104 lines
3.8 KiB
Java
104 lines
3.8 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.bind;
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import com.google.gson.Gson;
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import com.google.gson.TypeAdapter;
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import com.google.gson.reflect.TypeToken;
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import com.google.gson.stream.JsonReader;
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import com.google.gson.stream.JsonWriter;
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import java.io.IOException;
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import java.lang.reflect.Type;
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import java.lang.reflect.TypeVariable;
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final class TypeAdapterRuntimeTypeWrapper<T> extends TypeAdapter<T> {
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private final Gson context;
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private final TypeAdapter<T> delegate;
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private final Type type;
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TypeAdapterRuntimeTypeWrapper(Gson context, TypeAdapter<T> delegate, Type type) {
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this.context = context;
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this.delegate = delegate;
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this.type = type;
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}
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@Override
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public T read(JsonReader in) throws IOException {
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return delegate.read(in);
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}
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@Override
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public void write(JsonWriter out, T value) throws IOException {
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// Order of preference for choosing type adapters
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// First preference: a type adapter registered for the runtime type
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// Second preference: a type adapter registered for the declared type
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// Third preference: reflective type adapter for the runtime type
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// (if it is a subclass of the declared type)
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// Fourth preference: reflective type adapter for the declared type
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TypeAdapter<T> chosen = delegate;
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Type runtimeType = getRuntimeTypeIfMoreSpecific(type, value);
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if (runtimeType != type) {
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@SuppressWarnings("unchecked")
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TypeAdapter<T> runtimeTypeAdapter =
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(TypeAdapter<T>) context.getAdapter(TypeToken.get(runtimeType));
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// For backward compatibility only check ReflectiveTypeAdapterFactory.Adapter here but not any
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// other wrapping adapters, see
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// https://github.com/google/gson/pull/1787#issuecomment-1222175189
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if (!(runtimeTypeAdapter instanceof ReflectiveTypeAdapterFactory.Adapter)) {
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// The user registered a type adapter for the runtime type, so we will use that
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chosen = runtimeTypeAdapter;
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} else if (!isReflective(delegate)) {
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// The user registered a type adapter for Base class, so we prefer it over the
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// reflective type adapter for the runtime type
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chosen = delegate;
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} else {
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// Use the type adapter for runtime type
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chosen = runtimeTypeAdapter;
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}
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}
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chosen.write(out, value);
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}
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/**
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* Returns whether the type adapter uses reflection.
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*
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* @param typeAdapter the type adapter to check.
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*/
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private static boolean isReflective(TypeAdapter<?> typeAdapter) {
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// Run this in loop in case multiple delegating adapters are nested
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while (typeAdapter instanceof SerializationDelegatingTypeAdapter) {
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TypeAdapter<?> delegate =
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((SerializationDelegatingTypeAdapter<?>) typeAdapter).getSerializationDelegate();
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// Break if adapter does not delegate serialization
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if (delegate == typeAdapter) {
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break;
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}
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typeAdapter = delegate;
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}
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return typeAdapter instanceof ReflectiveTypeAdapterFactory.Adapter;
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}
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/** Finds a compatible runtime type if it is more specific */
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private static Type getRuntimeTypeIfMoreSpecific(Type type, Object value) {
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if (value != null && (type instanceof Class<?> || type instanceof TypeVariable<?>)) {
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type = value.getClass();
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}
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return type;
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}
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}
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