValue;
????????}
????????public?static?TReturn?Invoke<TContract,?TContract2,?TReturn>(TContract?proxy,?TContract2?proxy2,?Func<TContract,?TContract2,?TReturn>?func,??string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????TReturn?returnValue?=?default(TReturn);
????????????try
????????????{
????????????????returnValue?=?func(proxy,?proxy2);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????????return?returnValue;
????????}
????????public?static?TReturn?Invoke<TContract,?TContract2,?TContract3,?TReturn>(TContract?proxy,?TContract2?proxy2,?TContract3?proxy3,?Func<TContract,?TContract2,?TContract3,?TReturn>?func,??string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????TReturn?returnValue?=?default(TReturn);
????????????try
????????????{
????????????????returnValue?=?func(proxy,?proxy2,?proxy3);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????????return?returnValue;
????????}
????????public?static?TReturn?Invoke<TContract,?TContract2,?TContract3,?TContract4,?TReturn>(TContract?proxy,?TContract2?proxy2,?TContract3?proxy3,?TContract4?proxy4,?Func<TContract,?TContract2,?TContract3,?TContract4,?TReturn>?func,??string?MethodElapsedTimeText,string?MethodErrorText)
????????{
????????????Stopwatch?sw?=?new?Stopwatch();
????????????sw.Start();
????????????TReturn?returnValue?=?default(TReturn);
????????????try
????????????{
????????????????returnValue?=?func(proxy,?proxy2,?proxy3,?proxy4);
????????????}
????????????catch?(Exception?ex)
????????????{
????????????????//Handle?Exception???
????????????????WebLog.SquareLog.CommonLogger.Error(MethodErrorText?+?ex.ToString());
????????????}
????????????sw.Stop();
????????????WebLog.SquareLog.CommonLogger.Error(MethodElapsedTimeText??+?sw.ElapsedMilliseconds.ToString()?+?"毫秒");
????????????return?returnValue;
????????}
????}
?
??????????? 客戶端調用：?????
代碼 string?ComputationTimeText?=?"取酒店是否在積分廣場首頁推薦數據耗時:";????????????string?ErrorMethodText?=?"取酒店是否在積分廣場首頁推薦數據異常:";
????????????string?conn?=?WebConfig.DaoConfig.MisMasterDBReadConnectionString;
????????????HotelRecommendInfo?=?ErrorAndComputationTimeHandler.Invoke<HotelRequestInfo,?string,?List<HotelGenericInfo>>(requestInfo,?conn,?SearchRecommendHotelData,?ComputationTimeText,?ErrorMethodText);
????
?????? AOP的優勢：
1:上述應用范例在沒有使用AOP情況下，也能解決，但是，AOP可以讓我們從一個更高的抽象概念來理解軟件系統。可以這么說：因為使用AOP結構，對于一個大型復雜系統來說可以簡化不少代碼。
2:并不是所有的人都需要關心AOP，使得其它開發人員有更多精力去關注自己的業務邏輯。
?
作者：姜敏
出處：http://www.cnblogs.com/aspnet2008/?
轉載于:https://www.cnblogs.com/ASPNET2008/archive/2010/04/18/1714528.html
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