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--- documentation:fabric_loader [2020/02/22 00:55] – General cleanup jamieswhiteshirt
+++ documentation:fabric_loader [2023/12/27 12:57] (current) – ↷ Links adapted because of a move operation 194.190.81.32
@@ Line 4: / Line 4: @@
 Fabric Loader has services to allow mods to have some code executed during initialization, to transform classes, declare and provide mod dependencies, all in a number of different environments.
+For each Fabric Loader version, there is Javadoc available at
+<code>https://maven.fabricmc.net/docs/fabric-loader-[loader version]</code>
+For example, Fabric Loader 0.11.1's documentation is at https://maven.fabricmc.net/docs/fabric-loader-0.11.1/
 ===== Features =====
@@ Line 19: / Line 23: @@
 Nested JARs allow a mod to provide its own dependencies, so Fabric Loader can pick the best version matching the dependencies instead of requiring separate installation of dependencies. They also allow clean packaging of submodules, so each module can be used separately. Non-mod libraries can be repackaged as mods for nested JAR usage. A mod may bundle a number of other mods within its JAR. A nested JAR must itself also be a mod, which again can have nested JARs. Fabric Loader will load nested JARs while attempting to satisfy dependency constraints.
-Nested JARs are not extracted, they are instead loaded in in-memory file system using jimfs. See the [[https://fabricmc.net/wiki/tutorial:loader04x#nested_jars|guidelines]] for how to use nested JARs effectively. Nested JARs must be declared by their paths relative to the containing JAR's root.
+Nested JARs are not extracted, they are instead loaded in in-memory file system using jimfs. See the [[tutorial:loader04x#nested_jars|guidelines]] for how to use nested JARs effectively. Nested JARs must be declared by their paths relative to the containing JAR's root.
 ==== Entrypoints ====
@@ Line 58: / Line 62: @@
 Fabric Loader can also be launched with LegacyLauncher/LaunchWrapper using the tweakers ''net.fabricmc.loader.launch.FabricClientTweaker'' and ''net.fabricmc.loader.launch.FabricServerTweaker'' for clients and servers respectively. However, LegacyLauncher/LaunchWrapper support is currently outdated.
+===== Integrating Fabric Loader into a dedicated application =====
+As stated above, Fabric Loader can be used outside of Minecraft to add mod loading for Java applications. This section will briefly summarize what do you need to do to integrate Fabric loader to your Java game/dedicated app. This was tested with **Gradle 7** (specifically 7.3.1), **Java 8** and **IntelliJ IDEA 2022.3.1 (Community Edition)**.
+==== Gradle dependencies ====
+First, you'll need to add Fabric Loader as a dependency, and its dependencies in you ''build.gradle'':
+<code groovy>
+repositories {
+    // your other repositories...
+    maven {
+        url "https://repo.spongepowered.org/maven/"
+    }
+    maven {
+        url "https://maven.fabricmc.net/"
+    }
+}
+dependencies {
+    // your dependencies...
+    implementation "net.fabricmc:fabric-loader:0.13.0"
+    implementation "net.fabricmc:access-widener:2.1.0"
+    implementation "net.fabricmc:tiny-mappings-parser:0.2.2.14"
+    implementation "com.google.guava:guava:21.0"
+    implementation "com.google.code.gson:gson:2.8.7"
+    implementation "org.ow2.asm:asm:9.2"
+    implementation "org.ow2.asm:asm-analysis:9.2"
+    implementation "org.ow2.asm:asm-commons:9.2"
+    implementation "org.ow2.asm:asm-tree:9.2"
+    implementation "org.ow2.asm:asm-util:9.2"
+}
+</code>
+==== Launching your app with Fabric Loader ====
+If you've launched your app before through your own ''main(String[])'', to incorporate Fabric Loader into your app, you will need to set its main class to use one of the Knot launchers. For client-side (or if you don't have client/server separation), specify ''net.fabricmc.loader.impl.launch.knot.KnotClient'' as your main class. For server-side only, specify ''net.fabricmc.loader.impl.launch.knot.KnotServer''. You might ask, "but how will Fabric Loader know how to load my game?" That's where **GameProvider** comes into play.
