ConcreteConfiguration.java

package com.kinggoesgaming.foundations.api.configuration.abstraction.concrete;

import com.kinggoesgaming.foundations.api.configuration.Configuration;
import ninja.leaping.configurate.ConfigurationNode;
import ninja.leaping.configurate.loader.ConfigurationLoader;

import java.io.IOException;
import java.nio.file.Path;

/**
 * Base template for all concrete configuration files.
 *
 * <p>
 *     This class narrows down the {@link Configuration} interface for use with configuration files that can be stored on disk.
 * </p>
 *
 * @param <N> The {@link ConfigurationNode} type.
 * @param <L> The {@link ConfigurationLoader} type.
 */
public abstract class ConcreteConfiguration<N extends ConfigurationNode, L extends ConfigurationLoader<N>> implements Configuration<N, L> {

    protected Path file;
    protected N node;
    protected L loader;
    protected Class<? extends ConcreteConfiguration<N, L>> clazz;
    protected String header = "";

    @Override
    public final void save() throws IOException {
        loader.save(node);
    }

    @Override
    public final N get() {
        return node;
    }

}

ConcreteHoconConfiguration

package com.kinggoesgaming.foundations.api.configuration.abstraction.concrete;

import com.kinggoesgaming.foundations.api.configuration.annotation.ConcreteConfigAsset;
import com.kinggoesgaming.foundations.api.configuration.annotation.OptionalConfigAsset;
import ninja.leaping.configurate.ConfigurationOptions;
import ninja.leaping.configurate.commented.CommentedConfigurationNode;
import ninja.leaping.configurate.hocon.HoconConfigurationLoader;
import org.spongepowered.api.Sponge;
import org.spongepowered.api.asset.Asset;
import org.spongepowered.api.plugin.PluginContainer;

import java.io.IOException;
import java.nio.file.Files;
import java.util.Optional;

/**
 * Base template for all concrete HOCON configuration files.
 *
 * <p>
 *     This class narrows down the {@link ConcreteConfiguration} for use with configuration files that can be stored on disk as HOCON.
 * </p>
 */
public abstract class ConcreteHoconConfiguration extends ConcreteConfiguration<CommentedConfigurationNode, HoconConfigurationLoader> {

    @Override
    public void load() throws IOException {
        if (!Files.exists(file)) {
            create();
            save();
            return;
        }
        upgrade();
        save();
    }

    private void create() throws IOException {
        Files.createFile(file);
        upgrade();

        if (clazz.isAnnotationPresent(OptionalConfigAsset.class)) {
            OptionalConfigAsset optionalConfigAsset = clazz.getAnnotation(OptionalConfigAsset.class);
            Optional<PluginContainer> pluginContainer = Sponge.getPluginManager().getPlugin(optionalConfigAsset.plugin());

            if (pluginContainer.isPresent()) {
                Optional<Asset> optionalAsset;
                HoconConfigurationLoader tempLoader;

                for (String asset : optionalConfigAsset.assets()) {
                    optionalAsset = pluginContainer.get().getAsset(asset);

                    if (optionalAsset.isPresent()) {
                        tempLoader = HoconConfigurationLoader.builder().setURL(optionalAsset.get().getUrl()).build();
                        node.mergeValuesFrom(tempLoader.load());
                    }
                }
            }
        }
    }

    private void upgrade() throws IOException {
        loader = HoconConfigurationLoader.builder().setPath(file).build();
        node = loader.load(ConfigurationOptions.defaults().setHeader(header));
        if (clazz.isAnnotationPresent(OptionalConfigAsset.class)) {
            ConcreteConfigAsset optionalConfigAsset = clazz.getAnnotation(ConcreteConfigAsset.class);
            Optional<PluginContainer> pluginContainer = Sponge.getPluginManager().getPlugin(optionalConfigAsset.plugin());

            if (pluginContainer.isPresent()) {
                Optional<Asset> optionalAsset;
                HoconConfigurationLoader tempLoader;

                for (String asset : optionalConfigAsset.assets()) {
                    optionalAsset = Sponge.getAssetManager().getAsset(asset);

                    if (optionalAsset.isPresent()) {
                        tempLoader = HoconConfigurationLoader.builder().setURL(optionalAsset.get().getUrl()).build();
                        node.mergeValuesFrom(tempLoader.load());
                    }
                }
            }
        }
    }

