PrismLauncher/libraries/launcher/org/prismlauncher/utils/ReflectionUtils.java

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package org.prismlauncher.utils;
import java.applet.Applet;
import java.io.File;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.MethodType;
import java.lang.reflect.Field;
import java.lang.reflect.Modifier;
import java.util.logging.Level;
import java.util.logging.Logger;
public final class ReflectionUtils {
private static final Logger LOGGER = Logger.getLogger("ReflectionUtils");
private ReflectionUtils() {
}
/**
* Instantiate an applet class by name
*
* @param appletClassName The name of the applet class to resolve
*
* @return The instantiated applet class
*
* @throws ClassNotFoundException if the provided class name cannot be found
* @throws NoSuchMethodException if the no-args constructor cannot be found
* @throws IllegalAccessException if the constructor cannot be accessed via method handles
* @throws Throwable any exceptions from the class's constructor
*/
public static Applet createAppletClass(String appletClassName) throws Throwable {
Class<?> appletClass = ClassLoader.getSystemClassLoader().loadClass(appletClassName);
MethodHandle appletConstructor = MethodHandles.lookup().findConstructor(appletClass, MethodType.methodType(void.class));
return (Applet) appletConstructor.invoke();
}
/**
* Finds a field that looks like a Minecraft base folder in a supplied class
*
* @param minecraftMainClass the class to scan
*
* @return The found field.
*/
public static Field getMinecraftGameDirField(Class<?> minecraftMainClass) {
LOGGER.fine("Resolving minecraft game directory field");
// Field we're looking for is always
// private static File obfuscatedName = null;
for (Field field : minecraftMainClass.getDeclaredFields()) {
// Has to be File
if (field.getType() != File.class) {
continue;
}
int fieldModifiers = field.getModifiers();
// Must be static
if (!Modifier.isStatic(fieldModifiers)) {
LOGGER.log(Level.FINE, "Rejecting field {0} because it is not static", field.getName());
continue;
}
// Must be private
if (!Modifier.isPrivate(fieldModifiers)) {
LOGGER.log(Level.FINE, "Rejecting field {0} because it is not private", field.getName());
continue;
}
// Must not be final
if (Modifier.isFinal(fieldModifiers)) {
LOGGER.log(Level.FINE, "Rejecting field {0} because it is final", field.getName());
continue;
}
LOGGER.log(Level.FINE, "Identified field {0} to match conditions for minecraft game directory field", field.getName());
return field;
}
return null;
}
/**
* Resolve main entrypoint and returns method handle for it.
* <p>
* Resolves a method that matches the following signature
* <code>
* public static void main(String[] args) {
* <p>
* }
* </code>
*
* @param entrypointClass The entrypoint class to resolve the method from
*
* @return The method handle for the resolved entrypoint
*
* @throws NoSuchMethodException If no method matching the correct signature can be found
* @throws IllegalAccessException If method handles cannot access the entrypoint
*/
public static MethodHandle findMainEntrypoint(Class<?> entrypointClass) throws NoSuchMethodException, IllegalAccessException {
return MethodHandles.lookup().findStatic(entrypointClass, "main", MethodType.methodType(void.class, String[].class));
}
/**
* Resolve main entrypoint and returns method handle for it.
* <p>
* Resolves a method that matches the following signature
* <code>
* public static void main(String[] args) {
* <p>
* }
* </code>
*
* @param entrypointClassName The name of the entrypoint class to resolve the method from
*
* @return The method handle for the resolved entrypoint
*
* @throws ClassNotFoundException If a class cannot be found with the provided name
* @throws NoSuchMethodException If no method matching the correct signature can be found
* @throws IllegalAccessException If method handles cannot access the entrypoint
*/
public static MethodHandle findMainEntrypoint(String entrypointClassName) throws
ClassNotFoundException,
NoSuchMethodException,
IllegalAccessException {
return findMainEntrypoint(ClassLoader.getSystemClassLoader().loadClass(entrypointClassName));
}
}