+==== Setting up GameProvider ====
+**GameProvider** is an interface that lets Fabric Loader locate your game, configure Fabric launcher, and then finally launch the game. For Fabric Loader to instantiate your implementation of **GameProvider**, you need to define it as a service that can be found by [[https://docs.oracle.com/javase/8/docs/api/java/util/ServiceLoader.html|ServiceLoader]]. In your project's resources, create ''META-INF/services/net.fabricmc.loader.impl.game.GameProvider'' file, and paste into it the full class name to your **GameProvider**. Something like this:
+<code>
+net.developer.app.fabric.AppGameProvider
+</code>
+This should allow Fabric Loader find your **GameProvider**. Now let's breakdown **GameProvider** interface.
+=== Implementing GameProvider ===
+For your game actually to launch, you need to carefully implement **GameProvider** in a specific way. Here is a breakdown of each method does:
+  * ''getGameId()'' and ''getGameName()'', self-explanatory, app's ID like ''epic_app'', and app's name ''Epic App''.
+  * ''getRawGameVersion()'' and ''getNormalizedGameVersion()'', it's not entirely clear, but raw version can include git-hash, or any information about the game that developer may want to know (like ''v0.1.2+build17#f73acde''), while normalized version seems to be for display (like ''v0.1.2'').
+  * ''getBuiltinMods()'' allows you to provide built-in mod(s), which can be used by mods to target specific version, but it's completely optional, and you can just return ''Collections.emptyList()''.
+  * ''getEntryPoint()'', full class name of your main app class. It seems to be used only in Minecraft.
+  * ''getLaunchDirectory()'' is a very important method. It should return where the app's resources folder is (like configs, data, saves, etc.). That's where Fabric Loader will create ''config'' and ''mods'' folder, and from which mods will be loaded from!
+  * ''isObfuscated()'' whether your app is obfuscated.
+  * ''requiresUrlClassLoader()'' it forces **Fabric Loader** to use a different compatibility class loader.
+  * ''isEnabled()'' whether your app is enabled. Just ''return true;''
+  * ''locateGame(FabricLauncher, String[])'' that's where you need to parse the arguments with ''net.fabricmc.loader.impl.util.Arguments'', locate the game directory and ''return true;'' if game directory was found.
+  * ''initialize(FabricLauncher)'' here you can add extra configuration to **FabricLauncher**. **Don't initialize your game here**!
+  * ''getEntryPointTransformer()'' return a ''net.fabricmc.loader.impl.game.patch.GameTransformer'' that does extra modification on the app's jar. If you're setting up Fabric Loader to work with a separate app which you currently aren't developing in your development environment, then simply return a subclass of **GameTransformer** that returns ''null'' in its ''transform(String)'' method.
+  * ''unlockClassPath(FabricLauncher)'' is called after transformers (i.e. Mixin) were initialized and mods were detected and loaded (but not initialized).
+  * ''launch(ClassLoader)'' this is where you launch your app. **Important**: the app must be launched through reflection using the given **ClassLoader**, about that later.
+  * ''getArguments()'' simply return the ''Arguments'' instance you initialized in ''locateGame(FabricLauncher, String[]))''.
+  * ''getLaunchArguments(boolean)'' simply ''return this.getArguments.toArray()''.
