Castle IOC 實踐：Startable Facility（一）使用篇

Facility 簡介

Startable Facility 讓組件在依賴關係滿足後自動啟動/停止。資訊：

實作 IStartable 介面（標準用法）

Program 控制 Server 啟停

public class Program : IStartable
{
    private Server _server;
    public Program(Server server) { this._server = server; }
    public void Start() { _server.Start(); }
    public void Stop() { _server.Stop(); }
}

Server 需 Host 與 Port

public class Server
{
    private string _host; private int _port;
    public Server(string host, int port) { _host = host; _port = port; }
    public void Start() { Console.WriteLine("Server {0}:{1} Start", _host, _port); Console.ReadLine(); }
    public void Stop() { Console.WriteLine("Server {0}:{1} Stop", _host, _port); Console.ReadLine(); }
}

Server 配置檔

<?xml version="1.0" encoding="utf-8"?>
<configuration>
  <components>
    <component id="server">
      <parameters><host>localhost</host><port>110</port></parameters>
    </component>
  </components>
</configuration>

注意：配置檔與 Startable Facility 無關，純屬 Castle IOC 普通配置。

客戶端程式

public class App
{
    public static void Main()
    {
        IWindsorContainer container = new WindsorContainer(new XmlInterpreter("../../BasicUsage.xml"));
        container.AddFacility("startable", new StartableFacility());
        container.AddComponent("program", typeof(Program)); // (A) 依賴未滿足，不啟動
        container.AddComponent("server", typeof(Server));   // (B) 依賴滿足，自動啟動
    }
}

執行到 (A) 時 Server 尚未註冊，依賴不滿足；執行 (B) 後依賴滿足，Program 自動啟動呼叫 Start()。

不實作 IStartable 的替代用法（易被忽略）

源碼揭示：除介面判斷外，若組件有 startable Attribute 也可自動啟動。

無介面組件

[Transient]
public class NoInterfaceStartableComponent
{
    private bool _Started = false, _Stopped = false;
    public void Start() { _Started = true; }
    public void Stop() { _Stopped = true; }
    public bool Started { get { return _Started; } }
    public bool Stopped { get { return _Stopped; } }
}

測試代碼（配置啟動）

[Test]
public void TestComponentWithNoInterface()
{
    IKernel kernel = new DefaultKernel();
    MutableConfiguration compNode = new MutableConfiguration("component");
    compNode.Attributes["id"] = "b";
    compNode.Attributes["startable"] = "true";
    compNode.Attributes["startMethod"] = "Start";
    compNode.Attributes["stopMethod"] = "Stop";
    kernel.ConfigurationStore.AddComponentConfiguration("b", compNode);
    kernel.AddFacility("startable", new StartableFacility());
    kernel.AddComponent("b", typeof(NoInterfaceStartableComponent));
    var component = kernel["b"] as NoInterfaceStartableComponent;
    Assert.IsNotNull(component);
    Assert.IsTrue(component.Started);
    Assert.IsFalse(component.Stopped);
    kernel.ReleaseComponent(component);
    Assert.IsTrue(component.Stopped);
}

可將 IKernel 換為 Castle.Windsor 使用。這提供了不實作介面也能享受自動生命週期管理的彈性。