Object Builder Application Block (4)

八、ObjectBuilder实务

8-1、ObjectBuilderWithConfiguration

截至目前为止，本文一直以程序方式来配置ObjectBuidler建立对象所需的各种对象，但在实务上，这些动作应该是交由配置文件来负责，这样才能在不重新编译应用程序的情况下，改变其行为或增加其功能。很幸运的，Microsoft于ObjectBuilder的范例中提供了一个途径来达到此目的，该范例定义了一个.xsd文件，其内定义了ConstructorInjection、SetterInjection、Singleton、TypeMapping所需要的schema，当然！这个xsd中也定义了Strategy的schema，允许设计者通过配置文件来添加对象建立时所需使用的Strategys。

ConsturctorInjectionWithConfiguration

我将Microsoft所提供可配置ObjectBuidler的范例中关于处理配置文件时的.xsd及相关文件提取出来，并添加MethodInjection时所需要的schema及程序代码，放置于本文的范例程序档中，当读者们需要使用配置文件这个功能时，可以将Config目录中的ObjectBuilderXmlConfig.xsd、ObjectBuilderXmlConfig.xsx、ObjectBuilderXmlConfig.cs、ObjectBuilderXmlConfig.Generate.cs等文件复制到项目目录中，并将ObjectBuilderXmlConfig.xsd、ObjectBuilderXmlConfig.Generate.cs加入到项目中，完成后再将ObjectBuilderXmlConfig.xsd设置成EmbeddedResource，如图10所示。

图10



接着将修改ObjectBuilderXmlConfig.cs中关于由Resource中取得.xsd内容的程序代码，修正namespace为项目的默认namespace即可。

程序44

private static ObjectBuilderXmlConfig ParseXmlConfiguration(string config)

{

XmlSerializer ser = new XmlSerializer(typeof(ObjectBuilderXmlConfig));

StringReader stringReader = new StringReader(config);

XmlSchema schema = XmlSchema.Read(Assembly.GetExecutingAssembly().GetManifestResourceStream(

"OB_CSConfigurationTest.ObjectBuilderXmlConfig.xsd"), null);

XmlReaderSettings settings = new XmlReaderSettings();

settings.ValidationType = ValidationType.Schema;

settings.Schemas.Add(schema);

XmlReader reader = XmlReader.Create(stringReader, settings);

ObjectBuilderXmlConfig configData = (ObjectBuilderXmlConfig)ser.Deserialize(reader);

return configData;

}

要使用配置文件来完成ConstructorInjection，我们必须在项目中新增一个xml文件，内容如下所示。

<?xml version="1.0" encoding="utf-8"?>

<object-builder-config xmlns="pag-object-builder" >

<build-rules >

<build-rule type="OB_ConfigurationTest.InputAccept,OB_CSConfigurationTest" mode="Instance" >

<constructor-params >

<ref-param type="OB_ConfigurationTest.PromptDataProcessor,OB_CSConfigurationTest" />

</constructor-params>

</build-rule>

</build-rules>

</object-builder-config>

在ObjectBuilderXmlConfig.xsd定义中，build-rules代表着此BuilderContext中所有的对象建立规则，每个build-rule对应着一个“类型/id”，类型格式为<type,Assembly>，id部份则可通过添加name这个attribute来设置，未指定时就以null为默认值，如下。

<?xml version="1.0" encoding="utf-8"?>

<object-builder-config xmlns="pag-object-builder" >

<build-rules >

<build-rule type="OB_ConfigurationTest.InputAccept,OB_CSConfigurationTest" name="id1" mode="Instance" >

......

