Enterprise Library Policy Injection Application Block 之三:PIAB的扩展—创建自定义CallHandler(提供Source Code下载)

本系列的第一部分PIAB使用场景进行了简单的介绍,作中阐述了通过PIPolicy Injection)的方式实现了Business LogicNon-Business Infrastructure Logic的分离,从而实现了AOPAspect Oriented Programming)。在第二部分中详细介绍PIAB的实现机制:通过自定义RealProxy的方式实现了Method Injection。通过这几天接收到的网友的留言,觉得很多人对在具体的项目开发中如何使用PIAB还有很多困惑,对PIAB的价值还不是很了解。为此,在本系列的第三篇文章中,我将以Walk through的方式定义一个Custom CallHandler,并通过两种不同的方式:AttributeConfiguration将其运用到所以得Method上。你可以这里从下载Source Code.

场景描述:本Demo模拟一个简单的场景:订单处理,我们将订单处理之前对订单的验证通过PI的方式提供。我们假设需要进行如何的验证:

  • Order Date必须早于当前日期。
  • 必须有具体的Product
  • 供应商必须是制定的几家合法供应商(可选)。
  • Order的总价必须是所有Product价格之和(可选)。

其中前两个验证规则为必须的,后两个未可选项,可以通过AttributeConfiguration进行相应的配置。

步骤一、创建解决方案和项目

如下图,整个Solution由两个Project组成,一个Class Library和一个Console Application。所有与Custom CallHandlerClass都定义在Artech.CustomCallHandler.ClassLibrary中,而Artech.CustomCallHandler.ConsoleApp重在演示对Custom CallHandler的使用。


Artech.CustomCallHandler.ClassLibrary中,添加如下3Dll Reference,你可以在安装Enterprise Library V3 .1的目录中找到。

  • Microsoft.Practices.EnterpriseLibrary.Common
  • Microsoft.Practices.EnterpriseLibrary.PolicyInjection
  • Microsoft.Practices.ObjectBuilder

步骤二、定义辅助类:OrderOrderItemOrderValidationException

   1: namespace Artech.CustomCallHandlers
   2: {
   3:     public class Order
   4:     {
   5:         public Order()
   6:         {
   7:             this.Items = new List<OrderItem>();
   8:         }
   9:         public Guid OrderNo{ get; set; }
  10:         public DateTime OrderDate{ get; set; }
  11:         public string Supplier{ get; set; }
  12:         public IList<OrderItem> Items{ get; set; }
  13:         public double TotalPrice{ get; set; }
  14:     }
  15: }
   1: namespace Artech.CustomCallHandlers
   2: {
   3:     public class OrderItem
   4:     {
   5:         public Guid ProductID{ get; set; }
   6:         public string ProductName{ get; set; }
   7:         public double UnitPrice{ get; set; }
   8:         public int Quantity{ get; set; }
   9:     }
  10: }
   1: [Serializable]
   2: public class OrderValidationException : Exception
   3: {
   4:     public OrderValidationException() { }
   5:     public OrderValidationException(string message) : base(message) { }
   6:     public OrderValidationException(string message, Exception inner) : base(message, inner) { }
   7:     protected OrderValidationException(
   8:       System.Runtime.Serialization.SerializationInfo info,
   9:       System.Runtime.Serialization.StreamingContext context)
  10:         : base(info, context) { }
  11: }

