package com.ctrip.framework.apollo.core.utils;

import java.util.Iterator;
import java.util.ServiceLoader;

public class ServiceBootstrap {
   public static <S> S loadFirst(Class<S> clazz) {
      Iterator<S> iterator = loadAll(clazz);
      if (!iterator.hasNext()) {
         throw new IllegalStateException(String.format(
            "No implementation defined in /META-INF/services/%s, please check whether the file exists and has the right implementation class!",
            clazz.getName()));
      }
      return iterator.next();
   }

   private static <S> Iterator<S> loadAll(Class<S> clazz) {
      ServiceLoader<S> loader = ServiceLoader.load(clazz);

      return loader.iterator();
   }
}
