C#实现自动化Log日志

在开发项目的时候，我们不免要使用Log记录日志，使用最多的是Log4Net和EntLib Log，在需要记录日志的代码处加入log.Write(日志信息)，假设我需要跟踪业务方法，记录方法的传递参数，执行时间，返回数据等；或者我需要查看方法的调用关系，希望进入方法的时候自动记录参数信息，出方法时记录结果和执行时间信息。这时就是一个典型的AOP运用，Java在AOP方面是很容易实现的，因为java有类加载器。但是.Net在AOP方面就不怎么容易，严格意义上.Net没有真正的AOP。这话并不代表.Net不能实现AOP，比如：PostSharp和Enterprise library就能实现。

先介绍一下PostSharp，我们知道.net代码将编译成MSIL（微软中间语言），然后CPU将MSIL的exe文件生成本地CPU的二进制文件格式，PostSharp就是在编译过程中加入IL代码，因而完成AOP功能。
缺点：编译器需要PostSharp组件，维护代码困难，因为IL代码不好识别；
优点：使用方便（PostSharp2是收费版，破解也比较方便，在此不介绍破解）

这里我重点介绍如何使用Enterprise Library实现自动化Log。
1.首先我们需要下载Enterprise Library，最新为5.0版本；
2.新建一个控制台项目，并添加以下程序集
Microsoft.Practices.EnterpriseLibrary.Common
Microsoft.Practices.EnterpriseLibrary.Logging
Microsoft.Practices.EnterpriseLibrary.PolicyInjection
Microsoft.Practices.ServiceLocation
Microsoft.Practices.Unity
Microsoft.Practices.Unity.Interception
3.添加AutoLogCallHandler类，实现ICallHandler接口
这个类是执行调用目标方法，在调用目标方法前获取方法的参数信息，并用EntLib Log记录日志；
方法结束后，再次记录日志，并统计执行时间和异常处理

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.Unity.InterceptionExtension; using Microsoft.Practices.EnterpriseLibrary.Logging; using Microsoft.Practices.EnterpriseLibrary.Common.Configuration; using System.Diagnostics; using System.Reflection; namespace AutoLog { public class AutoLogCallHandler:ICallHandler { private LogWriter logWriter = EnterpriseLibraryContainer.Current.GetInstance(); public AutoLogCallHandler() { } public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext) { StringBuilder sb = null; ParameterInfo pi = null; string methodName = input.MethodBase.Name; logWriter.Write(string.Format("Enter method " + methodName)); if (input.Arguments != null && input.Arguments.Count > 0) { sb = new StringBuilder(); for (int i = 0; i < input.Arguments.Count; i++) { pi = input.Arguments.GetParameterInfo(i); sb.Append(pi.Name).Append(" : ").Append(input.Arguments[i]).AppendLine(); } logWriter.Write(sb.ToString()); } Stopwatch sw = new Stopwatch(); sw.Start(); IMethodReturn result = getNext()(input, getNext); //如果发生异常则，result.Exception != null if (result.Exception != null) { logWriter.Write("Exception:" + result.Exception.Message); //必须将异常处理掉，否则无法继续执行 result.Exception = null; } sw.Stop(); logWriter.Write(string.Format("Exit method {0}, use {1}.",methodName, sw.Elapsed)); return result; } public int Order { get; set; } } }

4.要自动化日志就需要创建一个标记属性，指定方法能自动进行日志
这里就创建AutoLogCallHandlerAttribute标记属性

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.Unity.InterceptionExtension; using Microsoft.Practices.EnterpriseLibrary.Logging; using System.Diagnostics; using Microsoft.Practices.EnterpriseLibrary.Common.Configuration; namespace AutoLog { public class AutoLogCallHandlerAttribute:HandlerAttribute { public override ICallHandler CreateHandler(Microsoft.Practices.Unity.IUnityContainer container) { return new AutoLogCallHandler() { Order = this.Order }; } } }

5.创建实体类
注意：我在Work和ToString方法上方加上了AutoLogCallHandler属性，它是AutoLogCallHandlerAttribute的简写形式。用以指示这两个方法用AutoLogCallHandler的Invoke来处理。

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.Unity; namespace AutoLog { public class Employee : MarshalByRefObject { public Employee() {} public string Name { get; set; } [AutoLogCallHandler()] public void Work() { Console.WriteLine("Now is {0},{1} is working hard!",DateTime.Now.ToShortTimeString(),Name); throw new Exception("Customer Exception"); } [AutoLogCallHandler()] public override string ToString() { return string.Format("I'm {0}.",Name); } } }

