服务提供者框架模式

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public class Services {
    private Services(){}

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

    public static final String DEFAULT_PROVIDER_NAME = "<def>";

    //provider register Api 提供者注册API，系统用来注册实现，让客户端访问它们的
    public static void registerDefaultProvider(Provider p){
        registerProvider(DEFAULT_PROVIDER_NAME,p);
    }

    public static void registerProvider(String name,Provider p){
        providers.put(name,p);
    }

    public static Service newInstance(){
        return newInstance(DEFAULT_PROVIDER_NAME);
    }
    //service access api 客户端用来获取服务的实例的
    public static Service newInstance(String name){
        Provider p = providers.get(name);
        if (p == null){
            throw new IllegalArgumentException("No provider registered with name:"+name);//IllegalArgumentException此异常表明向方法传递了一个不合法或不正确的参数
        }
        return p.newService();
    }
}

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//服务接口：提供者实现
interface Service{
//    ...
}

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//提供者负责创建其服务实现的实例
interface Provider{
    Service newService();
}