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ReflectionHelper.java
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ReflectionHelper.java
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package com.denizenscript.denizencore.utilities;
import com.denizenscript.denizencore.utilities.debugging.Debug;
import sun.misc.Unsafe;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;
import java.util.stream.Collectors;
public class ReflectionHelper {
public static boolean hasInitialized = false;
private static final Map<Class, CheckingFieldMap> cachedFields = new HashMap<>();
private static final Map<Class, Map<String, MethodHandle>> cachedFieldSetters = new HashMap<>();
public static void echoError(String message) {
if (hasInitialized) {
Debug.echoError("[ReflectionHelper]" + message);
}
else {
System.err.println("[Denizen] [ReflectionHelper]: " + message);
}
}
public static void echoError(Throwable ex) {
if (hasInitialized) {
Debug.echoError(ex);
}
else {
ex.printStackTrace();
}
}
public static void setFieldValue(Class clazz, String fieldName, Object object, Object value) {
try {
getFields(clazz).get(fieldName).set(object, value);
}
catch (Throwable ex) {
echoError(ex);
}
}
public static <T> T getFieldValue(Class clazz, String fieldName, Object object) {
Map<String, Field> cache = getFields(clazz);
try {
Field field = cache.get(fieldName);
if (field == null) {
return null;
}
return (T) field.get(object);
}
catch (Throwable ex) {
echoError(ex);
return null;
}
}
public static class CheckingFieldMap extends HashMap<String, Field> {
public Class<?> clazz;
public CheckingFieldMap(Class<?> clazz) {
this.clazz = clazz;
}
public Field getFirstOfType(Class fieldClazz) {
for (Field f : super.values()) {
if (f.getType().equals(fieldClazz)) {
return f;
}
}
echoError("Reflection field missing - Tried to find field of type '" + fieldClazz.getCanonicalName() + "' of class '" + clazz.getCanonicalName() + "'.");
return null;
}
@Override
public Field get(Object name) {
Field f = super.get(name);
if (f == null) {
echoError("Reflection field missing - Tried to read field '" + name + "' of class '" + clazz.getCanonicalName() + "'.");
}
return f;
}
public Field get(String name, Class expected) {
Field f = get(name);
if (f == null) {
return null;
}
if (f.getType() != expected) {
echoError("Reflection field incorrect type - read field '" + name + "' from class '" + clazz.getCanonicalName() + "', expected type '" + expected.getCanonicalName() + "' but is type '" + f.getType().getCanonicalName() + "'");
}
return f;
}
public Field getNoCheck(String name) {
return super.get(name);
}
}
public static CheckingFieldMap getFields(Class clazz) {
CheckingFieldMap fields = cachedFields.get(clazz);
if (fields != null) {
return fields;
}
fields = new CheckingFieldMap(clazz);
for (Field field : clazz.getDeclaredFields()) {
field.setAccessible(true);
fields.put(field.getName(), field);
}
cachedFields.put(clazz, fields);
return fields;
}
public static Method getMethod(Class<?> clazz, String method, Class<?>... params) {
Method f = null;
try {
if (method == null) {
for (Method possible : clazz.getDeclaredMethods()) {
if (possible.getParameterCount() == params.length && Arrays.equals(possible.getParameterTypes(), params)) {
f = possible;
break;
}
}
}
else {
f = clazz.getDeclaredMethod(method, params);
f.setAccessible(true);
}
}
catch (Exception ex) {
echoError(ex);
}
if (f == null) {
echoError("Reflection method missing - Tried to read method '" + method + "' of class '" + clazz.getCanonicalName() + "'.");
}
return f;
}
public static MethodHandle getConstructor(Class<?> clazz, Class<?>... params) {
try {
Constructor<?> ctor = clazz.getDeclaredConstructor(params);
ctor.setAccessible(true);
MethodHandle result = LOOKUP.unreflectConstructor(ctor);
if (result != null) {
return result;
}
}
catch (Throwable ex) {
echoError(ex);
}
echoError("[ReflectionHelper]: Cannot find constructor for class '" + clazz.getCanonicalName() + "' with params: ["
+ Arrays.stream(params).map(Class::getCanonicalName).collect(Collectors.joining(", ")) + "]");
return null;
}
public static MethodHandle getMethodHandle(Class<?> clazz, String method, Class<?>... params) {
try {
return LOOKUP.unreflect(getMethod(clazz, method, params));
}
catch (Throwable ex) {
echoError(ex);
}
return null;
}
public static MethodHandle getFinalSetterForFirstOfType(Class<?> clazz, Class<?> fieldType) {
Field field = getFields(clazz).getFirstOfType(fieldType);
if (field == null) {
return null;
}
return getFinalSetter(clazz, field.getName());
}
