com.tinease.tools.json.TypeAdapterRuntimeTypeWrapper.java Source code

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Here is the source code for com.tinease.tools.json.TypeAdapterRuntimeTypeWrapper.java

Source

package com.tinease.tools.json;

import com.google.gson.TypeAdapter;
import com.google.gson.internal.bind.ReflectiveTypeAdapterFactory;
/*
 * 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.
 */
import com.google.gson.Gson;
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);
    }

    @SuppressWarnings({ "rawtypes", "unchecked" })
    @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 chosen = delegate;
        Type runtimeType = getRuntimeTypeIfMoreSpecific(type, value);
        if (runtimeType != type) {
            TypeAdapter runtimeTypeAdapter = context.getAdapter(TypeToken.get(runtimeType));
            if (!(runtimeTypeAdapter instanceof ReflectiveTypeAdapterFactory.Adapter)) {
                // The user registered a type adapter for the runtime type, so we will use that
                chosen = runtimeTypeAdapter;
            } else if (!(delegate instanceof ReflectiveTypeAdapterFactory.Adapter)) {
                // 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);
    }

    /**
     * Finds a compatible runtime type if it is more specific
     */
    private Type getRuntimeTypeIfMoreSpecific(Type type, Object value) {
        if (value != null
                && (type == Object.class || type instanceof TypeVariable<?> || type instanceof Class<?>)) {
            type = value.getClass();
        }
        return type;
    }
}