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Add support for Java 16 (#1120)

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Switched from the now-unavailable ClassLoader::defineClass method to the java.lang.invoke.MethodHandles.Lookup::defineClass. This is available on Java 9+.
This commit is contained in:
Pim van der Loos 2021-04-05 05:03:05 +02:00 committed by GitHub
parent 97972acee8
commit 7ce3f471bf
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1 changed files with 51 additions and 21 deletions
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54
src/main/java/com/comphenix/protocol/reflect/compiler/StructureCompiler.java
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@ -141,6 +141,18 @@ public final class StructureCompiler {
private static String COMPILED_CLASS = PACKAGE_NAME + "/CompiledStructureModifier";
private static String FIELD_EXCEPTION_CLASS = "com/comphenix/protocol/reflect/FieldAccessException";
// On java 9+ (53.0+) CLassLoader#defineClass(String, byte[], int, int) should not be used anymore.
// It will throw warnings and on Java 16+ (60.0+), it does not work at all anymore.
private static final boolean LEGACY_CLASS_DEFINITION =
Float.parseFloat(System.getProperty("java.class.version")) < 53;
/**
* The MethodHandles.Lookup object for this compiler. Only used when using the modern defineClass strategy.
*/
private Object lookup = null;
// Used to get the MethodHandles.Lookup object on newer versions of Java.
private volatile static Method lookupMethod;
public static boolean attemptClassLoad = false;
/**
@ -289,36 +301,54 @@ public final class StructureCompiler {
byte[] data = cw.toByteArray();
// Call the define method
try {
Class<?> clazz = defineClass(data);
// DEBUG CODE: Print the content of the generated class.
//org.objectweb.asm.ClassReader cr = new org.objectweb.asm.ClassReader(data);
//cr.accept(new ASMifierClassVisitor(new PrintWriter(System.out)), 0);
return clazz;
}
private Class<?> defineClassLegacy(byte[] data) throws InvocationTargetException, IllegalAccessException,
NoSuchMethodException {
if (defineMethod == null) {
Method defined = ClassLoader.class.getDeclaredMethod("defineClass",
new Class<?>[] { String.class, byte[].class, int.class, int.class });
new Class<?>[]{String.class, byte[].class, int.class, int.class});
// Awesome. Now, create and return it.
defined.setAccessible(true);
defineMethod = defined;
}
return (Class<?>) defineMethod.invoke(loader, null, data, 0, data.length);
}
@SuppressWarnings("rawtypes")
Class clazz = (Class) defineMethod.invoke(loader, null, data, 0, data.length);
private Class<?> defineClassModern(byte[] data) throws InvocationTargetException, IllegalAccessException,
ClassNotFoundException, NoSuchMethodException {
if (defineMethod == null) {
defineMethod = Class.forName("java.lang.invoke.MethodHandles$Lookup")
.getDeclaredMethod("defineClass", byte[].class);
}
if (lookupMethod == null) {
lookupMethod = Class.forName("java.lang.invoke.MethodHandles").getDeclaredMethod("lookup");
}
if (lookup == null)
lookup = lookupMethod.invoke(null);
// DEBUG CODE: Print the content of the generated class.
//org.objectweb.asm.ClassReader cr = new org.objectweb.asm.ClassReader(data);
//cr.accept(new ASMifierClassVisitor(new PrintWriter(System.out)), 0);
return clazz;
return (Class<?>) defineMethod.invoke(lookup, data);
}
private Class<?> defineClass(byte[] data) {
try {
return LEGACY_CLASS_DEFINITION ? defineClassLegacy(data) : defineClassModern(data);
} catch (SecurityException e) {
throw new RuntimeException("Cannot use reflection to dynamically load a class.", e);
} catch (NoSuchMethodException e) {
} catch (NoSuchMethodException | ClassNotFoundException e) {
throw new IllegalStateException("Incompatible JVM.", e);
} catch (IllegalArgumentException e) {
throw new IllegalStateException("Cannot call defineMethod - wrong JVM?", e);
} catch (IllegalAccessException e) {
throw new RuntimeException("Security limitation! Cannot dynamically load class.", e);
} catch (InvocationTargetException e) {
throw new RuntimeException("Error occured in code generator.", e);
throw new RuntimeException("Error occurred in code generator.", e);
}
}