步骤三、定义Custom CallHandler:  OrderValidationCallHandler

   1: namespace Artech.CustomCallHandlers
   2: {
   3:     public class OrderValidationCallHandler : ICallHandler
   4:     {
   5:         private static IList<string> _legalSuppliers;
   6:         public static IList<string> LegalSuppliers
   7:         {
   8:             get
   9:             {
  10:                 if (_legalSuppliers == null)
  11:                 {
  12:                     _legalSuppliers = new List<string>();
  13:                     _legalSuppliers.Add("Company AAA");
  14:                     _legalSuppliers.Add("Company BBB");
  15:                     _legalSuppliers.Add("Company CCC");
  16:                 }
  17:  
  18:                 return _legalSuppliers;
  19:             }
  20:         }
  21:         public bool ValidateTotalPrice{ get; set; }
  22:         public bool ValidateSupplier{ get; set; }
  23:         public IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext)
  24:         {
  25:             if (input.Inputs.Count == 0){return getNext()(input, getNext);}
  26:             Order order = input.Inputs[0] as Order;
  27:             if (order == null){return getNext()(input, getNext);}
  28:             if (order.OrderDate > DateTime.Today)
  29:             {
  30:                 return input.CreateExceptionMethodReturn(new OrderValidationException("The order date is later than the current date!"));
  31:             }
  32:  
  33:             if (order.Items.Count == 0)
  34:             {
  35:                 return input.CreateExceptionMethodReturn(new OrderValidationException("There are not any items for the order!"));
  36:             }
  37:  
  38:             if (this.ValidateSupplier)
  39:             {
  40:                 if (!LegalSuppliers.Contains<string>(order.Supplier))
  41:                 {
  42:                     return input.CreateExceptionMethodReturn(new OrderValidationException("The supplier is inllegal!"));
  43:                 }
  44:             }
  45:  
  46:             if (this.ValidateTotalPrice)
  47:             {
  48:                 double totalPrice = 0;
  49:                 foreach (OrderItem item in order.Items)
  50:                 {
  51:                     totalPrice += item.Quantity * item.UnitPrice;
  52:                 }
  53:                 if (totalPrice != order.TotalPrice)
  54:                 {
  55:                     return input.CreateExceptionMethodReturn(new OrderValidationException("The sum of the order item is not equal to the order total price!"));
  56:                 }
  57:             }
  58:  
  59:             return getNext()(input, getNext);
  60:         }
  61:     }
  62: }

OrderValidationCallHandler实现了InterfaceMicrosoft.Practices.EnterpriseLibrary.PolicyInjection. ICallHandlerICallHandler仅仅有一个方法成员:

   1: namespace Microsoft.Practices.EnterpriseLibrary.PolicyInjection
   2: {
   3:     public interface ICallHandler
   4:     {
   5:         IMethodReturn Invoke(IMethodInvocation input, GetNextHandlerDelegate getNext);
   6:     }
   7: }
   8:  

参数input代表对方法的调用,你可以通过他们获得方法调用的参数、ContextMethodBaseTarget Object。上本系列的第二部分已经详细介绍了,运用到某一个Method上的Policy可能包含一个或多个CallHandler,这些Handler在初始化的时候串成一个Pipeline。在一般的情况下在完成某一个Handler的操作之后会调用后一个Handler或者是Target Object(如何改Handler是最后一个Handler)。但是在一些特殊的场合,比如:验证错误;在执行当前Handler的操作时抛出Exception;对于某些特殊的输入有固定的返回值,那么就没有必要再将接力棒向后传递了。在这个时候我们可能直接抛出Exception或者返回一个特设的返回值。这个时候可以调用CreateExceptionMethodReturnCreateMethodReturn来实现。

   1: namespace Microsoft.Practices.EnterpriseLibrary.PolicyInjection
   2: {
   3:     public interface IMethodInvocation
   4:     {
   5:         IParameterCollection Arguments { get; }
   6:         IParameterCollection Inputs { get; }
   7:         IDictionary InvocationContext { get; }
   8:         MethodBase MethodBase { get; }
   9:         object Target { get; }
  10:         IMethodReturn CreateExceptionMethodReturn(Exception ex);
  11:         IMethodReturn CreateMethodReturn(object returnValue, params object[] outputs);
  12:     }
  13: }

而第二个参数getNext是一个Delegate,代表对CallHandler Pipeline后面CallHandler或者是Target Object的调用,这也在第二部分有提到。

我们在回到Invoke的具体定义。我们假设我们具体调用的Method的第一个参数必须是我们定义的Order对象:先验证方法的调用是否含有输入参数(如何没有直接调用后面的CallHandler或者Target Object);返回获得第一个输入参数并验证其类型(如果不是Order类型直接调用后面的CallHandler或者Target Object

