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/*
* Copyright (c) 2019, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package com.oracle.svm.util;
import java.lang.invoke.MethodHandles;
import java.lang.invoke.VarHandle;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
* This class contains utility methods for commonly used reflection functionality. Note that lookups
* will not work on JDK 17 in cases when the field/method is filtered. See
* jdk.internal.reflect.Reflection#fieldFilterMap for more information or
* com.oracle.svm.hosted.ModuleLayerFeature for an example of a workaround in such cases.
*/
public final class ReflectionUtil {
@SuppressWarnings("serial")
public static final class ReflectionUtilError extends Error {
private ReflectionUtilError(Throwable cause) {
super(cause);
}
}
private ReflectionUtil() {
}
/**
* Ensure that this class is allowed to call setAccessible for an element of the provided
* declaring class.
*/
private static void openModule(Class declaringClass) {
ModuleSupport.accessModuleByClass(ModuleSupport.Access.OPEN, ReflectionUtil.class, declaringClass);
}
public static Class lookupClass(boolean optional, String className) {
try {
return Class.forName(className, false, ReflectionUtil.class.getClassLoader());
} catch (ClassNotFoundException ex) {
if (optional) {
return null;
}
throw new ReflectionUtilError(ex);
}
}
public static Method lookupMethod(Class declaringClass, String methodName, Class... parameterTypes) {
return lookupMethod(false, declaringClass, methodName, parameterTypes);
}
public static Method lookupMethod(boolean optional, Class declaringClass, String methodName, Class... parameterTypes) {
try {
Method result = declaringClass.getDeclaredMethod(methodName, parameterTypes);
openModule(declaringClass);
result.setAccessible(true);
return result;
} catch (ReflectiveOperationException ex) {
if (optional) {
return null;
}
throw new ReflectionUtilError(ex);
}
}
public static Method lookupPublicMethodInClassHierarchy(Class clazz, String methodName, Class... parameterTypes) {
return lookupPublicMethodInClassHierarchy(false, clazz, methodName, parameterTypes);
}
public static Method lookupPublicMethodInClassHierarchy(boolean optional, Class clazz, String methodName, Class... parameterTypes) {
try {
Method result = clazz.getMethod(methodName, parameterTypes);
openModule(result.getDeclaringClass());
result.setAccessible(true);
return result;
} catch (ReflectiveOperationException ex) {
if (optional) {
return null;
}
throw new ReflectionUtilError(ex);
}
}
public static Constructor lookupConstructor(Class declaringClass, Class... parameterTypes) {
return lookupConstructor(false, declaringClass, parameterTypes);
}
public static Constructor lookupConstructor(boolean optional, Class declaringClass, Class... parameterTypes) {
try {
Constructor result = declaringClass.getDeclaredConstructor(parameterTypes);
openModule(declaringClass);
result.setAccessible(true);
return result;
} catch (ReflectiveOperationException ex) {
if (optional) {
return null;
}
throw new ReflectionUtilError(ex);
}
}
/**
* Invokes the provided method, and unwraps a possible {@link InvocationTargetException} so that
* it appears as if the method had been invoked directly without the use of reflection.
*/
@SuppressWarnings("unchecked")
public static T invokeMethod(Method method, Object receiver, Object... arguments) {
try {
method.setAccessible(true);
return (T) method.invoke(receiver, arguments);
} catch (InvocationTargetException ex) {
Throwable cause = ex.getCause();
if (cause != null) {
throw rethrow(cause);
}
throw new ReflectionUtilError(ex);
} catch (ReflectiveOperationException ex) {
throw new ReflectionUtilError(ex);
}
}
@SuppressWarnings("unchecked")
private static RuntimeException rethrow(Throwable ex) throws E {
throw (E) ex;
}
public static T newInstance(Class declaringClass) {
try {
return lookupConstructor(declaringClass).newInstance();
} catch (ReflectiveOperationException ex) {
throw new ReflectionUtilError(ex);
}
}
public static T newInstance(Constructor constructor, Object... initArgs) {
try {
return constructor.newInstance(initArgs);
} catch (ReflectiveOperationException ex) {
throw new ReflectionUtilError(ex);
}
}
public static VarHandle unreflectField(Class declaringClass, String fieldName, MethodHandles.Lookup lookup) {
try {
Field field = ReflectionUtil.lookupField(declaringClass, fieldName);
MethodHandles.Lookup privateLookup = MethodHandles.privateLookupIn(declaringClass, lookup);
return privateLookup.unreflectVarHandle(field);
} catch (IllegalAccessException ex) {
throw new ReflectionUtilError(ex);
}
}
public static Field lookupField(Class declaringClass, String fieldName) {
return lookupField(false, declaringClass, fieldName);
}
private static final Method fieldGetDeclaredFields0 = ReflectionUtil.lookupMethod(Class.class, "getDeclaredFields0", boolean.class);
public static Field lookupField(boolean optional, Class declaringClass, String fieldName) {
try {
Field result = declaringClass.getDeclaredField(fieldName);
openModule(declaringClass);
result.setAccessible(true);
return result;
} catch (ReflectiveOperationException ex) {
/* Try to get hidden field */
try {
Field[] allFields = (Field[]) fieldGetDeclaredFields0.invoke(declaringClass, false);
for (Field field : allFields) {
if (field.getName().equals(fieldName)) {
openModule(declaringClass);
field.setAccessible(true);
return field;
}
}
} catch (ReflectiveOperationException e) {
// ignore
}
if (optional) {
return null;
}
throw new ReflectionUtilError(ex);
}
}
@SuppressWarnings("unchecked")
public static T readField(Class declaringClass, String fieldName, Object receiver) {
try {
return (T) lookupField(declaringClass, fieldName).get(receiver);
} catch (ReflectiveOperationException ex) {
throw new ReflectionUtilError(ex);
}
}
public static T readStaticField(Class declaringClass, String fieldName) {
return readField(declaringClass, fieldName, null);
}
public static void writeField(Class declaringClass, String fieldName, Object receiver, Object value) {
try {
lookupField(declaringClass, fieldName).set(receiver, value);
} catch (ReflectiveOperationException ex) {
throw new ReflectionUtilError(ex);
}
}
public static void writeStaticField(Class declaringClass, String fieldName, Object value) {
writeField(declaringClass, fieldName, null, value);
}
}