[item1]服务提供者接口

    静态工厂方法返回的对象所属的类，在编写包含该静态工厂方法的类时可以不必存在。这种灵活的静态工厂方法构成了服务提供者框架（Service Provider Framework）的基础，例如JDBC API。
     服务提供者框架中有三个重要的组件：服务接口（Sevice Interface）,这是提供者实现的；提供者注册API（provider Registration API）,这是系统用来注册实现的；服务访问API，是客户端用来获取服务的实例。
JDBC源代码学习之服务提供者框架
http://edwinljg.iteye.com/blog/565742

package chapter2;

/*
 * 服务接口。<BR> 
 */
public interface Service {
	public String read();
	public void write(String content);
}

package chapter2;

/*
 * 服务提供者接口。<BR>  
 */
public interface Provider {
	public Service getService();   
}

package chapter2;

/*
 * 服务提供者实现。<BR>  
 */
public class AdobeProvider implements Provider {
	
	static {
		ServiceManager.registerProvider("Adobe", new AdobeProvider());
		System.out.println("12313");
	}
	
	public Service getService() {
		return new ServiceImpl();
	}
	
	class ServiceImpl implements Service {
		
		public String read(){
			System.out.println("Adobe read...");
			return "";
		}
		
		public void write(String content) {
			System.out.println("Adobe write...");
		}
		
	}
	
}

package chapter2;

import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

/**
 * 服务管理类。<BR>
 */
public class ServiceManager {

	private ServiceManager() {
	}

	private static final Map<String, Provider> providers = 
		new ConcurrentHashMap<String, Provider>();

	public static void registerProvider(String name, Provider p) {
		providers.put(name, p);
	}
	
	public static Service getService(String name) {
		
		Provider p = providers.get(name);
		
		if(p == null) {
			throw new IllegalArgumentException("No provider registered with name:" + name);
		}
		
		return p.getService();
		
	}
	
}

package chapter2;

/**
 * 测试用类。<BR>
 */
public class Test {
	
	public static void main(String []args) throws Exception {
		//註冊服务
		Class.forName("chapter2.AdobeProvider");
	
		//Class.forName("MicrosoftProvider");
		//Class.forName("MacProvider");
		
		//获得服务
		Service service = ServiceManager.getService("Adobe");
		//Service service = ServiceManager.getService("Microsoft");
		//Service service = ServiceManager.getService("Mac");
		
		service.read();
		service.write("title");
		
	}
	
}

   对于JDBC来说，Connction就是它的服务访问接口，DriverManagers是提供者注册ApI,DriverManager.getConnetion是服务访问API.Driver就是服务提供者接口。