Démontration d'un système de plugin en Java avec deux styles : interface et annotation

SocleDemo.java

package com.mathieupauly.javacoursesamples.plugin;

import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class SocleDemo {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {
        List<Plugin> plugins = loadPlugins(Arrays.asList(args));
        init(plugins);
        list(plugins);
        shutdown(plugins);
    }

    private static List<Plugin> loadPlugins(List<String> pluginNames) throws ClassNotFoundException, NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException {
        List<Plugin> plugins = new ArrayList<>();
        for (String pluginName : pluginNames) {
            plugins.add(loadPlugin(pluginName));
        }
        return plugins;
    }

    private static Plugin loadPlugin(String pluginName) throws ClassNotFoundException, NoSuchMethodException, InstantiationException, IllegalAccessException, InvocationTargetException {
        Class<Plugin> pluginImpl = (Class<Plugin>) Class.forName(pluginName);
        Constructor<Plugin> constructor = pluginImpl.getConstructor();
        return constructor.newInstance();
    }

    private static void shutdown(List<Plugin> plugins) throws InvocationTargetException, IllegalAccessException {
        for (Plugin plugin : plugins) {
            Method[] declaredMethods = plugin.getClass().getDeclaredMethods();
            Method stopMethod = Arrays.stream(declaredMethods)
                    .filter(method -> method.getAnnotation(Stop.class) != null)
                    .findFirst()
                    .orElseThrow(() -> new RuntimeException("Plugin should define a stop method"));
            stopMethod.invoke(plugin);
        }
    }

    private static void init(List<Plugin> plugins) {
        for (Plugin plugin : plugins) {
            plugin.initialize();
        }
    }

    private static void list(List<Plugin> plugins) {
        for (Plugin plugin : plugins) {
            System.out.println(plugin.version());
        }
    }
}

interface Plugin {
    Object version();

    void initialize();
}

class PluginImpl implements Plugin {

    public PluginImpl() {
    }

    @Override
    public Object version() {
        return "1.0";
    }

    @Override
    public void initialize() {
        System.out.println("Plugin impl init...");
    }

    @Stop
    public void foo() {
        System.out.println("Plugin impl stop...");
    }
}

class PluginImpl2 implements Plugin {

    public PluginImpl2() {
    }

    @Override
    public Object version() {
        return "2.0";
    }

    @Override
    public void initialize() {
        System.out.println("Plugin impl2 init...");
    }

    @Stop
    public void bar() {
        System.out.println("Plugin impl2 stop...");
    }
}

@Retention(RetentionPolicy.RUNTIME)
@interface Stop {
}