SharpDevelop中Addin插件系统的详解(一)

王朝c#·作者佚名  2006-12-17
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SharpDevelop中Addin插件系统的详解(一)

SharpDevelop中Addin插件系统的详解(一) SharpDevelop中Addin插件系统的详解(一)

相信会有很多的Programmer们对换“插件”这一术语都会抱有很大的兴趣,而#SharpDevelopr中的插件系统正以它较大的灵活性、可扩展性吸引了从多Programmer的目光。

(关于#SharpDevelop源码,可以去http://sourceforge.com下载。)

1. 服务概念与Addin插件系统的结合

在剖析Addin插件系统之前,我们还是要首先来了解一下#SharpDevelop中的Service(服务)概念,这也正是基于#SharpDevelop的Addin插件系统与Service服务紧密结合所作出一种考虑。

在剖析Addin插件系统之前,我们还是要首先来了解一下#SharpDevelop中的Service(服务)概念,这也正是基于#SharpDevelop的Addin插件系统与Service服务紧密结合所作出一种考虑。

#SharpDevelop中的服务,是指用于提供一些诸如“OpenFile”功能的类。在#SharpDevelop中,为了保证这些服务类的可替换性、可扩展性以及服务类的简单定位功能,引入了用于管理这些服务类的ServiceManager类。由于该ServiceManager类采用了Singleton设计模式,从而保证了在#SharpDevelop的任一部分均可方便地获取、使用这些服务类。

以下为与服务概念相关的一些源码,读者可从SharpDevelop\src\Main\Core\Services、SharpDevelop\src\Main\Base\Services中获取。

////////////////////////////////////////////////////////////////////////////////////////////////////////////////

public class ServiceManager

{

ArrayList serviceList = new ArrayList();

Hashtable servicesHashtable = new Hashtable();

// Singleton design pattern.

static ServiceManager defaultServiceManager = new ServiceManager();

/// <summary>

/// Gets the default ServiceManager

/// </summary>

public static ServiceManager Services

{

Get { return defaultServiceManager; }

}

/// <summary>

/// Don't create ServiceManager objects, only have ONE per application.

/// </summary>

private ServiceManager()

{

// add 'core' services

AddService(new PropertyService());

AddService(new StringParserService());

AddService(new FileUtilityService());

}

/// <remarks>

/// This method initializes the service system to a path inside the add-in tree.

/// This method must be called ONCE.

/// </remarks>

public void InitializeServicesSubsystem(string servicesPath)

{

// add add-in tree services

AddServices((IService[])AddInTreeSingleton.AddInTree.GetTreeNodeservicesPath).BuildChildItems(this).ToArray(typeof(IService)));

// initialize all services

foreach (IService service in serviceList)

{

DateTime now = DateTime.Now;

service.InitializeService();

}

}

/// <remarks>

/// Calls UnloadService on all services. This method must be called ONCE.

/// </remarks>

public void UnloadAllServices()

{

foreach (IService service in serviceList)

{

service.UnloadService();

}

}

public void AddService(IService service)

{

serviceList.Add(service);

}

public void AddServices(IService[] services)

{

foreach (IService service in services)

{

AddService(service);

}

}

// HACK: MONO BUGFIX

// this doesn't work on mono:serviceType.IsInstanceOfType(service)

bool IsInstanceOfType(Type type, IService service)

{

Type serviceType = service.GetType();

foreach (Type iface in serviceType.GetInterfaces())

{

if (iface == type)

{

return true;

}

}

while (serviceType != typeof(System.Object))

{

if (type == serviceType)

{

return true;

}

serviceType = serviceType.BaseType;

}

return false;

}

/// <remarks>

/// Requestes a specific service, may return null if this service is not found.

/// </remarks>

public IService GetService(Type serviceType)

{

IService s = (IService)servicesHashtable[serviceType];

if (s != null)

{

return s;

}

foreach (IService service in serviceList)

{

if (IsInstanceOfType(serviceType, service))

{

servicesHashtable[serviceType] = service;

return service;

}

}

return null;

}

}

///////////////////////////////////////////////////////////////////////////////////////////////////////////////

/// <summary>

/// This interface must be implemented by all services.

/// </summary>

public interface IService

{

/// <summary>

/// This method is called after the services are loaded.

/// </summary>

void InitializeService();

/// <summary>

/// This method is called before the service is unloaded.

/// </summary>

void UnloadService();

event EventHandler Initialize;

event EventHandler Unload;

}

////////////////////////////////////////////////////////////////////////////////////////////////////////////////

值得我们关注的代码行有:

值得我们关注的代码行有:

// add add-in tree services

AddServices((IService[])AddInTreeSingleton.AddInTree.GetTreeNode(servicesPath).BuildChildItems(this).ToArray(typeof(IService)));

该语句将从Addin插件树中获取所要加载的所有服务类,并将这些服务类初始化后加入到服务管理容器中。由于Addin插件树是根据一系列的*.Addin文件创建的,所以它具有很强的可替换性、可扩展性。

同时,通过ServiceManager类的Service GetService(Type serviceType)方法,可以很轻易地获取服务管理容器中的任意类型的服务类。

例如,要获取服务管理容器中的IMessageService类,可经以下语句获取:

IMessageService servicer = (IMessageService)ServiceManager.Services.GetService(typeof(IMessageService));

(未完待续)

(未完待续)

 
 
 
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