Dependency Injection

Sponge uses dependency injection to provide instances of the API to plugins. Dependency injection allows plugins to designate a few API types that will be injected after construction.

Temporary List of Injected Types

ConfigDir (annotation on Path or File): Used to inject the plugin’s configuration directory: ./config/ OR ./config/<Plugin#id>/ depending on ConfigDir#sharedRoot()
DefaultConfig (annotation on Path, ConfigurationLoader or File): Used to inject the plugin’s specific configuration file: <Plugin#id>.conf
AssetId (annotation on Asset): Used to inject a Asset from the asset folder of the plugin
AsynchronousExecutor (annotation on SpongeExecutorService): Used to inject the plugin’s specific AsynchronousExecutor
SynchronousExecutor (annotation on SpongeExecutorService): Used to inject the plugin’s specific SynchronousExecutor
ChannelId (annotation on ChannelBinding.IndexedMessageChannel or ChannelBinding.RawDataChannel): Used to inject a ChannelBinding with the given channel id
Asset: Must be annotated with @AssetId.
SpongeExecutorService: Must be annotated with either @AsynchronousExecutor or @SynchronousExecutor. Depending on the annotation given this will contain a reference to the plugin’s specific Asynchronous or Synchronous Executor.
ConfigurationLoader<CommentedConfigurationNode>: Must be annotated with @DefaultConfig. Used to inject a pre-generated ConfigurationLoader for the File of the same annotation.
EventManager: Manages the registration of event handlers and the dispatching of events.
File: Must be annotated with either @DefaultConfig or @ConfigDir. Depending on the annotation given this will contain a file reference to the plugins default config file or the directory used for storing configuration files. However, Path (see below) should be preferred.
Game: The Game object is the core accessor of SpongeAPI.
GameRegistry: Provides an easy way to retrieve types from a Game.
GuiceObjectMapperFactory: A tool provided by Configurate to allow easier mapping of objects to configuration nodes. See Serializing Objects for usage.
Injector: com.google.inject.Injector is available from Guice, it is the injector that was used to inject your plugin’s dependencies. You can use it to create a child injector with your own module in order to inject your own classes with either the Sponge provided dependencies listed on this page, or configure your own classes
Logger: Used to identify the plugin from which logged messages are sent.
Path: Must be annotated with either @DefaultConfig or @ConfigDir. Depending on the annotation given this will contain a path reference to the plugins default config file or the directory used for storing configuration files.
PluginContainer: A Plugin class wrapper, used to retrieve information from the annotation for easier use.
PluginManager: Manages the plugins loaded by the implementation. Can retrieve another plugin’s PluginContainer.

Injection Examples

There are a few references which are difficult to get - or, in some cases, impossible - without injection. While these may not be absolutely vital to every plugin, they’re quite frequently used.

Note

Remember that it’s almost always best practice to inject your objects within the main class, as it’s instantiated with the Guice injector when the plugin is loaded.

Logger

Tip

View Logging and Debugging for a complete guide, specifically for the Logger.

Game

The Game object is the opening for many of the internal functions of SpongeAPI, from the EventManager to the Server and even the Sync/Async Scheduler.

While it is entirely possible to retrieve the Game object through Sponge.getGame(), it is commonly obtained through an injection.

Example - Field

import com.google.inject.Inject;
import org.spongepowered.api.Game;

@Inject
private Game game;

Example - Method

private Game game;

@Inject
private void setGame(Game game) {
    this.game = game;
}

Example - Constructor

For the purpose of this tutorial, “Apple” is the class name.

private Game game;

@Inject
public Apple(Game game) {
    this.game = game;
}

Config Directory

The recommended way to obtain your config file is through Guice, along with the ConfigDir annotation.

Tip

If you set sharedRoot to true, your ConfigDir will be the same directory which - potentially - houses the configuration for other plugins. In most cases where grabbing the ConfigDir is required, this should be false.

Example - Field

import org.spongepowered.api.config.ConfigDir;

import java.nio.file.Path;

@Inject
@ConfigDir(sharedRoot = false)
private Path configDir;

Example - Method

private Path configDir;

@Inject
private void setConfigDir(@ConfigDir(sharedRoot = false) Path configDir) {
    this.configDir = configDir;
}

Example - Constructor

For the purposes of this tutorial, “Orange” is the class name.

private Path configDir;

@Inject
public Orange(@ConfigDir(sharedRoot = false) Path configDir) {
    this.configDir = configDir;
}

DefaultConfig

The way that @DefaultConfig works is very similar to @ConfigDir. The biggest difference is that @DefaultConfig refers to a specific file, whereas @ConfigDir refers to a directory.

Tip

View Configuring Plugins for a complete guide, specifically for @DefaultConfig.