每个build-rule可以拥有一个constructor-params区段，设计者可以在这个区段中添加value-param或是ref-param定义，前者是直接设置该参数的值，后者是通过reference方式来设值，本例中是将InputAccept构造函数的第一个参数值指定为PromptDataProcessor。程序45是使用这个配置文件的程序列表。

程序45

using System;

using System.Collections.Generic;

using System.Text;

using System.IO;

using System.Configuration;

using Microsoft.Practices.ObjectBuilder;

using Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ObjectBuilder;

using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;

namespace OB_ConfigurationTest

{

class Program

{

static void Main(string[] args)

{

using (FileStream fs = new FileStream("XmlFile1.xml", FileMode.Open, FileAccess.Read))

{

using (StreamReader sr = new StreamReader(fs))

{

Builder builder = new Builder(ObjectBuilderXmlConfig.FromXml(sr.ReadToEnd()));

InputAccept accept = builder.BuildUp<InputAccept>(new Locator(), null, null);

accept.Execute();

Console.Read();

}

}

}

}

public class InputAccept

{

private IDataProcessor _dataProcessor;

public void Execute()

{

Console.Write("Please Input some words:");

string input = Console.ReadLine();

input = _dataProcessor.ProcessData(input);

Console.WriteLine(input);

}

public InputAccept([Dependency(Name = "dataProcessor")]IDataProcessor dataProcessor)

{

_dataProcessor = dataProcessor;

}

}

public interface IDataProcessor

{

string ProcessData(string input);

}

public class DummyDataProcessor : IDataProcessor

{

#region IDataProcessor Members

public string ProcessData(string input)

{

return input;

}

#endregion

}

public class PromptDataProcessor : IDataProcessor

{

#region IDataProcessor Members

public string ProcessData(string input)

{

return "your input is:" + input;

}

#endregion

}

}

SetterInjectionWithConfiguration

同样的，我们也可以通过配置文件来完成SetterInjection，此范例所使用的配置文件如下。

<?xml version="1.0" encoding="utf-8"?>

<object-builder-config xmlns="pag-object-builder" >

<build-rules >

<build-rule type="OB_CSPropertyInjectionTest.InputAccept,OB_CSPropertyInjectionTest" mode="Instance" >

<property name="DataProcessor" >

<ref-param type="OB_CSPropertyInjectionTest.PromptDataProcessor,OB_CSPropertyInjectionTest" />

</property>

</build-rule>

</build-rules>

</object-builder-config>

设计者必须将要设置的属性定义放置于build-rule区段中的property，property有一个nameattribute，代表着欲设置属性的名称，如要设置一个以上的属性，只需添加多个property区段即可，程序46是使用此配置文件的程序代码。

程序46

using System;

using System.Collections.Generic;

using System.Text;

using System.IO;

using System.Configuration;

using Microsoft.Practices.ObjectBuilder;

using Microsoft.Practices.EnterpriseLibrary.Common.Configuration.ObjectBuilder;

using Microsoft.Practices.EnterpriseLibrary.Common.Configuration;

namespace OB_CSPropertyInjectionTest

{

class Program

{

static void Main(string[] args)

{

using (FileStream fs = new FileStream("XmlFile1.xml", FileMode.Open, FileAccess.Read))

{

using (StreamReader sr = new StreamReader(fs))

{

Builder builder = new Builder(ObjectBuilderXmlConfig.FromXml(sr.ReadToEnd()));

InputAccept accept = builder.BuildUp<InputAccept>(new Locator(), null, null);

accept.Execute();

Console.Read();

}

}

}

}

public class InputAccept

{

private IDataProcessor _dataProcessor;

[Dependency(Name = "DataProcessor")]

public IDataProcessor DataProcessor

{

get

{

return _dataProcessor;

}

set

{

_dataProcessor = value;

}

}

public void Execute()

{

Console.Write("Please Input some words:");

string input = Console.ReadLine();

input = _dataProcessor.ProcessData(input);

Console.WriteLine(input);

}

}

public interface IDataProcessor

{

string ProcessData(string input);

}

public class DummyDataProcessor : IDataProcessor

{

#region IDataProcessor Members

public string ProcessData(string input)

{

return input;

}

#endregion

}

public class PromptDataProcessor : IDataProcessor

{

#region IDataProcessor Members

public string ProcessData(string input)

{

return "your input is:" + input;