   1: if (input.Inputs.Count == 0)
   2: {
   3:     return getNext()(input, getNext);
   4: }
   5: Order order = input.Inputs[0] as Order;
   6: if (order == null)
   7: {
   8:     return getNext()(input, getNext);
   9: }

然后我们再验证Order对象是否满足我们在上面提出的验证规则,先看看必须的验证规则:对Order DateOrder Item Count的验证。

   1: if (order.OrderDate > DateTime.Today)
   2: { 
   3:    return input.CreateExceptionMethodReturn(new OrderValidationException("The order date is later than the current date!"));
   4: }
   5: if(order.Items.Count == 0)
   6: {
   7:    return input.CreateExceptionMethodReturn(new OrderValidationException("There are not any items for the order!"));
   8: }

以及对可选的规则的验证:Total PriceSupplier。是否需要对其进行验证由两个Property来决定: ValidateSupplierValidateTotalPrice

   1: if (this.ValidateSupplier)
   2: {
   3:     if (!LegalSuppliers.Contains<string>(order.Supplier))
   4:     {
   5:         return input.CreateExceptionMethodReturn(new OrderValidationException("The supplier is inlegal!"));
   6:     }
   7: }
   8:  
   9: if(this.ValidateTotalPrice)
  10: {
  11:     double totalPrice = 0;
  12:     foreach (OrderItem item in order.Items)
  13:     {
  14:         totalPrice += item.Quantity * item.UnitPrice;
  15:     }
  16:     if (totalPrice != order.TotalPrice)
  17:     {
  18:         return input.CreateExceptionMethodReturn(new OrderValidationException("The sum of product unit price * quantity is not equal to the order total price!"));
  19:     }
  20: }

最后将接力棒向后传递:

   1: return getNext()(input, getNext);

到此为止,我们的OrderValidationCallHandler就定义完毕。但这仅仅完成了一半而已。因为我们最终需要通过Attribute或者Configuration的方式将我们的CallHandler运用到具体的Method上。我们先来看看使用Attribute的清况。我们需要在定一个Custom Attribute: OrderValidationCallHandlerAttribute.

   1: namespace Artech.CustomCallHandlers
   2: {
   3:     [AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
   4:     public class OrderValidationCallHandlerAttribute : HandlerAttribute
   5:     {
   6:         public bool ValidateTotalPrice{ get; set; }
   7:         public bool ValidateSupplier{ get; set; }
   8:  
   9:         public override ICallHandler CreateHandler()
  10:         {
  11:             return new OrderValidationCallHandler() { ValidateSupplier = this.ValidateSupplier, ValidateTotalPrice = this.ValidateTotalPrice };
  12:         }
  13:     }
  14: }

这是一个派生Microsoft.Practices.EnterpriseLibrary.PolicyInjection. HandlerAttribute自得特殊的Custom AttributeHandlerAttribute是一个Abstract Class,继承自该Class通过其OrverrideCreateHandler来创建所需要的CallHandler,在这里当然是创建我们定义的OrderValidationCallHandler。由于对Total PriceSupplier的验证时可选的,所以我们定义了两个对应的Property来供Developer进行自由地配置,这两个Property用于初始化CallHandler

步骤四、通过Attribute运用OrderValidationCallHandler

我想到此为止,我们已经迫不及待地想将我们定义的OrderValidationCallHandler应用到我们程序中了。我们就通过一个Console Application来演示如何通过Attibute的方式来运用OrderValidationCallHandler到我们所需的Method 上。现在定义以一个处理OrderClass: OrderProcessor

   1: public class OrderProcessor : MarshalByRefObject
   2: {
   3:     [OrderValidationCallHandlerAttribute]
   4:     public void ProcessOrder(Order order)
   5:     {
   6:         Console.WriteLine("The order has been processed!");
   7:     }
   8:     public static Order CreateOrder(DateTime orderDate, string supplier)
   9:     {
  10:         Order order = new Order() { OrderNo = Guid.NewGuid(), OrderDate = orderDate, Supplier = supplier, TotalPrice = 10000 };
  11:         order.Items.Add(new OrderItem() { ProductID = Guid.NewGuid(), UnitPrice = 6000, Quantity = 1, ProductName = "PC" });
  12:         order.Items.Add(new OrderItem() { ProductID = Guid.NewGuid(), UnitPrice = 5000, Quantity = 2, ProductName = "Print" });
  13:         return order;
  14:     }
  15: }