public static MethodHandle getFinalSetter(Class<?> clazz, String field) {
return getFinalSetter(clazz, field, null);
}
public static MethodHandle getFinalSetter(Class<?> clazz, String field, Class expected) {
Map<String, MethodHandle> map = cachedFieldSetters.computeIfAbsent(clazz, k -> new HashMap<>());
MethodHandle result = map.get(field);
if (result != null) {
return result;
}
Field f = getFields(clazz).get(field);
if (f == null) {
echoError("Create get final setter for unknown field '" + field + "' (for class '" + clazz.getName() + "')");
return null;
}
if (expected != null && f.getType() != expected) {
echoError("[ReflectionHelper] field type mismatch in getFinalSetter: field '" + field + "' in class '" + clazz.getName() + "' returns type '" + f.getType().getCanonicalName() + "' but expected '" + expected.getCanonicalName() + "'");
}
int mod = f.getModifiers();
try {
if (MODIFIERS_FIELD == null) {
validateUnsafe();
boolean isStatic = Modifier.isStatic(mod);
long offset = (long) (isStatic ? UNSAFE_STATIC_FIELD_OFFSET.invoke(f) : UNSAFE_FIELD_OFFSET.invoke(f));
MethodHandle method = UNSAFE_PUT_OBJECT;
if (f.getType().isPrimitive()) {
if (f.getType() == float.class) {
method = UNSAFE_PUT_FLOAT;
}
else if (f.getType() == double.class) {
method = UNSAFE_PUT_DOUBLE;
}
else if (f.getType() == int.class) {
method = UNSAFE_PUT_INT;
}
else if (f.getType() == long.class) {
method = UNSAFE_PUT_LONG;
}
else if (f.getType() == boolean.class) {
method = UNSAFE_PUT_BOOL;
}
else {
echoError("Cannot create a setter for primitive type '" + f.getType().getName() + "'");
return null;
}
}
result = isStatic ? MethodHandles.insertArguments(method, 0, clazz, offset)
: MethodHandles.insertArguments(method, 1, offset);
}
else {
if (Modifier.isFinal(mod)) {
MODIFIERS_FIELD.setInt(f, mod & ~Modifier.FINAL);
}
result = LOOKUP.unreflectSetter(f);
}
}
catch (Throwable ex) {
echoError(ex);
return null;
}
if (result == null) {
return null;
}
cachedFieldSetters.get(clazz).put(field, result);
return result;
}
private static void enableUnsafe() {
if (UNSAFE == null) {
try {
UNSAFE = (Unsafe) getFields(sun.misc.Unsafe.class).get("theUnsafe").get(null);
}
catch (Throwable ex) {
echoError(ex);
}
}
}
private static void validateUnsafe() {
if (!haveLoadedUnsafeMethods) {
haveLoadedUnsafeMethods = true;
enableUnsafe();
UNSAFE_STATIC_FIELD_OFFSET = getMethodHandle(UNSAFE.getClass(), "staticFieldOffset", Field.class).bindTo(UNSAFE);
UNSAFE_FIELD_OFFSET = getMethodHandle(UNSAFE.getClass(), "objectFieldOffset", Field.class).bindTo(UNSAFE);
UNSAFE_PUT_OBJECT = getMethodHandle(UNSAFE.getClass(), "putObject", Object.class, long.class, Object.class).bindTo(UNSAFE);
UNSAFE_PUT_FLOAT = getMethodHandle(UNSAFE.getClass(), "putFloat", Object.class, long.class, float.class).bindTo(UNSAFE);
UNSAFE_PUT_DOUBLE = getMethodHandle(UNSAFE.getClass(), "putDouble", Object.class, long.class, double.class).bindTo(UNSAFE);
UNSAFE_PUT_INT = getMethodHandle(UNSAFE.getClass(), "putInt", Object.class, long.class, int.class).bindTo(UNSAFE);
UNSAFE_PUT_LONG = getMethodHandle(UNSAFE.getClass(), "putLong", Object.class, long.class, long.class).bindTo(UNSAFE);
UNSAFE_PUT_BOOL = getMethodHandle(UNSAFE.getClass(), "putBoolean", Object.class, long.class, boolean.class).bindTo(UNSAFE);
}
}
public static void giveReflectiveAccess(Class<?> targetClass, Class<?> ourClass) {
try {
if (GET_MODULE == null) {
enableUnsafe();
Class<?> module = Class.forName("java.lang.Module");
GET_MODULE = Class.class.getMethod("getModule");
ADD_OPENS = module.getDeclaredMethod("implAddOpens", String.class, module);
UNSAFE.putBoolean(ADD_OPENS, OVERRIDE_OFFSET, true);
}
ADD_OPENS.invoke(GET_MODULE.invoke(targetClass), targetClass.getPackage().getName(), GET_MODULE.invoke(ourClass));
}
catch (Exception ex) {
echoError(ex);
}
}
static {
giveReflectiveAccess(Field.class, ReflectionHelper.class);
MODIFIERS_FIELD = getFields(Field.class).getNoCheck("modifiers");
}
private static final long OVERRIDE_OFFSET = 12; // Field offset of 'override' AKA 'setAccessible'. May change arbitrarily from JDK updates. Required for reflection, so we can't use reflection to read it.
private static Method ADD_OPENS;
private static Method GET_MODULE;
private static MethodHandles.Lookup LOOKUP = MethodHandles.lookup();
private static Field MODIFIERS_FIELD;
private static Unsafe UNSAFE;
private static boolean haveLoadedUnsafeMethods = false;
private static MethodHandle UNSAFE_FIELD_OFFSET, UNSAFE_PUT_OBJECT, UNSAFE_PUT_FLOAT, UNSAFE_PUT_DOUBLE, UNSAFE_PUT_INT, UNSAFE_PUT_LONG, UNSAFE_PUT_BOOL, UNSAFE_STATIC_FIELD_OFFSET;
}