6.测试代码
注意：必须使用PolicyInjection.Create()来创建对象，不然无法实现。

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.EnterpriseLibrary.PolicyInjection; using Microsoft.Practices.Unity; using Microsoft.Practices.EnterpriseLibrary.Logging; using Microsoft.Practices.EnterpriseLibrary.Common.Configuration; namespace AutoLog { class Program { private static LogWriter logWriter = EnterpriseLibraryContainer.Current.GetInstance(); static void Main(string[] args) { Employee emp = PolicyInjection.Create(); emp.Name = "Lele"; emp.Work(); Console.WriteLine(emp); } } }

7.还需要用EntLib的配置工具完成Log配置，将Log信息写入Trace.log文件中

好了，测试一下，控制台输入：
Now is 14:03,Lele is working hard!
I'm Lele.
再看看Trace.log文件内容：

---------------------------------------- Timestamp: 2012/3/19 6:03:00 Message: Enter method Work Category: General Priority: -1 EventId: 1 Severity: Information Title: Machine: PC4 App Domain: AutoLog.exe ProcessId: 4200 Process Name: D:\Codes\Enterprise Library\Enterprise Library Demos\PIAB\Demo\AutoLog\bin\Debug\AutoLog.exe Thread Name: Win32 ThreadId:4000 Extended Properties: ---------------------------------------- ---------------------------------------- Timestamp: 2012/3/19 6:03:00 Message: Exception:Customer Exception Category: General Priority: -1 EventId: 1 Severity: Information Title: Machine: PC4 App Domain: AutoLog.exe ProcessId: 4200 Process Name: D:\Codes\Enterprise Library\Enterprise Library Demos\PIAB\Demo\AutoLog\bin\Debug\AutoLog.exe Thread Name: Win32 ThreadId:4000 Extended Properties: ---------------------------------------- ---------------------------------------- Timestamp: 2012/3/19 6:03:00 Message: Exit method Work, use 00:00:00.0024272. Category: General Priority: -1 EventId: 1 Severity: Information Title: Machine: PC4 App Domain: AutoLog.exe ProcessId: 4200 Process Name: D:\Codes\Enterprise Library\Enterprise Library Demos\PIAB\Demo\AutoLog\bin\Debug\AutoLog.exe Thread Name: Win32 ThreadId:4000 Extended Properties: ---------------------------------------- ---------------------------------------- Timestamp: 2012/3/19 6:03:00 Message: Enter method ToString Category: General Priority: -1 EventId: 1 Severity: Information Title: Machine: PC4 App Domain: AutoLog.exe ProcessId: 4200 Process Name: D:\Codes\Enterprise Library\Enterprise Library Demos\PIAB\Demo\AutoLog\bin\Debug\AutoLog.exe Thread Name: Win32 ThreadId:4000 Extended Properties: ---------------------------------------- ---------------------------------------- Timestamp: 2012/3/19 6:03:00 Message: Exit method ToString, use 00:00:00.0001410. Category: General Priority: -1 EventId: 1 Severity: Information Title: Machine: PC4 App Domain: AutoLog.exe ProcessId: 4200 Process Name: D:\Codes\Enterprise Library\Enterprise Library Demos\PIAB\Demo\AutoLog\bin\Debug\AutoLog.exe Thread Name: Win32 ThreadId:4000 Extended Properties: ----------------------------------------

实现了自动化Log后，回过头来再看第5步，Employee继承了MarshalByRefObject，一般我们的业务类或数据访问类都有基类，那么我们就需要使用接口
这里我添加一个IEmployee接口，里面就Work方法（ToString是重写Object的）。

using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.Unity; namespace AutoLog { public interface IEmployee { void Work(); } public class Employee : IEmployee { public Employee() { //this.Name = "Lele"; } public string Name { get; set; } [AutoLogCallHandler()] public void Work() { Console.WriteLine("Now is {0},{1} is working hard!",DateTime.Now.ToShortTimeString(),Name); throw new Exception("Customer Exception"); } [AutoLogCallHandler()] public override string ToString() { return string.Format("I'm {0}.",Name); } } }

然后在测试类改动一下

using System; using System.Collections.Generic; using System.Linq; using System.Text; using Microsoft.Practices.EnterpriseLibrary.PolicyInjection; using Microsoft.Practices.Unity; using Microsoft.Practices.EnterpriseLibrary.Logging; using Microsoft.Practices.EnterpriseLibrary.Common.Configuration; namespace AutoLog { class Program { private static LogWriter logWriter = EnterpriseLibraryContainer.Current.GetInstance(); static void Main(string[] args) { IEmployee emp = PolicyInjection.Create(); emp.Work(); Console.WriteLine(emp); } } }