CreateOrder用于创建Order对象。而我们将我们的OrderValidationCallHandlerAttribute运用到ProcessOrder Method上。现在我们就可以在Main方法上调用这个方法了:

   1: class Program
   2: {
   3:     static void Main(string[] args)
   4:     {
   5:         OrderProcessor orderProcessor = PolicyInjection.Create<OrderProcessor>();
   6:         Order order;
   7:         try
   8:         {
   9:             order = OrderProcessor.CreateOrder(DateTime.Today.AddDays(1), " Company AAA");
  10:             Console.WriteLine("Proceed to process an order with an invalid order date!");
  11:             orderProcessor.ProcessOrder(order);
  12:         }
  13:         catch (OrderValidationException ex)
  14:         {
  15:             Console.WriteLine("Error: {0}", ex.Message);
  16:         }
  17:         try
  18:         {
  19:             order = OrderProcessor.CreateOrder(DateTime.Today.AddDays(-1), " Company DDD");
  20:             Console.WriteLine("Proceed to process an order with an illegal supplier!");
  21:             orderProcessor.ProcessOrder(order);
  22:         }
  23:  
  24:         catch (OrderValidationException ex)
  25:         {
  26:             Console.WriteLine("Error: {0}", ex.Message);
  27:         }
  28:  
  29:         try
  30:         {
  31:             order = OrderProcessor.CreateOrder(DateTime.Today.AddDays(-1), " Company AAA");
  32:             Console.WriteLine("Proceed to process an order with incorrect total price!");
  33:             orderProcessor.ProcessOrder(order);
  34:         }
  35:         catch (OrderValidationException ex)
  36:         {
  37:             Console.WriteLine("Error: {0}", ex.Message);
  38:  
  39:         }
  40:     }
  41: }

下面试输出结果:


我们看出,
Order Date 的验证正常执行,而对于Total PriceSupplier的验证却没有起作用。因为这两个是可选的(默认为不进行验证),我们可以通过修改运用在ProcessOrder MethodOrderValidationCallHandlerAttribute来进行有效的配置。比如:

   1: [OrderValidationCallHandlerAttribute(ValidateSupplier = true, ValidateTotalPrice = true)]
   2: public void ProcessOrder(Order order)
   3: {
   4:      Console.WriteLine("The order has been processed!");
   5: }

这样将会出现如下的结果:


步骤五、 定义HandlerDataCallHandlerAssembler

在上面我们实现了通过Attribute的方式使用CallHandler的方式,我们现在来看看另一种运用CallHandler的方式:Configuration。为此我们需要定义两个额外的Class: HandlerDataCallHandlerAssembler。前者用于定义Configuration相关的Property,而后者则通过Configuration创建并初始化相应的CallHandler

下面是HandlerData的定义:

   1: namespace Artech.CustomCallHandlers
   2: {
   3:     [Assembler(typeof(OrderValidationCallHandlerAssembler))]
   4:     public class OrderValidationCallHandlerData : CallHandlerData
   5:     {
   6:         [ConfigurationProperty("validateSupplier", DefaultValue = false)]
   7:         public bool ValidateSupplier
   8:         {
   9:             get{return (bool)base["validateSupplier"];}
  10:             set{base["validateSupplier"] = value;}
  11:         }
  12:  
  13:         [ConfigurationProperty("validateTotalPrice", DefaultValue = false)]
  14:         public bool ValidateTotalPrice
  15:         {
  16:             get{return (bool)base["validateTotalPrice"];}
  17:             set{base["validateTotalPrice"] = value;}
  18:         }
  19:     }
  20: }

这和ConfigurationProperty相同,唯一的区别是在Class上运用了一个Assembler Attribute,并制定了一个CallHandlerAssembler typeOrderValidationCallHandlerAssemblerOrderValidationCallHandlerAssembler定义如下:

