464 lines
17 KiB
Java
464 lines
17 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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/** Returns a function that can construct an instance of a requested type. */
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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(
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Map<Type, InstanceCreator<?>> instanceCreators,
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boolean useJdkUnsafe,
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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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/**
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* Check if the class can be instantiated by Unsafe allocator. If the instance has interface or
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* abstract modifiers return an exception message.
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*
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* @param c instance of the class to be checked
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* @return if instantiable {@code null}, else a non-{@code null} exception message
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*/
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static String checkInstantiable(Class<?> c) {
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int modifiers = c.getModifiers();
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if (Modifier.isInterface(modifiers)) {
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return "Interfaces can't be instantiated! Register an InstanceCreator"
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+ " or a TypeAdapter for this type. Interface name: "
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+ c.getName();
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}
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if (Modifier.isAbstract(modifiers)) {
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// R8 performs aggressive optimizations where it removes the default constructor of a class
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// and makes the class `abstract`; check for that here explicitly
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/*
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* Note: Ideally should only show this R8-specific message when it is clear that R8 was
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* used (e.g. when `c.getDeclaredConstructors().length == 0`), but on Android where this
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* issue with R8 occurs most, R8 seems to keep some constructors for some reason while
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* still making the class abstract
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*/
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return "Abstract classes can't be instantiated! Adjust the R8 configuration or register"
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+ " an InstanceCreator or a TypeAdapter for this type. Class name: "
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+ c.getName()
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+ "\nSee "
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+ TroubleshootingGuide.createUrl("r8-abstract-class");
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}
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return null;
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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
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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 = (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
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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 =
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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 = checkInstantiable(rawType);
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if (exceptionMessage != null) {
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return new ObjectConstructor<T>() {
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@Override
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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 =
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"Unable to create instance of "
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+ rawType
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+ "; ReflectionAccessFilter does not permit using reflection or Unsafe. Register an"
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+ " InstanceCreator or a TypeAdapter for this type or adjust the access filter to"
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+ " allow using reflection.";
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return new ObjectConstructor<T>() {
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@Override
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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
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* constructor.
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*/
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private static <T> ObjectConstructor<T> newSpecialCollectionConstructor(
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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
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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
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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(
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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 =
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filterResult == FilterResult.ALLOW
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|| (ReflectionAccessFilterHelper.canAccess(constructor, null)
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// Be a bit more lenient here for BLOCK_ALL; if constructor is accessible and public
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// then allow calling it
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&& (filterResult != FilterResult.BLOCK_ALL
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|| Modifier.isPublic(constructor.getModifiers())));
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if (!canAccess) {
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final String message =
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"Unable to invoke no-args constructor of "
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+ rawType
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+ ";"
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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
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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
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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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}
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// Note: InstantiationException should be impossible because check at start of method made
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// sure that class is not abstract
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catch (InstantiationException e) {
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throw new RuntimeException(
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"Failed to invoke constructor '"
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+ ReflectionHelper.constructorToString(constructor)
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+ "' with no args",
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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(
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"Failed to invoke constructor '"
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+ ReflectionHelper.constructorToString(constructor)
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+ "' with no args",
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e.getCause());
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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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/** Constructors for common interface types like Map and List and their subtypes. */
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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
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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
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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
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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
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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
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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
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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
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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
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&& !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
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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
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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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@Override
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public T construct() {
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try {
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@SuppressWarnings("unchecked")
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T newInstance = (T) UnsafeAllocator.INSTANCE.newInstance(rawType);
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return newInstance;
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} catch (Exception e) {
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throw new RuntimeException(
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("Unable to create instance of "
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+ rawType
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+ ". Registering an InstanceCreator or a TypeAdapter for this type, or adding a"
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+ " no-args constructor may fix this problem."),
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e);
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}
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}
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};
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} else {
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String exceptionMessage =
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"Unable to create instance of "
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+ rawType
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+ "; usage of JDK Unsafe is disabled. Registering an InstanceCreator or a TypeAdapter"
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+ " for this type, adding a no-args constructor, or enabling usage of JDK Unsafe may"
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+ " fix this problem.";
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// Check if R8 removed all constructors
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if (rawType.getDeclaredConstructors().length == 0) {
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// R8 with Unsafe disabled might not be common enough to warrant a separate Troubleshooting
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// Guide entry
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exceptionMessage +=
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" Or adjust your R8 configuration to keep the no-args constructor of the class.";
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}
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// Explicit final variable to allow usage in the anonymous class below
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final String exceptionMessageF = exceptionMessage;
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return new ObjectConstructor<T>() {
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@Override
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public T construct() {
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throw new JsonIOException(exceptionMessageF);
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}
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};
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}
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}
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@Override
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public String toString() {
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return instanceCreators.toString();
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}
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}
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