io.datakernel.serializer.GsonSubclassesAdapter.java Source code

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Here is the source code for io.datakernel.serializer.GsonSubclassesAdapter.java

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/*
 * Copyright (C) 2015 SoftIndex LLC.
 *
 * 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 io.datakernel.serializer;

import com.google.common.collect.ImmutableBiMap;
import com.google.common.collect.ImmutableMap;
import com.google.gson.*;

import java.lang.reflect.Constructor;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Modifier;
import java.lang.reflect.Type;
import java.util.HashMap;
import java.util.Map;

public final class GsonSubclassesAdapter<T> implements JsonSerializer<T>, JsonDeserializer<T> {
    private final ImmutableBiMap<String, Class<? extends T>> classTags;
    private final ImmutableMap<String, InstanceCreator<T>> classCreators;
    private final ImmutableBiMap<String, Class<? extends T>> subclassNames;
    private final String subclassField;

    public GsonSubclassesAdapter(Map<String, Class<? extends T>> classTags,
            Map<String, InstanceCreator<T>> classCreators, String subclassField,
            Map<String, Class<? extends T>> subclassNames) {
        this.classTags = ImmutableBiMap.copyOf(classTags);
        this.classCreators = ImmutableMap.copyOf(classCreators);
        this.subclassField = subclassField;
        this.subclassNames = ImmutableBiMap.copyOf(subclassNames);
    }

    public static class Builder<T> {
        private final Map<String, Class<? extends T>> classTags = new HashMap<>();
        private final Map<String, InstanceCreator<T>> classCreators = new HashMap<>();
        private final Map<String, Class<? extends T>> subclassNames = new HashMap<>();
        private String subclassField = "_type";

        public Builder<T> classTag(String classTag, Class<? extends T> type, InstanceCreator<T> instanceCreator) {
            this.classTags.put(classTag, type);
            this.classCreators.put(classTag, instanceCreator);
            return this;
        }

        public Builder<T> classTag(String classTag, Class<? extends T> type) {
            this.classTags.put(classTag, type);
            return this;
        }

        public Builder<T> subclassField(String subclassField) {
            this.subclassField = subclassField;
            return this;
        }

        public Builder<T> subclass(String subclassName, Class<? extends T> subclass) {
            this.subclassNames.put(subclassName, subclass);
            return this;
        }

        public GsonSubclassesAdapter<T> build() {
            return new GsonSubclassesAdapter<>(classTags, classCreators, subclassField, subclassNames);
        }
    }

    public static <T> Builder<T> builder() {
        return new Builder<>();
    }

    private static Object newInstance(Class<?> type) throws InstantiationException, IllegalAccessException,
            NoSuchMethodException, InvocationTargetException {
        boolean isStatic = (type.getModifiers() & Modifier.STATIC) != 0;
        Class<?> enclosingClass = type.getEnclosingClass();
        if (isStatic || enclosingClass == null) {
            Constructor<?> ctor = type.getDeclaredConstructor();
            ctor.setAccessible(true);
            return ctor.newInstance();
        }
        Object enclosingInstance = newInstance(enclosingClass);
        Constructor<?> ctor = type.getDeclaredConstructor(enclosingClass);
        ctor.setAccessible(true);
        return ctor.newInstance(enclosingInstance);
    }

    @SuppressWarnings("unchecked")
    @Override
    public JsonElement serialize(T src, Type typeOfSrc, JsonSerializationContext context) {
        Class<? extends T> aClass = (Class<? extends T>) src.getClass();
        String classTag = classTags.inverse().get(aClass);
        if (classTag != null) {
            return new JsonPrimitive(classTag);
        }
        String subclassName = subclassNames.inverse().get(aClass);
        if (subclassName != null) {
            JsonObject result = new JsonObject();
            result.addProperty(subclassField, subclassName);
            JsonObject element = (JsonObject) context.serialize(src, src.getClass());
            for (Map.Entry<String, JsonElement> entry : element.entrySet()) {
                result.add(entry.getKey(), entry.getValue());
            }
            return result;
        }
        return new JsonPrimitive(src.getClass().getName());
    }

    @SuppressWarnings("unchecked")
    @Override
    public T deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
        if (json.isJsonPrimitive()) {
            if (!((JsonPrimitive) json).isString()) {
                throw new JsonParseException("Inner class name is expected");
            }
            String className = json.getAsString();
            InstanceCreator<T> creator = classCreators.get(className);
            if (creator != null) {
                return creator.createInstance(typeOfT);
            }
            try {
                Class<?> aClass = classTags.get(className);
                if (aClass == null) {
                    aClass = Class.forName(className);
                }
                return (T) newInstance(aClass);
            } catch (InvocationTargetException | ClassNotFoundException | InstantiationException
                    | IllegalAccessException | NoSuchMethodException e) {
                throw new JsonParseException(e);
            }
        }
        JsonObject object = json.getAsJsonObject();
        String subclassName = object.get(subclassField).getAsString();
        return context.deserialize(json, subclassNames.get(subclassName));
    }
}