forked from google/gson
/
ReflectionAccessor.java
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/
ReflectionAccessor.java
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/*
* Copyright (C) 2017 The Gson authors
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.gson.internal.reflect;
import java.lang.invoke.MethodHandle;
import java.lang.invoke.MethodHandles;
import java.lang.reflect.AccessibleObject;
import java.lang.reflect.Method;
/**
* Provides a replacement for {@link AccessibleObject#setAccessible(boolean)}, which may be used to
* avoid reflective access issues appeared in Java 9, like {@link java.lang.reflect.InaccessibleObjectException}
* thrown or warnings like
* <pre>
* WARNING: An illegal reflective access operation has occurred
* WARNING: Illegal reflective access by ...
* </pre>
* <p/>
* Works both for Java 9 and earlier Java versions.
*/
public final class ReflectionAccessor {
// the singleton instance, use getInstance() to obtain
private static final ReflectionAccessor instance = new ReflectionAccessor();
private final MethodHandle trySetAccessible = getTrySetAccessibleMethod();
/**
* Does the same as {@code ao.setAccessible(true)}, but never throws
* {@link java.lang.reflect.InaccessibleObjectException}
* @return <code>true</code> if the object is accessible.
*/
public boolean makeAccessible(AccessibleObject ao) {
try {
if (trySetAccessible != null) {
return (boolean) trySetAccessible.invoke(ao);
} else if (!ao.isAccessible()) { // if trySetAccessible() is not available then neither is canAccess()
ao.setAccessible(true);
}
return true;
} catch (final Throwable error) {
return false;
}
}
/**
* Obtains a {@link ReflectionAccessor} instance.
* <p>
* You may need one if a reflective operation in your code throws {@link java.lang.reflect.InaccessibleObjectException}.
* In such a case, use {@link ReflectionAccessor#makeAccessible(AccessibleObject)} on a field, method or constructor
* (instead of basic {@link AccessibleObject#setAccessible(boolean)}).
*/
public static ReflectionAccessor getInstance() {
return instance;
}
private static MethodHandle getTrySetAccessibleMethod() {
try {
Method method = AccessibleObject.class.getMethod("trySetAccessible");
return MethodHandles.publicLookup().unreflect(method);
} catch (Exception e) {
return null;
}
}
}