Dynamically loading plugin jars using ServiceLoader

Question

I\'m trying to create a plugin system for my application, and I want to start with something simple. Every plugin should be packed in a .jar file and implement the Sim

Answer 1

Starting from Java 9 the service providing scanning will be much easier and efficient. No more need for META-INF/services.

In the interface module declaration declare:

uses com.foo.spi.Service;

And in the provider's module:

provides com.foo.spi.Service with com.bar.ServiceImplementation

Answer 2

The problem was very simple. And stupid. In the plugin .jar files the /services/plugintest.SimplePlugin file was missing inside the META-INF directory, so the ServiceLoader couldn't identify the jars as services and load the class.

That's pretty much all, the second (and cleaner) way works like a charm.

Answer 3

The solution for your application concept has been already described in Oracle Documentation (including dynamically loading JARs)

Creating Extensible Applications With the Java Platform http://www.oracle.com/technetwork/articles/javase/extensible-137159.html

on the bottom of the article you will find links to

• source code of the example
• Javadoc ServiceLoader API

In my opinion it is better to slightly modify Oracle's example than reinventing the wheel as Omer Schleifer said.