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change addon classloading
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@Jsinco
Jsinco committed Jan 8, 2025
1 parent 6f0a678 commit 8849faf
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Showing 2 changed files with 52 additions and 63 deletions.
113 changes: 50 additions & 63 deletions src/main/java/com/dre/brewery/api/addons/AddonManager.java
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Original file line number Diff line number Diff line change
Expand Up @@ -22,16 +22,13 @@

import com.dre.brewery.BreweryPlugin;
import com.dre.brewery.utility.Logging;
import com.dre.brewery.utility.Tuple;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.lang.reflect.Field;
import java.net.URL;
import java.net.URLClassLoader;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.ConcurrentLinkedQueue;
import java.util.jar.JarEntry;
import java.util.jar.JarInputStream;
Expand All @@ -40,7 +37,7 @@
/**
* Yep, you guessed it. This is the class that manages all the addons. It loads them, unloads them, reloads them, and keeps track of them.
* <p>
* Basically just copies what Bukkit's plugin loader does, but on a much, much smaller scale.
* Kind of similar to how the PluginManager in Bukkit works, but for addons.
*
* @see BreweryAddon
* @see AddonInfo
Expand All @@ -64,29 +61,44 @@ public AddonManager(BreweryPlugin plugin) {
}

public void unloadAddons() {
if (LOADED_ADDONS.isEmpty()) {
return;
}

Logging.log("Disabling " + LOADED_ADDONS.size() + " loaded addon(s)...");
for (BreweryAddon addon : LOADED_ADDONS) {
try {
addon.onAddonDisable();
addon.unregisterListeners();
addon.unregisterCommands();
} catch (Throwable t) {
Logging.errorLog("Failed to disable addon " + addon.getClass().getSimpleName(), t);
}
unloadAddon(addon);
}
int loaded = LOADED_ADDONS.size();
if (loaded > 0) Logging.log("Disabled " + loaded + " addon(s)");
LOADED_ADDONS.clear();
}

public void unloadAddon(BreweryAddon addon) {
if (addon == null) {
Logging.warningLog("Tried to unload an addon that doesn't exist.");
return;
}
String n = addon.getAddonInfo() == null ? addon.getClass().getSimpleName() : addon.getAddonInfo().name();
try {
addon.onAddonDisable();
} catch (Throwable t) {
Logging.errorLog("Failed to disable addon " + n, t);
}
try {
addon.unregisterListeners();
addon.unregisterCommands();
} catch (Throwable t) {
Logging.errorLog("Failed to disable addon " + addon.getClass().getSimpleName(), t);
Logging.errorLog("Failed to unregister listeners/commands for addon " + n, t);
}
try {
Field field = BreweryAddon.class.getDeclaredField("classLoader");
field.setAccessible(true);
URLClassLoader classLoader = (URLClassLoader) field.get(addon);
classLoader.close();
field.set(addon, null);
LOADED_ADDONS.remove(addon);
} catch (Throwable t) {
Logging.errorLog("Failed to unload addon " + n, t);
Logging.warningLog("Addon " + n + "'s ClassLoader has not been closed properly!");
}
LOADED_ADDONS.remove(addon);
}


Expand All @@ -107,7 +119,6 @@ public ConcurrentLinkedQueue<BreweryAddon> getAddons() {
}


// Get all classes that extend Addon and instantiates them
public void loadAddons() {
File[] files = addonsFolder.listFiles((dir, name) -> name.endsWith(".jar")); // Get all files in the addons folder that end with .jar
if (files == null) {
Expand Down Expand Up @@ -136,15 +147,21 @@ public void enableAddons() {

/**
* Load the addon from a jar file.
* Basically just scan the whole jar file for our BreweryAddon class, init that class first, init all other classes in the jar,
* set all the fields reflectively, and then call the onAddonPreEnable method.
* onAddonPreEnable() will be called after the addon is loaded.
* @param file The jar file to load the addon from
*/
public void loadAddon(File file) {
try (URLClassLoader classLoader = new URLClassLoader(new URL[]{file.toURI().toURL()}, getClass().getClassLoader())) {
var pair = getClassesFromJar(file, classLoader); // Get all our loaded classes.
Class<? extends BreweryAddon> mainClass = pair.first();
List<Class<?>> classes = pair.second();
try {

// We have to use the same class loader used to load this class AKA, the 'PluginLoader' class provided by Bukkit.
// Only classes loaded by the same ClassLoader can access each other.
// So to prevent any issues,
// we're using the same ClassLoader that loaded this class to load the classes from the jar.
URLClassLoader classLoader = new URLClassLoader(
new URL[]{file.toURI().toURL()},
this.getClass().getClassLoader() // <-- PluginClassLoader
);
var mainClass = getMainClass(file, classLoader); // Get all our loaded classes.

BreweryAddon addon;
try {
Expand All @@ -167,11 +184,13 @@ public void loadAddon(File file) {

// Set all the fields for our addon reflectively.

