类加载器：ServiceLoader简述

e();
}

（2）具体服务实现1：HDFSService

package com.impl;

import com.service.IService;

public class HDFSService implements IService {

    @Override

    public String sayHello() {

        return "Hello HDFSService";

    }

    @Override

    public String getScheme() {

        return "hdfs";

    }
}

（3） 具体服务实现2：LocalService

package com.impl;

import com.service.IService;

public class LocalService  implements IService {

    @Override

    public String sayHello() {

        return "Hello LocalService";

    }

    @Override

    public String getScheme() {

        return "local";

    }
}

（4）配置：META-INF/services/com.service.IService

com.impl.HDFSService
com.impl.LocalService

(5)测试类

package com.test;

import java.util.ServiceLoader;

import com.service.IService;

public class Test {

    public static void main(String[] args) {

        ServiceLoader serviceLoader  = ServiceLoader.load(IService.class);

        for (IService service : serviceLoader) {

            System.out.println(service.getScheme()+"="+service.sayHello());

        }

    }
}

结果：

hdfs=Hello HDFSService
local=Hello LocalService

可以看到ServiceLoader可以根据IService把定义的两个实现类找出来，返回一个ServiceLoader的实现，而ServiceLoader实现了Iterable接口，所以可以通过ServiceLoader来遍历所有在配置文件中定义的类的实例