Java.util.ServiceLoader.load() Method

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Description

The java.util.ServiceLoader.load(Class<S> service,ClassLoader loader) method Creates a new service loader for the given service type and class loader.

Declaration

Following is the declaration for java.util.ServiceLoader.load() method

public static <S> ServiceLoader<S> load(Class<S> service,ClassLoader loader)

Parameters

  • service -- The interface or abstract class representing the service

  • loader -- The class loader to be used to load provider-configuration files and provider classes, or null if the system class loader (or, failing that, the bootstrap class loader) is to be used

Return Value

This method returns a new service loader

Exception

  • NA

Example

In order the service to be registered, we need a META-INF/service folder in our classpath. In this particular folder, we need a text file with the name of the interface we implementing containing a single line listing the concrete class name of the implementation. In our case the name of the file is com.tutorialspoint.ServiceProvider and contains this line :

com.tutorialspoint.ServiceImplementation

Our service code is the following :

package com.tutorialspoint;

public class ServiceImplementation extends ServiceProvider {
    
    public String getMessage() {
        return "Hello World";
    }
}

The following code loads the service that is registered and uses it to get the message from the service:

package com.tutorialspoint;

import java.util.ServiceLoader;

public abstract class ServiceProvider {

   public static ServiceProvider getDefault() {

      // load our plugin with the default system class loader
      ServiceLoader<ServiceProvider> serviceLoader =
              ServiceLoader.load(ServiceProvider.class,
              ClassLoader.getSystemClassLoader());

      //checking if load was successful
      for (ServiceProvider provider : serviceLoader) {
         return provider;
      }
      throw new Error("Something is wrong with registering the addon");
   }

   public abstract String getMessage();

   public static void main(String[] ignored) {
      // create a new provider and call getMessage()
      ServiceProvider provider = ServiceProvider.getDefault();
      System.out.println(provider.getMessage());
   }
}

Let us compile and run the above program, this will produce the following result:

Hello World



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