}

GlobalConfig.java

package com.kinggoesgaming.foundations.core.configs;

import com.kinggoesgaming.foundations.api.configuration.abstraction.concrete.ConcreteHoconConfiguration;
import com.kinggoesgaming.foundations.api.configuration.annotation.ConcreteConfigAsset;

import java.nio.file.Paths;

import static com.kinggoesgaming.foundations.core.FoundationsCore.getHeaders;
import static com.kinggoesgaming.foundations.core.FoundationsCore.getTargets;

/**
 *
 */
@ConcreteConfigAsset(
        plugin = "com.kingoesgaming.foundations.core",
        assets = "config/concrete/global.conf"
)
public class GlobalConfig extends ConcreteHoconConfiguration {

    public GlobalConfig() {
        file = Paths.get(getTargets().getNode("configs", "global").getString());
        header = getHeaders().getNode("configs", "global").getString();
        clazz = getClass();
    }
}

log.log

[16:24:23] [Server thread/ERROR] [Sponge]: Could not pass FMLInitializationEvent to org.spongepowered.mod.plugin.SpongeModPluginContainer@26e8ac89
java.lang.NullPointerException
	at com.kinggoesgaming.foundations.api.configuration.abstraction.concrete.ConcreteHoconConfiguration.load(ConcreteHoconConfiguration.java:51) ~[ConcreteHoconConfiguration.class:0.1.0]
	at com.kinggoesgaming.foundations.core.FoundationsCore.onInitialization(FoundationsCore.java:96) ~[FoundationsCore.class:?]
	at org.spongepowered.common.event.listener.GameInitializationEventListener_FoundationsCore_onInitialization1.handle(Unknown Source) ~[?:?]
	at org.spongepowered.common.event.RegisteredListener.handle(RegisteredListener.java:86) ~[RegisteredListener.class:1.8.9-1763-4.1.0-BETA-1212]
	at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:239) [SpongeModEventManager.class:1.8.9-1763-4.1.0-BETA-1212]
	at org.spongepowered.mod.event.SpongeModEventManager.post(SpongeModEventManager.java:283) [SpongeModEventManager.class:1.8.9-1763-4.1.0-BETA-1212]
	at org.spongepowered.mod.SpongeMod.onStateEvent(SpongeMod.java:183) [SpongeMod.class:1.8.9-1763-4.1.0-BETA-1212]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_74]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_74]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_74]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_74]
	at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.EventBus.post(EventBus.java:275) [minecraft_server.1.8.9.jar:?]
	at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:211) [LoadController.class:?]
	at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:189) [LoadController.class:?]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:1.8.0_74]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:1.8.0_74]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[?:1.8.0_74]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[?:1.8.0_74]
	at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304) [minecraft_server.1.8.9.jar:?]
	at com.google.common.eventbus.EventBus.post(EventBus.java:275) [minecraft_server.1.8.9.jar:?]
	at net.minecraftforge.fml.common.LoadController.redirect$onPost$0(LoadController.java:53) [LoadController.class:?]
	at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:118) [LoadController.class:?]
	at net.minecraftforge.fml.common.Loader.initializeMods(Loader.java:737) [Loader.class:?]
	at net.minecraftforge.fml.server.FMLServerHandler.finishServerLoading(FMLServerHandler.java:97) [FMLServerHandler.class:?]
	at net.minecraftforge.fml.common.FMLCommonHandler.onServerStarted(FMLCommonHandler.java:325) [FMLCommonHandler.class:?]
	at net.minecraft.server.dedicated.DedicatedServer.func_71197_b(DedicatedServer.java:205) [ko.class:?]
	at net.minecraft.server.MinecraftServer.run(MinecraftServer.java:441) [MinecraftServer.class:?]
	at java.lang.Thread.run(Thread.java:745) [?:1.8.0_74]