/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.dubbo.common.serialize.kryo;

import org.apache.dubbo.common.logger.Logger;
import org.apache.dubbo.common.logger.LoggerFactory;
import org.apache.dubbo.common.utils.ReflectUtils;

import com.esotericsoftware.kryo.Kryo;
import com.esotericsoftware.kryo.Serializer;
import com.esotericsoftware.kryo.serializers.JavaSerializer;

public class CompatibleKryo extends Kryo {

    private static final Logger logger = LoggerFactory.getLogger(CompatibleKryo.class);

    @Override
    public Serializer getDefaultSerializer(Class type) {
        if (type == null) {
            throw new IllegalArgumentException("type cannot be null.");
        }

        /**
         * Kryo requires every class to provide a zero argument constructor. For any class does not match this condition, kryo have two ways:
         * 1. Use JavaSerializer,
         * 2. Set 'kryo.setInstantiatorStrategy(new DefaultInstantiatorStrategy(new StdInstantiatorStrategy()));', StdInstantiatorStrategy can generate an instance bypassing the constructor.
         *
         * In practice, it's not possible for Dubbo users to register kryo Serializer for every customized class. So in most cases, customized classes with/without zero argument constructor will
         * default to the default serializer.
         * It is the responsibility of kryo to handle with every standard jdk classes, so we will just escape these classes.
         */
        if (!ReflectUtils.isJdk(type) && !type.isArray() && !type.isEnum() && !ReflectUtils.checkZeroArgConstructor(type)) {
            if (logger.isWarnEnabled()) {
                logger.warn(type + " has no zero-arg constructor and this will affect the serialization performance");
            }
            return new JavaSerializer();
        }
        return super.getDefaultSerializer(type);
    }
}
