Castle IOC容器实践之FactorySupport Facility

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Castle IOC容器实践之FactorySupport Facility

摘要：FactorySupport Facility允许我们使用已经存在的工厂来创建组件的实例，可以把已经存在的对象模型加入到容器中，以便它能够使用自动装配。它使用了以下两种处理策略：

1．使用访问器来访问组件的实例

2．使用静态方法或者实例方式来访问组件的实例

主要内容

1．概述

2．为什么需要FactorySupport Facility

3．如何使用

4．常见的配置示例

5．实现原理浅析

一．概述

FactorySupport Facility允许我们使用已经存在的工厂来创建组件的实例，可以把已经存在的对象模型加入到容器中，以便它能够使用自动装配。它使用了以下两种处理策略：

1．通过访问器来访问组件的实例

2．通过静态方法或者实例方式来访问组件的实例

二．为什么需要FactorySupport Facility

为了回答这个问题，我们先来看一个简单的使用工厂的例子，如下代码所示：

public interface IComponent

{
    void Display();
}

public class MyComponent : IComponent

{
    public MyComponent()

    {

    }

    public void Display()

    {
        Console.WriteLine("MyComponent");
    }
}

public class MyFactory

{
    public MyFactory()

    {

    }

    public IComponent Create()

    {
        return new MyComponent();
    }
}

现在要在程序中使用MyComponent的实例，简单一点会这样去写：

public class App

{
    static void Main()

    {
        MyFactory factory = new MyFactory();

        IComponent comp = factory.Create();

        comp.Display();

    }
}

正如你所看到的，在程序中使用new关键字创建了一个工厂的实例，再由工厂得到组件的实例。现在我们看使用FactorySupport Facility后带来了什么好处。工厂和组件的代码不变，仍然是：

public interface IComponent

{
    void Display();
}

public class MyComponent : IComponent

{
    public MyComponent()

    {

    }

    public void Display()

    {
        Console.WriteLine("MyComponent");
    }
}

public class MyFactory

{
    public MyFactory()

    {

    }

    public IComponent Create()

    {
        return new MyComponent();
    }
}

配置文件，现在你可以不用理解怎么去配置，后面会讲到。

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

<configuration>

    <facilities>

        <facility id="factorysupport" type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel" />

    </facilities>

    <components>

        <component id="myfactory" type="FactorySupportDemo.MyFactory,FactorySupportDemo" />

        <component id="mycomp" type="FactorySupportDemo.MyComponent,FactorySupportDemo"

            factoryId="myfactory" factoryCreate="Create"></component>

    </components>

</configuration>

使用组件的实例

public class App

{
    static void Main()

    {
        IWindsorContainer container = new WindsorContainer("../../Basic.xml");

        IComponent instance = (IComponent) container["mycomp"];

        instance.Display();

    }
}

看到了吗？我们并没有使用new关键字创建任何对象，只是把工厂、组件等通过配置文件抛给了IOC容器，再从容器中往外取的时候，就可以直接取到组件的实例，这些实例是由工厂自动创建的，这正是FactorySupport Facility的作用。

三．如何使用

知道了为什么需要FactorySupport Facility之后，下面就来看如何使用Facility。在前面的代码中大家都已经看到了，使用FactorySupport Facility是非常的简单。

1．加入FactorySupport Facility到容器中，可以使用代码加入也可以使用配置文件。

使用代码加入：

IWindsorContainer container = new WindsorContainer("../../Basic.xml");

container.AddFacility("factorysupport",new Castle.Facilities.FactorySupport.FactorySupportFacility());

使用配置文件：

<facilities>

    <facility id="factorysupport" type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel" />

</facilities>

2．加入组件时指定使用的是哪种方式

如果使用访问器只需要指定访问器的名称就可以了：

<component id="accessor.comp"

    type="Castle.Facilities.FactorySupport.Tests.Components.SingletonWithAccessor, Castle.Facilities.FactorySupport.Tests"

    instance-accessor="Instance">

</component>

如果使用工厂方法，需要指定工厂ID和工厂方法：

<component id="mycomp"

            type="Castle.Facilities.FactorySupport.Tests.Components.MyComp, Castle.Facilities.FactorySupport.Tests"

            factoryId="mycompfactory" factoryCreate="Create">

</component>

四．常见的配置示例

这是一些常见的配置示例，来自于Castle自带的测试代码中。

1．访问器配置示例

有这样一个单件类

public class SingletonWithAccessor

{
    private static readonly SingletonWithAccessor instance = new SingletonWithAccessor();

    private SingletonWithAccessor()

    {

    }

    public static SingletonWithAccessor Instance

    {
        get { return instance; }
    }
}

配置文件如下：

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

<configuration>

    <facilities>

        <facility id="factorysupport" type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel" />

    </facilities>

    <components>

        <component id="accessor.comp" type="Castle.Facilities.FactorySupport.Tests.Components.SingletonWithAccessor, Castle.Facilities.FactorySupport.Tests"

            instance-accessor="Instance"></component>

    </components>

</configuration>

2．普通工厂配置示例

组件类和工厂类如下

public class MyComp

{
    public MyComp()

