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 * Copyright (c) 2017, 2017, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * 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.
 *
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package com.oracle.svm.thirdparty.gson;

import org.graalvm.nativeimage.hosted.Feature;
import org.graalvm.nativeimage.hosted.RuntimeReflection;

import com.oracle.svm.core.annotate.AutomaticFeature;
import com.oracle.svm.core.util.VMError;

Support for the Gson library on SubstrateVM.
 Gson uses reflection to instantiate data classes and write properties. All such data classes need to be registered manually by the user using the runtime reflection
support of Substrate VM. It is not feasible to automatically detect all necessary classes. 
 This feature registers parts of Unsafe as reflectively accessible. Gson uses it internally to instantiate classes that do not have a no-argument constructor. /**
 * Support for the Gson library on SubstrateVM.
 * <p>
 * Gson uses reflection to instantiate data classes and write properties. All such data classes need
 * to be registered manually by the user using the {@link RuntimeReflection runtime reflection
 * support} of Substrate VM. It is not feasible to automatically detect all necessary classes.
 * <p>
 * This feature registers parts of {@link sun.misc.Unsafe} as reflectively accessible. Gson uses it
 * internally to instantiate classes that do not have a no-argument constructor.
 */
@AutomaticFeature
public final class GsonFeature implements Feature {

    @Override
    public boolean isInConfiguration(IsInConfigurationAccess access) {
        return access.findClassByName("com.google.gson.Gson") != null;
    }

    @Override
    public void beforeAnalysis(BeforeAnalysisAccess access) {
        try {
            /* Reflection usage in com.google.gson.internal.UnsafeAllocator.create(). */
            RuntimeReflection.register(sun.misc.Unsafe.class);
            RuntimeReflection.register(sun.misc.Unsafe.class.getDeclaredField("theUnsafe"));
            RuntimeReflection.register(sun.misc.Unsafe.class.getDeclaredMethod("allocateInstance", Class.class));
        } catch (NoSuchFieldException | NoSuchMethodException ex) {
            throw VMError.shouldNotReachHere(ex);
        }
    }
}