public class CustomServiceLoader {

    public static final String MAPPING_CONFIG_PREFIX = "META-INF/services";

    public static <S> List<S> loade(Class<S> service) throws Exception{
        String mappingConfigFile = MAPPING_CONFIG_PREFIX + "/" + service.getName() ;
        //由于一个接口的实现类可能存在多个jar包中的META-INF目录下，所以下面使用getResources返回一个URL数组
        Enumeration<URL> configFileUrls =  CustomServiceLoader.class.getClassLoader().getResources(mappingConfigFile);
        if(configFileUrls == null){
            return null ;
        }
        List<S> services = new LinkedList<S>();
        while(configFileUrls.hasMoreElements()){
            URL configFileUrl = configFileUrls.nextElement();
            String configContent = IOUtils.toString(configFileUrl.openStream());
            String[] serviceNames = configContent.split("\n");
            for(String serviceName : serviceNames){
                Class serviceClass = CustomServiceLoader.class.getClassLoader().loadClass(serviceName);
                Object serviceInstance = serviceClass.newInstance();
                services.add((S)serviceInstance);
            }
        }
        return services ;
    }

}