    {

    }
}

public class MyCompFactory

{
    public MyComp Create()

    {
        return new MyComp();
    }
}

配置文件如下：

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

<configuration>

    <facilities>

        <facility id="factorysupport" type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel" />

    </facilities>

    <components>

        <component id="mycompfactory" type="Castle.Facilities.FactorySupport.Tests.Components.MyCompFactory, Castle.Facilities.FactorySupport.Tests" />

        <component id="mycomp" type="Castle.Facilities.FactorySupport.Tests.Components.MyComp, Castle.Facilities.FactorySupport.Tests"

            factoryId="mycompfactory" factoryCreate="Create"></component>

    </components>

</configuration>

3．带参工厂配置示例

组件类和工厂类如下：

public class MyComp

{
    private string storeName;

    private IDictionary props;

    internal MyComp()
    {

    }

    internal MyComp(String storeName, IDictionary props)

    {
        this.storeName = storeName;

        this.props = props;
    }

    public string StoreName

    {
        get { return storeName; }
    }

    public IDictionary Props

    {
        get { return props; }
    }
}

public class MyCompFactory2

{
    public MyCompFactory2()

    {

    }

    public MyComp Create(String storeName, IDictionary props)

    {
        return new MyComp(storeName, props);
    }
}

配置文件如下：

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

<configuration>

    <facilities>

        <facility id="factorysupport" type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel" />

    </facilities>

    <components>

       <component id="mycompfactory" type="Castle.Facilities.FactorySupport.Tests.Components.MyCompFactory2, Castle.Facilities.FactorySupport.Tests"></component>

        <component id="mycomp" type="Castle.Facilities.FactorySupport.Tests.Components.MyComp, Castle.Facilities.FactorySupport.Tests"

            factoryId="mycompfactory" factoryCreate="Create">

            <parameters>

                <storeName>MyStore</storeName>

                <props>

                    <dictionary>

                        <entry key="key1">item1</entry>

                        <entry key="key2">item2</entry>

                    </dictionary>

                </props>

            </parameters>

        </component>

    </components>

</configuration>

4．使用自动装配工厂配置示例

组件类和工厂类如下：

public interface IMyService

{

}

public class MyComp

{
    private IMyService serv;

    internal MyComp()

    {

    }

    internal MyComp(IMyService serv)

    {
        this.serv = serv;
    }

    public IMyService Service

    {
        get { return serv; }
    }
}

public class MyCompFactory3

{
    public MyCompFactory3()

    {

    }

    public MyComp Create(IMyService serv)

    {
        return new MyComp(serv);
    }
}

配置文件如下：

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

<configuration>

    <facilities>

        <facility id="factorysupport" type="Castle.Facilities.FactorySupport.FactorySupportFacility, Castle.MicroKernel" />

    </facilities>

    <components>

        <component id="myserv" service="Castle.Facilities.FactorySupport.Tests.Components.IMyService, Castle.Facilities.FactorySupport.Tests"

            type="Castle.Facilities.FactorySupport.Tests.Components.DefaultMyService, Castle.Facilities.FactorySupport.Tests" />

       <component id="mycompfactory" type="Castle.Facilities.FactorySupport.Tests.Components.MyCompFactory3, Castle.Facilities.FactorySupport.Tests"></component>

        <component id="mycomp" type="Castle.Facilities.FactorySupport.Tests.Components.MyComp, Castle.Facilities.FactorySupport.Tests"

            factoryId="mycompfactory" factoryCreate="Create">

            </component>

    </components>

</configuration>

五．实现原理浅析

FactorySupport Facility的实现也是非常的简单，主要是通过两个ComponentActivator来实现，分别为AccessorActivator和FactoryActivator，根据配置文件的不同调用不同的Activator。

String instanceAccessor = model.Configuration.Attributes["instance-accessor"];

String factoryId = model.Configuration.Attributes["factoryId"];

String factoryCreate = model.Configuration.Attributes["factoryCreate"];

if (instanceAccessor != null)

{

    model.ExtendedProperties.Add( "instance.accessor", instanceAccessor );

    model.CustomComponentActivator = typeof(AccessorActivator);

}

else if (factoryId != null)

{

    model.ExtendedProperties.Add( "factoryId", factoryId );

    model.ExtendedProperties.Add( "factoryCreate", factoryCreate );

    model.CustomComponentActivator = typeof(FactoryActivator);

}

好了，关于FactorySupport Facility就介绍到这儿，更多Castle的文章您可以访问《Castle 开发系列文章》。

PDF版本下载：/Files/Terrylee/FactorySupportFacility.rar

示例代码下载：/Files/Terrylee/FactorySupportDemo.rar

参考资料

Castle的官方网站http://www.castleproject.org

（出处：博客园http://terrylee.cnblogs.com）

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原文地址：https://www.cnblogs.com/Terrylee/p/castle_ioc_factorysupport_facility.html