}

#endregion

}

}

MethodInjectionWithConfiguration

Microsoft所提供的配置文件机制并未定义MethodInjection的功能，我将其稍微修改来支持此功能，下面是MethodInjection时所用的配置文件。

<?xml version="1.0" encoding="utf-8"?>

<object-builder-config xmlns="pag-object-builder" >

<build-rules >

<build-rule type="OB_CSPropertyInjectionTest.InputAccept,OB_CSPropertyInjectionTest" mode="Instance" >

<property name="DataProcessor" >

<ref-param type="OB_CSPropertyInjectionTest.PromptDataProcessor,OB_CSPropertyInjectionTest" />

</property>

</build-rule>

</build-rules>

</object-builder-config>

用法与property大致相同，程序47是程序代码列表。

程序47

using System;

using System.Collections.Generic;

using System.Text;

using System.IO;

using Microsoft.Practices.ObjectBuilder;

namespace OB_CSMethodInjectionTest

{

class Program

{

static void Main(string[] args)

{

using (FileStream fs = new FileStream("XmlFile1.xml", FileMode.Open, FileAccess.Read))

{

using (StreamReader sr = new StreamReader(fs))

{

Builder builder = new Builder(ObjectBuilderXmlConfig.FromXml(sr.ReadToEnd()));

InputAccept accept = builder.BuildUp<InputAccept>(new Locator(), null, null);

accept.Execute();

Console.Read();

}

}

}

}

public class InputAccept

{

private IDataProcessor _dataProcessor;

public void SetDataProcessor([Dependency(Name = "dataProcessor")]IDataProcessor dataProcessor)

{

_dataProcessor = dataProcessor;

}

public void Execute()

{

Console.Write("Please Input some words:");

string input = Console.ReadLine();

input = _dataProcessor.ProcessData(input);

Console.WriteLine(input);

}

}

public interface IDataProcessor

{

string ProcessData(string input);

}

public class DummyDataProcessor : IDataProcessor

{

#region IDataProcessor Members

public string ProcessData(string input)

{

return input;

}

#endregion

}

public class PromptDataProcessor : IDataProcessor

{

#region IDataProcessor Members

public string ProcessData(string input)

{

return "your input is:" + input;

}

#endregion

}

}

SingletonWithConfiguration

通过配置文件，也可以定义那个“类型/id”的对象是使用Singleton模式，如下所示。

<build-rule type="OB_CSMethodInjectionTest.PromptDataProcessor,OB_CSMethodInjectionTest" mode="Singleton" />

TypeMappingWithConfiguration

我们也可以在配置文件中定义TypeMapping，如下所示。

<build-rule type="OB_CSMethodInjectionTest.IDataProcessor,OB_CSMethodInjectionTest" mode="Instance" >

<mapped-type type="OB_CSMethodInjectionTest.PromptDataProcessor,OB_CSMethodInjectionTest" />

</build-rule>

CustomizeStrategys

通过配置文件，也可以定义建立对象时所需要的Strategys，如下所示。

<object-builder-config xmlns="pag-object-builder" >

<strategies include-default="false" >

<strategy type="Microsoft.Practices.ObjectBuilder.TypeMappingStrategy,Microsoft.Practices.ObjectBuilder" />

<strategy type="Microsoft.Practices.ObjectBuilder.CreationStrategy,Microsoft.Practices.ObjectBuilder" />

<strategy type="Microsoft.Practices.ObjectBuilder.MethodExecutionStrategy,Microsoft.Practices.ObjectBuilder" />

.............

</strategies>

</object-builder-config>

include-default属性决定是否包含Builder对象所内建的Strategys。

九、后记

ObjectBuilder是一个相当不错的DependencyInjection实现对象，虽然相对于Spring、Avalon，ObjectBuilder并不是相当的完整，例如没有完整的配置文件驱动特色，但它所具备的高度延展性，可以让我们轻易的达到这个需求，且日后相信ObjectBuilder也会内建这些功能的。