+An example **GameProvider** would look like this:
+<code java>
+public class AppGameProvider implements GameProvider
+{
+    private Arguments arguments;
+    private Path gameDirectory;
+    private GameTransformer transformer = new AppGameTransformer();
+    @Override
+    public String getGameId()
+    {
+        return "app";
+    }
+    @Override
+    public String getGameName()
+    {
+        return "App";
+    }
+    @Override
+    public String getRawGameVersion()
+    {
+        return App.FULL_VERSION;
+    }
+    @Override
+    public String getNormalizedGameVersion()
+    {
+        return App.VERSION;
+    }
+    @Override
+    public Collection<BuiltinMod> getBuiltinMods()
+    {
+        return Collections.emptyList();
+    }
+    @Override
+    public String getEntrypoint()
+    {
+        return "net.developer.app.App";
+    }
+    @Override
+    public Path getLaunchDirectory()
+    {
+        return this.gameDirectory;
+    }
+    @Override
+    public boolean isObfuscated()
+    {
+        return false;
+    }
+    @Override
+    public boolean requiresUrlClassLoader()
+    {
+        return false;
+    }
+    @Override
+    public boolean isEnabled()
+    {
+        return true;
+    }
+    @Override
+    public boolean locateGame(FabricLauncher launcher, String[] args)
+    {
+        this.arguments = new Arguments();
+        this.arguments.parse(args);
+        this.gameDirectory = Paths.get(this.arguments.get("gameDirectory"));
+        return Files.isDirectory(this.gameDirectory);
+    }
+    @Override
+    public void initialize(FabricLauncher launcher)
+    {}
+    @Override
+    public GameTransformer getEntrypointTransformer()
+    {
+        return this.transformer;
+    }
+    @Override
+    public void unlockClassPath(FabricLauncher launcher)
+    {
+        for (Path path : this.jars)
+        {
+            launcher.addToClassPath(path);
+        }
+    }
+    @Override
+    public void launch(ClassLoader loader)
+    {
+        try
+        {
+            Class main = loader.loadClass(this.getEntrypoint());
+            Method method = main.getMethod("main", String[].class);
+            method.invoke(null, (Object) this.arguments.toArray());
+        }
+        catch (Exception e)
+        {
+            e.printStackTrace();
+        }
+    }
+    @Override
+    public Arguments getArguments()
+    {
+        return this.arguments;
+    }
+    @Override
+    public String[] getLaunchArguments(boolean sanitize)
+    {
+        return this.arguments.toArray();
+    }
+}
+</code>
+This class example assumes that argument ''--gameDirectory'' is the one that specifies where app's working directory is located. Adjust if needed.
+==== Final touches ====
+Once you get Fabric Loading up and running in your app, you would see extra log in the console upon launching your app (if you did everything correctly):
+<code>
+[14:20:00] [INFO] [FabricLoader/GameProvider]: Loading App 0.1 (dev) with Fabric Loader 0.13.0
+[14:20:00] [INFO] [FabricLoader/]: Loading 2 mods:
+	- fabricloader 0.13.0
+	- java 8
+[14:20:01] [WARN] [FabricLoader/ModRemap]: Runtime mod remapping disabled due to no fabric.remapClasspathFile being specified. You may need to update loom.
+[14:20:01] [INFO] [FabricLoader/Mixin]: SpongePowered MIXIN Subsystem Version=0.8.5 Source=file:/C:/Users/Developer/.gradle/caches/modules-2/files-2.1/org.spongepowered/mixin/0.8.5/9d1c0c3a304ae6697ecd477218fa61b850bf57fc/mixin-0.8.5.jar Service=Knot/Fabric Env=CLIENT
+[14:20:01] [INFO] [FabricLoader/Mappings]: Mappings not present!
+</code>
+That's a good sign. However, that's not all.
+=== Initializing mods ===
+If you would try making a mod for your app either as a separate project or as a submodule in your project, there could be a couple of things that may not work either in development or in release. First thing is mods won't initialize. I.e. ''ModInitializer.onInitialize()'' won't be called. To fix that, simply call ''net.fabricmc.loader.impl.game.minecraft.Hooks.startClient(File, Object)'' (where ''File'' is game directory, and ''Object'' could be the main object of your game) somewhere after you initialized event busses, base registries, etc. so that mods could start modding your app.