Field classLoaderField = BreweryAddon.class.getDeclaredField("classLoader"); classLoaderField.setAccessible(true);
Field loggerField = BreweryAddon.class.getDeclaredField("logger"); loggerField.setAccessible(true);
Field fileManagerField = BreweryAddon.class.getDeclaredField("addonFileManager"); fileManagerField.setAccessible(true);
Field addonConfigManagerField = BreweryAddon.class.getDeclaredField("addonConfigManager"); addonConfigManagerField.setAccessible(true);
Field addonFile = BreweryAddon.class.getDeclaredField("addonFile"); addonFile.setAccessible(true);

classLoaderField.set(addon, classLoader);
loggerField.set(addon, new AddonLogger(addon.getAddonInfo()));
fileManagerField.set(addon, new AddonFileManager(addon, file));
addonConfigManagerField.set(addon, new AddonConfigManager(addon));
Expand All @@ -188,46 +207,20 @@ public void loadAddon(File file) {
unloadAddon(addon);
}

// Now that we're done loading our main class, we can go ahead and load the rest of our classes. We don't care about the order of these classes.
for (Class<?> clazz : classes) {
if (BreweryAddon.class.isAssignableFrom(clazz)) { // Just make sure it's not our main class we're trying to load again.
continue;
}
try {
classLoader.loadClass(clazz.getName());
} catch (ClassNotFoundException e) {
plugin.getLogger().log(Level.SEVERE, "Failed to load class " + clazz.getName(), e);
}
}

} catch (Throwable ex) {
Logging.errorLog("Failed to load addon classes from jar " + file.getName(), ex);
}
}

/**
* It's about time I document this...
* <p>
* What we're doing here is trying to recreate what Bukkit does to load plugins. Obviously the code could be cleaned up and spread out to
* multiple functions, but I honestly can't be bothered and this is fine I guess.
* <p>
* We have to load each class file, but first, we must load the class which extends BreweryAddon (our main class) before all else. If we
* don't load this class first we can get some nasty race conditions. Also, plugin developers expect their main class to be loaded first
* (as with all java programs) so we must first figure out which class extends BreweryAddon, load that one, then load the rest of the classes
* packaged in the addon.
* @param jarFile The jar file to load classes from
* @return A list of classes loaded from the jar
* Searches the addon's jar file for the main class that extends BreweryAddon.
* @param jarFile The jar file to search
* @param classLoader The class loader to use
* @return The main class that extends BreweryAddon
*/
private Tuple<Class<? extends BreweryAddon>, List<Class<?>>> getClassesFromJar(File jarFile, ClassLoader classLoader) {
List<Class<?>> classes = new ArrayList<>();
Class<? extends BreweryAddon> mainClass = null;

// We have to use the same class loader used to load this class AKA, the 'PluginLoader' class provided by Bukkit.
// ClassLoaders in Java are pretty interesting, and only classes loaded by the same ClassLoader can access each other.
// So to prevent any issues, we're using the same ClassLoader that loaded this class to load the classes from the jar.
private Class<? extends BreweryAddon> getMainClass(File jarFile, ClassLoader classLoader) {
try (JarInputStream jarInputStream = new JarInputStream(new FileInputStream(jarFile))) {
JarEntry jarEntry;
String mainDir = "";
while ((jarEntry = jarInputStream.getNextJarEntry()) != null) { // Just iterate through every file in the jar file and check if it's a compiled java class.
if (jarEntry.getName().endsWith(".class")) {

Expand All @@ -236,7 +229,7 @@ private Tuple<Class<? extends BreweryAddon>, List<Class<?>>> getClassesFromJar(F
try {
Class<?> clazz;
try {
// It's important that we don't initialize any other classes before our main class.
// We don't want to initialize any classes. We'll leave that up to the JVM.
clazz = Class.forName(className, false, classLoader);
} catch (ClassNotFoundException | NoClassDefFoundError e) {
Logging.errorLog("An exception occurred while trying to load a class from an addon", e);
Expand All @@ -245,14 +238,8 @@ private Tuple<Class<? extends BreweryAddon>, List<Class<?>>> getClassesFromJar(F
if (BreweryAddon.class.isAssignableFrom(clazz)) {
// Found our main class, we're going to load it now.
classLoader.loadClass(className);
mainDir = className.substring(0, className.lastIndexOf('.'));
mainClass = clazz.asSubclass(BreweryAddon.class);
}
// Prevents loading classes that aren't in the same package. Addons that have dependencies better shade em in I guess. (TODO: remove this?)
if (!clazz.getName().contains(mainDir)) {
continue;
return clazz.asSubclass(BreweryAddon.class);
}
classes.add(clazz); // And finally... add the class to our list of classes.

} catch (ClassNotFoundException e) {
plugin.getLogger().log(Level.SEVERE, "Failed to load class " + className, e);
Expand All @@ -264,7 +251,7 @@ private Tuple<Class<? extends BreweryAddon>, List<Class<?>>> getClassesFromJar(F
} catch (IOException e) {
plugin.getLogger().log(Level.SEVERE, "Failed to load classes from jar " + jarFile.getName(), e);
}
return new Tuple<>(mainClass, classes);
throw new IllegalStateException("No class extending BreweryAddon found in jar " + jarFile.getName());
}

}
2 changes: 2 additions & 0 deletions src/main/java/com/dre/brewery/api/addons/BreweryAddon.java
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Original file line number Diff line number Diff line change
Expand Up @@ -84,6 +84,8 @@ public abstract class BreweryAddon {
private final List<Listener> listeners = new ArrayList<>();
private final List<String> commands = new ArrayList<>();

private URLClassLoader classLoader;

private AddonInfo addonInfo;

private AddonLogger logger;
Expand Down

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