The created API module with the name com.packt.service.api  contains a NotificationService interface to send notification and load service providers. To make this interface a service provider interface (SPI), we have to mention the 'use' clause in module-info.java. Our module code will be as follows:

NotificationService.java

package com.packt.service.api;

import java.util.ArrayList;
import java.util.List;
import java.util.ServiceLoader;

public interface NotificationService {
  
  /* Loads all the service providers */
  public static List<NotificationService> getInstances() {
    ServiceLoader<NotificationService> services = ServiceLoader.load(NotificationService.class);
    List<NotificationService> list = new ArrayList<>();
    services.iterator().forEachRemaining(list::add);
    return list;
  }
  
  /* Send notification with provided message and recipient */
  boolean sendNotification(String message, String recipient);
  
}

module-info.java will be as follows:

module com.packt.service.api {
  exports com.packt.service.api;
  uses com.packt.service.api.NotificationService;
}

The following  are the command line steps that need to be followed for the com.packt.service.api module jar. Assume that there will be an out directory in the com.packt.service.api module: