374 lines
14 KiB
Java
374 lines
14 KiB
Java
/*
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* Copyright (C) 2011 Google Inc.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.google.gson.internal;
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import com.google.gson.InstanceCreator;
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import com.google.gson.JsonIOException;
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import com.google.gson.ReflectionAccessFilter;
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import com.google.gson.ReflectionAccessFilter.FilterResult;
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import com.google.gson.internal.reflect.ReflectionHelper;
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import com.google.gson.reflect.TypeToken;
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import java.lang.reflect.Constructor;
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import java.lang.reflect.InvocationTargetException;
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import java.lang.reflect.Modifier;
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import java.lang.reflect.ParameterizedType;
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import java.lang.reflect.Type;
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import java.util.ArrayDeque;
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import java.util.ArrayList;
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import java.util.Collection;
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import java.util.EnumMap;
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import java.util.EnumSet;
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import java.util.LinkedHashMap;
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import java.util.LinkedHashSet;
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import java.util.List;
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import java.util.Map;
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import java.util.Queue;
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import java.util.Set;
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import java.util.SortedMap;
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import java.util.SortedSet;
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import java.util.TreeMap;
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import java.util.TreeSet;
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import java.util.concurrent.ConcurrentHashMap;
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import java.util.concurrent.ConcurrentMap;
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import java.util.concurrent.ConcurrentNavigableMap;
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import java.util.concurrent.ConcurrentSkipListMap;
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/**
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* Returns a function that can construct an instance of a requested type.
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*/
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public final class ConstructorConstructor {
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private final Map<Type, InstanceCreator<?>> instanceCreators;
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private final boolean useJdkUnsafe;
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private final List<ReflectionAccessFilter> reflectionFilters;
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public ConstructorConstructor(Map<Type, InstanceCreator<?>> instanceCreators, boolean useJdkUnsafe, List<ReflectionAccessFilter> reflectionFilters) {
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this.instanceCreators = instanceCreators;
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this.useJdkUnsafe = useJdkUnsafe;
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this.reflectionFilters = reflectionFilters;
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}
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public <T> ObjectConstructor<T> get(TypeToken<T> typeToken) {
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final Type type = typeToken.getType();
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final Class<? super T> rawType = typeToken.getRawType();
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// first try an instance creator
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@SuppressWarnings("unchecked") // types must agree
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final InstanceCreator<T> typeCreator = (InstanceCreator<T>) instanceCreators.get(type);
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if (typeCreator != null) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return typeCreator.createInstance(type);
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}
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};
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}
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// Next try raw type match for instance creators
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@SuppressWarnings("unchecked") // types must agree
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final InstanceCreator<T> rawTypeCreator =
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(InstanceCreator<T>) instanceCreators.get(rawType);
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if (rawTypeCreator != null) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return rawTypeCreator.createInstance(type);
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}
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};
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}
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// First consider special constructors before checking for no-args constructors
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// below to avoid matching internal no-args constructors which might be added in
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// future JDK versions
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ObjectConstructor<T> specialConstructor = newSpecialCollectionConstructor(type, rawType);
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if (specialConstructor != null) {
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return specialConstructor;
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}
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FilterResult filterResult = ReflectionAccessFilterHelper.getFilterResult(reflectionFilters, rawType);
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ObjectConstructor<T> defaultConstructor = newDefaultConstructor(rawType, filterResult);
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if (defaultConstructor != null) {
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return defaultConstructor;
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}
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ObjectConstructor<T> defaultImplementation = newDefaultImplementationConstructor(type, rawType);
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if (defaultImplementation != null) {
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return defaultImplementation;
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}
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// Check whether type is instantiable; otherwise ReflectionAccessFilter recommendation
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// of adjusting filter suggested below is irrelevant since it would not solve the problem
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final String exceptionMessage = UnsafeAllocator.checkInstantiable(rawType);
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if (exceptionMessage != null) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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throw new JsonIOException(exceptionMessage);
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}
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};
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}
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// Consider usage of Unsafe as reflection, so don't use if BLOCK_ALL
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// Additionally, since it is not calling any constructor at all, don't use if BLOCK_INACCESSIBLE
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if (filterResult == FilterResult.ALLOW) {
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// finally try unsafe
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return newUnsafeAllocator(rawType);
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} else {
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final String message = "Unable to create instance of " + rawType + "; ReflectionAccessFilter "
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+ "does not permit using reflection or Unsafe. Register an InstanceCreator or a TypeAdapter "
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+ "for this type or adjust the access filter to allow using reflection.";
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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throw new JsonIOException(message);
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}
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};
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}
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}
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/**
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* Creates constructors for special JDK collection types which do not have a public no-args constructor.
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*/
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private static <T> ObjectConstructor<T> newSpecialCollectionConstructor(final Type type, Class<? super T> rawType) {
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if (EnumSet.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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if (type instanceof ParameterizedType) {
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Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
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if (elementType instanceof Class) {
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@SuppressWarnings({"unchecked", "rawtypes"})
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T set = (T) EnumSet.noneOf((Class)elementType);
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return set;
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} else {
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throw new JsonIOException("Invalid EnumSet type: " + type.toString());
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}
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} else {
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throw new JsonIOException("Invalid EnumSet type: " + type.toString());
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}
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}
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};
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}
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// Only support creation of EnumMap, but not of custom subtypes; for them type parameters
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// and constructor parameter might have completely different meaning
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else if (rawType == EnumMap.class) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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if (type instanceof ParameterizedType) {
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Type elementType = ((ParameterizedType) type).getActualTypeArguments()[0];
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if (elementType instanceof Class) {
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@SuppressWarnings({"unchecked", "rawtypes"})
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T map = (T) new EnumMap((Class) elementType);
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return map;
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} else {
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throw new JsonIOException("Invalid EnumMap type: " + type.toString());
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}
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} else {
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throw new JsonIOException("Invalid EnumMap type: " + type.toString());
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}
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}
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};
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}
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return null;
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}
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private static <T> ObjectConstructor<T> newDefaultConstructor(Class<? super T> rawType, FilterResult filterResult) {
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// Cannot invoke constructor of abstract class
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if (Modifier.isAbstract(rawType.getModifiers())) {
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return null;
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}
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final Constructor<? super T> constructor;
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try {
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constructor = rawType.getDeclaredConstructor();
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} catch (NoSuchMethodException e) {
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return null;
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}
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boolean canAccess = filterResult == FilterResult.ALLOW || (ReflectionAccessFilterHelper.canAccess(constructor, null)
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// Be a bit more lenient here for BLOCK_ALL; if constructor is accessible and public then allow calling it
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&& (filterResult != FilterResult.BLOCK_ALL || Modifier.isPublic(constructor.getModifiers())));
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if (!canAccess) {
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final String message = "Unable to invoke no-args constructor of " + rawType + "; "
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+ "constructor is not accessible and ReflectionAccessFilter does not permit making "
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+ "it accessible. Register an InstanceCreator or a TypeAdapter for this type, change "
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+ "the visibility of the constructor or adjust the access filter.";
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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throw new JsonIOException(message);
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}
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};
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}
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// Only try to make accessible if allowed; in all other cases checks above should
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// have verified that constructor is accessible
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if (filterResult == FilterResult.ALLOW) {
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final String exceptionMessage = ReflectionHelper.tryMakeAccessible(constructor);
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if (exceptionMessage != null) {
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/*
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* Create ObjectConstructor which throws exception.
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* This keeps backward compatibility (compared to returning `null` which
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* would then choose another way of creating object).
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* And it supports types which are only serialized but not deserialized
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* (compared to directly throwing exception here), e.g. when runtime type
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* of object is inaccessible, but compile-time type is accessible.
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*/
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return new ObjectConstructor<T>() {
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@Override
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public T construct() {
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// New exception is created every time to avoid keeping reference
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// to exception with potentially long stack trace, causing a
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// memory leak
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throw new JsonIOException(exceptionMessage);
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}
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};
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}
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}
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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try {
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@SuppressWarnings("unchecked") // T is the same raw type as is requested
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T newInstance = (T) constructor.newInstance();
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return newInstance;
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} catch (InstantiationException e) {
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// TODO: JsonParseException ?
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throw new RuntimeException("Failed to invoke " + constructor + " with no args", e);
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} catch (InvocationTargetException e) {
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// TODO: don't wrap if cause is unchecked!
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// TODO: JsonParseException ?
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throw new RuntimeException("Failed to invoke " + constructor + " with no args",
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e.getTargetException());
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} catch (IllegalAccessException e) {
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throw ReflectionHelper.createExceptionForUnexpectedIllegalAccess(e);
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}
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}
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};
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}
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/**
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* Constructors for common interface types like Map and List and their
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* subtypes.
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*/
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@SuppressWarnings("unchecked") // use runtime checks to guarantee that 'T' is what it is
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private static <T> ObjectConstructor<T> newDefaultImplementationConstructor(
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final Type type, Class<? super T> rawType) {
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/*
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* IMPORTANT: Must only create instances for classes with public no-args constructor.
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* For classes with special constructors / factory methods (e.g. EnumSet)
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* `newSpecialCollectionConstructor` defined above must be used, to avoid no-args
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* constructor check (which is called before this method) detecting internal no-args
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* constructors which might be added in a future JDK version
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*/
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if (Collection.class.isAssignableFrom(rawType)) {
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if (SortedSet.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new TreeSet<>();
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}
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};
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} else if (Set.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new LinkedHashSet<>();
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}
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};
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} else if (Queue.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new ArrayDeque<>();
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}
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};
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} else {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new ArrayList<>();
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}
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};
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}
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}
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if (Map.class.isAssignableFrom(rawType)) {
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if (ConcurrentNavigableMap.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new ConcurrentSkipListMap<>();
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}
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};
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} else if (ConcurrentMap.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new ConcurrentHashMap<>();
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}
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};
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} else if (SortedMap.class.isAssignableFrom(rawType)) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new TreeMap<>();
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}
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};
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} else if (type instanceof ParameterizedType && !(String.class.isAssignableFrom(
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TypeToken.get(((ParameterizedType) type).getActualTypeArguments()[0]).getRawType()))) {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new LinkedHashMap<>();
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}
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};
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} else {
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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return (T) new LinkedTreeMap<>();
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}
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};
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}
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}
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return null;
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}
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private <T> ObjectConstructor<T> newUnsafeAllocator(final Class<? super T> rawType) {
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if (useJdkUnsafe) {
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return new ObjectConstructor<T>() {
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private final UnsafeAllocator unsafeAllocator = UnsafeAllocator.create();
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@Override public T construct() {
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try {
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@SuppressWarnings("unchecked")
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T newInstance = (T) unsafeAllocator.newInstance(rawType);
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return newInstance;
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} catch (Exception e) {
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throw new RuntimeException(("Unable to create instance of " + rawType + ". "
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+ "Registering an InstanceCreator or a TypeAdapter for this type, or adding a no-args "
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+ "constructor may fix this problem."), e);
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}
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}
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};
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} else {
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final String exceptionMessage = "Unable to create instance of " + rawType + "; usage of JDK Unsafe "
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+ "is disabled. Registering an InstanceCreator or a TypeAdapter for this type, adding a no-args "
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+ "constructor, or enabling usage of JDK Unsafe may fix this problem.";
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return new ObjectConstructor<T>() {
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@Override public T construct() {
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throw new JsonIOException(exceptionMessage);
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}
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};
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}
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}
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@Override public String toString() {
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return instanceCreators.toString();
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}
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}
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