Java的SPI机制实例详解

java.util.Comparator。
--META-INF
 --services
  --java.util.Comparator

com.company1.ComparatorProvider

package com.company1;
import java.util.Comparator;
import com.mycompany.myapp.MyItem;
public class ComparatorProvider implements Comparator<MyItem>{
  @Override
  public int compare(MyItem o1, MyItem o2) {
        //依据name排序 
    return o1.getName().compareTo(o2.getName());
  }
}

  //从class path中所有Jar的META-INF目录中搜索，找到合适的类并加载。
  private static ServiceLoader<Comparator> serviceLoader
  = ServiceLoader.load(Comparator.class);
  
  public static void main(String[] args)
  {
    List<MyItem> myList = new ArrayList<MyItem>();
    myList.add(new MyItem(2,"c","hhh"));
    myList.add(new MyItem(3,"k","ooo"));
    myList.add(new MyItem(4,"d","ppp"));
    myList.add(new MyItem(5,"b","ggg"));
    
    showList(myList);
    
    Collections.sort(myList,getCompartor());
    
    showList(myList);  
  }
  
  @SuppressWarnings("unchecked")
  private static Comparator<MyItem> getCompartor() {
    
    for(Comparator service : serviceLoader)
    {
      return (Comparator<MyItem>)service;
    }
        
    return null;
  }