用Bridge模式重写了Libvirt框架

前一个项目我们引用了开源软件Libvirt，Libvirt的实现非常不错，可以支持很多的Hypervisor。这两天再把设计模式翻出来看看，发现原来Libvirt是使用了Bridge设计模式，和Service Provider模式还有一定的区别，特用Java提供了框架如下：

Connect.java:这个类在Bridge模式中没有对应概念

package com.cisco.gendwang;

public class Connect 
{
}

Driver.java:这个类在Bridge模式中相当于Implementator

package com.cisco.gendwang;

public interface Driver 
{
	Connect open(String url);
	String getHostName(Connect conn);
	void close(Connect conn);
}

EsxiDriver.java:这个类在Bridge模式中相当于ConcreteImplementator1

package com.cisco.gendwang;

public class EsxiDriver implements Driver 
{
	public EsxiDriver()
	{
		System.out.println("ESXi driver is loaded");
	}
	
	public Connect open(String url)
	{
		System.out.println("Get an ESXi connection");
		return new Connect();
	}
	
	public String getHostName(Connect conn)
	{
		System.out.println("Host Name: CRDC-21");
		return "CRDC-21";
	}
	
	public void close(Connect conn)
	{
		System.out.println("Close an ESXi connection");
	}
}

XenDriver.java:这个类在Bridge模式中相当于ConcreteImplementator2

package com.cisco.gendwang;

public class XenDriver implements Driver 
{
	public XenDriver()
	{
		System.out.println("XEN driver is loaded");
	}
	
	public Connect open(String url)
	{
		System.out.println("Get an XEN connection");
		return new Connect();
	}
	
	public String getHostName(Connect conn)
	{
		System.out.println("Host Name: CRDC-90");
		return "CRDC-90";
	}
	
	public void close(Connect conn)
	{
		System.out.println("Close an XEN connection");
	}
}

Libvirt.java:这个类在Bridge中相当于Abstraction

package com.cisco.gendwang;

import java.util.HashMap;
import java.util.Map;

public class Libvirt 
{
	private Driver driver;
	private static final Map<String, Driver> drivers = new HashMap<String, Driver>();
	
	public static void registerDriver(String driverName, Driver driver)
	{
		drivers.put(driverName.toLowerCase(), driver);
	}
	
	public Connect virConnectOpen(String url)
	{
		int colonIndex = url.indexOf(":");
		if(colonIndex == -1)
		{
			return null;
		}
		
		String prefix = url.substring(0, colonIndex);
		
		driver = drivers.get(prefix.toLowerCase());
		
		return driver.open(url);
	}
	
	public String virGetHostName(Connect conn)
	{
		return driver.getHostName(conn);
	}
	
	public void virConnectClose(Connect conn)
	{
		driver.close(conn);
	}
}

Application.java: 这个类在Bridge中是Client

package com.cisco.gendwang;

public class Application 
{
	public static void main(String[] args)
	{
		Libvirt.registerDriver("ESXi", new EsxiDriver());
		Libvirt.registerDriver("XEN", new XenDriver());
		
		Libvirt libvirt1 = new Libvirt();
		Connect conn1 = libvirt1.virConnectOpen("xen://10.74.125.90");
		libvirt1.virGetHostName(conn1);
		libvirt1.virConnectClose(conn1);
		
		Libvirt libvirt2 = new Libvirt();
		Connect conn2 = libvirt2.virConnectOpen("esxi://10.74.125.21");
		libvirt2.virGetHostName(conn2);
		libvirt2.virConnectClose(conn2);
	}
}