   1: namespace Artech.CustomCallHandlers
   2: {
   3:     public class OrderValidationCallHandlerAssembler : IAssembler<ICallHandler, CallHandlerData>
   4:     {
   5:         public ICallHandler Assemble(IBuilderContext context, CallHandlerData objectConfiguration, IConfigurationSource configurationSource, ConfigurationReflectionCache reflectionCache)
   6:         {
   7:             OrderValidationCallHandlerData handlerData = objectConfiguration as OrderValidationCallHandlerData;
   8:             return new OrderValidationCallHandler() { ValidateSupplier = handlerData.ValidateSupplier, ValidateTotalPrice = handlerData.ValidateTotalPrice };
   9:         }
  10:     }
  11: }

OrderValidationCallHandlerAssembler派生自IAssembler<ICallHandler, CallHandlerData>,实现了Assemble方法。该方法用于收集的Configuration来创建所需的CallHandler

到此为止,任务尚未结束,我们还需要将我们定义的CallHandlerHandlerData之间建立一个Mapping关系。这主要通过在CallHandler Class上运用ConfigurationElementType Attribute来实现。为此我们将此Attribute加在OrderValidationCallHandler上面:

   1: namespace Artech.CustomCallHandlers
   2: {
   3:    [ConfigurationElementType(typeof(OrderValidationCallHandlerData))]
   4:    public class OrderValidationCallHandler:ICallHandler
   5:     {
   6:         //...
   7:     }
   8: }

Step VI 通过Configuration来使用CallHandler

现在我们就可以采用Configuration的方式来讲我们定义的OrderValidationCallHandler运用到我们所需的Method上。我们先去掉OrderProcessor. ProcessOrder上的OrderValidationCallHandlerAttribute。然后添加一个Application Configuration 文件,并进行如下配置:

   1: <configuration>
   2:   <configSections>
   3:     <sectionname="policyInjection"type="Microsoft.Practices.EnterpriseLibrary.PolicyInjection.Configuration.PolicyInjectionSettings, Microsoft.Practices.EnterpriseLibrary.PolicyInjection, Version=3.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" />
   4:   </configSections>
   5:   <policyInjection>
   6:     <policies>
   7:       <addname="Policy">
   8:         <matchingRules>
   9:           <addtype="Microsoft.Practices.EnterpriseLibrary.PolicyInjection.MatchingRules.MemberNameMatchingRule, Microsoft.Practices.EnterpriseLibrary.PolicyInjection, Version=3.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" name="Member Name Matching Rule">
  10:             <matches>
  11:               <addmatch="ProcessOrder"ignoreCase="false" />
  12:             </matches>
  13:             </add>
  14:           </matchingRules>
  15:         <handlers>
  16:           <addtype="Artech.CustomCallHandlers.OrderValidationCallHandler, Artech.CustomCallHandlers"name="OrderValidationCallHandler"validateSupplier="true"validateTotalPrice="true"/>
  17:         </handlers>
  18:         </add>
  19:       </policies>
  20:   </policyInjection>
  21: </configuration>

policyInjection Configuration Section中添加了一个PolicyPolicy=Matching Rule + Call Handler, 对于Matching Rule,我们采用的是基于Method NameMicrosoft.Practices.EnterpriseLibrary.PolicyInjection.MatchingRules.MemberNameMatchingRule。而我们定义的OrderValidationCallHandler则加在<handlers> element下,两个属性validateSuppliervalidateTotalPrice直接置于其中。

我们再次运行我们的程序,我们的输出结果和上面的没有任何区别:

EnterLib PIAB系列:

Enterprise Library Policy Injection Application Block 之一: PIAB Overview
Enterprise Library Policy Injection Application Block 之二: PIAB设计和实现原理
Enterprise Library Policy Injection Application Block 之三: PIAB的扩展—创建自定义CallHandler(提供Source Code下载)
Enterprise Library Policy Injection Application Block 之四:如何控制CallHandler的执行顺序

posted @ 2008-02-19 09:15  Artech  阅读(10185)  评论(40编辑  收藏  举报