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/*
* Copyright (C) 2011 Google Inc.
*
* 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.bind;
import com.google.gson.Gson;
import com.google.gson.TypeAdapter;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import java.io.IOException;
import java.lang.reflect.Type;
import java.lang.reflect.TypeVariable;
final class TypeAdapterRuntimeTypeWrapper<T> extends TypeAdapter<T> {
private final Gson context;
private final TypeAdapter<T> delegate;
private final Type type;
TypeAdapterRuntimeTypeWrapper(Gson context, TypeAdapter<T> delegate, Type type) {
this.context = context;
this.delegate = delegate;
this.type = type;
}
@Override
public T read(JsonReader in) throws IOException {
return delegate.read(in);
}
@Override
public void write(JsonWriter out, T value) throws IOException {
// Order of preference for choosing type adapters
// First preference: a type adapter registered for the runtime type
// Second preference: a type adapter registered for the declared type
// Third preference: reflective type adapter for the runtime type (if it is a sub class of the declared type)
// Fourth preference: reflective type adapter for the declared type
TypeAdapter<T> chosen = delegate;
Type runtimeType = getRuntimeTypeIfMoreSpecific(type, value);
if (runtimeType != type) {
@SuppressWarnings("unchecked")
TypeAdapter<T> runtimeTypeAdapter = (TypeAdapter<T>) context.getAdapter(TypeToken.get(runtimeType));
// For backward compatibility only check ReflectiveTypeAdapterFactory.Adapter here but not any other
// wrapping adapters, see https://github.com/google/gson/pull/1787#issuecomment-1222175189
if (!(runtimeTypeAdapter instanceof ReflectiveTypeAdapterFactory.Adapter)) {
// The user registered a type adapter for the runtime type, so we will use that
chosen = runtimeTypeAdapter;
} else if (!isReflective(delegate)) {
// The user registered a type adapter for Base class, so we prefer it over the
// reflective type adapter for the runtime type
chosen = delegate;
} else {
// Use the type adapter for runtime type
chosen = runtimeTypeAdapter;
}
}
chosen.write(out, value);
}
/**
* Returns whether the type adapter uses reflection.
*
* @param typeAdapter the type adapter to check.
*/
private static boolean isReflective(TypeAdapter<?> typeAdapter) {
// Run this in loop in case multiple delegating adapters are nested
while (typeAdapter instanceof SerializationDelegatingTypeAdapter) {
TypeAdapter<?> delegate = ((SerializationDelegatingTypeAdapter<?>) typeAdapter).getSerializationDelegate();
// Break if adapter does not delegate serialization
if (delegate == typeAdapter) {
break;
}
typeAdapter = delegate;
}
return typeAdapter instanceof ReflectiveTypeAdapterFactory.Adapter;
}
/**
* Finds a compatible runtime type if it is more specific
*/
private static Type getRuntimeTypeIfMoreSpecific(Type type, Object value) {
if (value != null && (type instanceof Class<?> || type instanceof TypeVariable<?>)) {
type = value.getClass();
}
return type;
}
}
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