+Something like this:
+<code java>
+    public MainApp(App app)
+    {
+        super();
+        this.development = app.development;
+        this.events.register(this);
+        this.registerCore(this, app.gameDirectory);
+        this.registerFactories();
+        this.registerFoundation();
+        this.registerMiscellaneous();
+        Hooks.startClient(app.gameDirectory, app);
+        if (this.development)
+        {
+            this.watchDog = new WatchDog(this.assetsFolder);
+            this.watchDog.register(this.textures);
+            this.watchDog.register(this.models);
+            this.watchDog.register(this.sounds);
+            this.watchDog.start();
+        }
+    }
+</code>
+=== Mixins don't work? ===
+And finally, even if you registered Mixins in your mod, they may load, but they won't be able to actually patch their target class. If you have following message in the log:
+<code>
+[12:20:05] [WARN] [FabricLoader/Knot]: * CLASS LOADER MISMATCH! THIS IS VERY BAD AND WILL PROBABLY CAUSE WEIRD ISSUES! *
+ - Expected game class loader: net.fabricmc.loader.impl.launch.knot.KnotClassLoader@446a1e84
+ - Actual game class loader: null
+Could not find the expected class loader in game class loader parents!
+</code>
+Then it's the root of the issue. To fix this, you need to add your app's jar, or folder (in development) to ''FabricLauncher'''s class path. This could be done by looking in the class path for your jar/folder, and detecting some key files unique to your app. Here is what you can do:
+<code java>
+public class AppGameProvider implements GameProvider
+{
+    /* ... */
+    private List<Path> jars = new ArrayList<Path>();
+    private Set<String> jarFiles;
+    public AppGameProvider()
+    {
+        this.jarFiles = new HashSet<String>();
+        this.jarFiles.add("net/developer/app/App.class");
+        this.jarFiles.add("net/developer/app/MainApp.class");
+    }
+    /* ... */
+    @Override
+    public boolean locateGame(FabricLauncher launcher, String[] args)
+    {
+        this.arguments = new Arguments();
+        this.arguments.parse(args);
+        this.gameDirectory = Paths.get(this.arguments.get("gameDirectory"));
+        for (Path path : launcher.getClassPath())
+        {
+            if (this.isHostApp(path))
+            {
+                this.jars.add(path);
+            }
+        }
+        return Files.isDirectory(this.gameDirectory);
+    }
+    private boolean isHostApp(Path path)
+    {
+        if (Files.isDirectory(path))
+        {
+            for (String string : this.jarFiles)
+            {
+                if (Files.exists(path.resolve(string)))
+                {
+                    return true;
+                }
+            }
+            return false;
+        }
+        try (ZipFile zip = new ZipFile(path.toFile()))
+        {
+            for (String string : this.jarFiles)
+            {
+                if (zip.getEntry(string) != null)
+                {
+                    return true;
+                }
+            }
+        }
+        catch (Exception e)
+        {
+            e.printStackTrace();
+        }
+        return false;
+    }
+    /* ... */
+    @Override
+    public void unlockClassPath(FabricLauncher launcher)
+    {
+        for (Path path : this.jars)
+        {
+            launcher.addToClassPath(path);
+        }
+    }
+    /* ... */
+}
+</code>
+After detecting the app's jar(s)/folder(s) and adding them to ''FabricLauncher'''s class path, Mixins should work in both development and release environment after that.
+=== Loading mods from classpath ===
+If you're testing the mod from the submodule that has your app and Fabric Loader in the classpath, instead of compiling the mod and placing it into app's launch directory, for Fabric Loader to load your mod from classpath, you need to add ''-Dfabric.development=true'' to JVM flags when running it, then mod(s) from classpath would be loaded too.
+For more reference check out [[https://github.com/FabricMC/fabric-loader|Fabric Loader's]] source, ''net.fabricmc.loader.impl.game.minecraft.MinecraftGameProvider'', and this [[https://github.com/PseudoDistant/ExampleGameProvider|GameProvider example]].