Deserialization failing randomly - version 2.02

What steps will reproduce the problem?
1. Create and use same serializer class on both ends of a client server 
application.
2. Serialize the class from one end.
3. Deserialize the class on the other end.

What is the expected output? What do you see instead?

I have noticed the deserialization fails randomly with the following exception, 
even though I created the serializer class with 
kryo.setRegistrationRequired(true) :

com.esotericsoftware.kryo.KryoException: Encountered unregistered class ID: 48
Serialization trace:
command (remoting.Message)
    at com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:517)
    at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:208)
    at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:537)

What version of the Kryo are you using?

Version 2.02

Please provide any additional information below.

First of all let me say that this is an awesome project and really rocks, thank 
you!

As described above I created a MessageConverted class which is capable of 
serializing/deserializing a Message object and I have been careful to use 
kryo.setRegistrationRequired(true) so that I can explicitly catch any classes 
that are not registered. This did help me catch classes that were not 
registered like Arrays.ArrayList. I am using the same converter class on both 
ends of a client server application. The problem I am seeing is that the 
deserialization often fails with the following message:

com.esotericsoftware.kryo.KryoException: Encountered unregistered class ID: 48
Serialization trace:
command (remoting.Message)
    at com.esotericsoftware.kryo.Kryo.readClass(Kryo.java:517)
    at com.esotericsoftware.kryo.serializers.FieldSerializer.read(FieldSerializer.java:208)
    at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:537)

Since I am using the same converter class on both the ends and have explicitly 
set class registration as required, I am not sure why the serialization 
succeeds and deserialization fails with the above exception. Furthermore both 
the server and the client is brand new code that I am writing and so there is 
no question of different versions of the classes running on each end. 

Here is the converter class that I am using:

import java.io.ByteArrayOutputStream;
import java.lang.reflect.Field;
import java.math.BigDecimal;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.HashMap;

import com.esotericsoftware.kryo.Kryo;
import com.esotericsoftware.kryo.Serializer;
import com.esotericsoftware.kryo.io.Input;
import com.esotericsoftware.kryo.io.Output;
import com.esotericsoftware.kryo.serializers.ArraySerializer;
import com.esotericsoftware.kryo.serializers.CompatibleFieldSerializer;

import data.user.User;
import hibernate.LongId;
import model.stockdata.WriteProtectedTicker;
import model.trade.QuoteType;
import model.trade.stock.DirectionSymbol;
import model.trade.stock.Exchange;
import model.trade.stock.Quote;
import model.trade.stock.Quote.HaltIndicatorCode;
import model.trade.stock.Quote.HaltStatusCode;
import model.trade.stock.Quote.QuoteSource;
import model.trade.stock.Ticker;
import remoting.Message;
import remoting.MessageContext;
import remoting.MessageConverter;

/**
 * This class is used to provide extremely compact representation of messages when sent over the wire.
 * <p>
 * 
 * The class internally uses the Kryo java serialization framework (http://code.google.com/p/kryo/).
 * <p>
 * 
 * @author me
 */
public class DefaultMessageConverter implements MessageConverter {
    /**
     * An internal thread local is used to cache the created Kryo instances at a
     * thread local level (Kryo is not thread safe) ...
     */
    private ThreadLocal<Kryo> converters = new ThreadLocal<Kryo>();

    /**
     * This method is used to convert a message into bytes.
     * <p>
     * 
     * @param message
     *            instance of Message that needs to be converted
     * @return a byte array representing the conversion
     * @throws NullPointerException
     *             if passed in message is null
     */
    public byte[] toBytes(Message message) {
        Kryo converter = getConverter();

        ByteArrayOutputStream bos = new ByteArrayOutputStream();
        Output output = new Output(bos);

        converter.writeObject(output, message);

        return output.toBytes();
    }

    /**
     * This method reconstructs the Message from the given bytes.
     * <p>
     * 
     * @param encoded
     *            a byte array representing the serialized message
     * @return the reconstructed Message
     * @throws NullPointerException
     *             if passed in byte array is null
     */
    public Message fromBytes(byte[] encoded) {
        Kryo converter = getConverter();
        Input input = new Input(encoded);

        return converter.readObject(input, Message.class);
    }

    /**
     * This method is used to get the instance of the kryo converter associated with
     * the running thread.
     * <p>
     * 
     * @return a new Kryo instance
     */
    private Kryo getConverter() {
        Kryo kryo = converters.get();
        if (kryo == null) {
            // PLEASE DO NOT CHANGE THE SEQUENCE OF ANY OF THE CLASSES
            // WHILE ADDING NEW CLASSES, ADD AT THE BOTTOM ...

            kryo = new Kryo();
            kryo.setRegistrationRequired(true);

            kryo.register(Class.class);
            kryo.register(HashMap.class);
            kryo.register(ArrayList.class);
            kryo.register(BigDecimal.class);
            kryo.register(Date.class);

            // This one is required for the special cases where we are using Arrays.asList() functionality ...
            kryo.register(Arrays.asList("").getClass(), new ArrayAsListSerializer());

            kryo.register(Ticker.class, new TickerSerializer());
            kryo.register(Commands.class, new CommandsSerializer());
            kryo.register(LongId.class);
            kryo.register(User.class);
            kryo.register(Message.class);
            kryo.register(MessageContext.class);
            kryo.register(Quote.class, new CompatibleFieldSerializer(kryo, Quote.class));
            kryo.register(DirectionSymbol.class);
            kryo.register(HaltIndicatorCode.class);
            kryo.register(HaltStatusCode.class);
            kryo.register(QuoteSource.class);
            kryo.register(QuoteType.class);
            kryo.register(WriteProtectedTicker.class, new TickerSerializer());

            // Cache the kryo instance ...
            converters.set(kryo);
        }

        return kryo;
    }

    /**
     * This serializer is used to represent a compact representation of a command when sent over the wire.
     * <p>
     */
    private static final class CommandsSerializer implements Serializer<Commands> {
        public Commands read(Kryo kryo, Input input, Class<Commands> tickerClass) {
            return Commands.GET_REALTIME_QUOTE.fromCode(input.readByte());
        }

        public void write(Kryo kryo, Output output, Commands command) {
            output.writeByte(command.getCode());
        }
    }

    /**
     * This serializer is used to represent a compact representation of a ticker when sent over the wire.
     * <p>
     */
    private static final class TickerSerializer implements Serializer<Ticker> {

        public Ticker read(Kryo kryo, Input input, Class<Ticker> tickerClass) {
            String cusip = kryo.readObject(input, String.class);
            String symbol = kryo.readObject(input, String.class);
            String exchangeName = kryo.readObject(input, String.class);

            Ticker ticker = new Ticker();
            ticker.setCusip(cusip);
            ticker.setSymbol(symbol);
            ticker.setExchange(Exchange.NYSE.fromMappedValue(exchangeName));

            return ticker;
        }

        public void write(Kryo kryo, Output output, Ticker ticker) {
            String symbol = ticker.getSymbol();
            String cusip = ticker.getCusip();
            String exchange = ticker.getExchange().toMappedValue();

            kryo.writeObject(output, cusip);
            kryo.writeObject(output, symbol);
            kryo.writeObject(output, exchange);
        }
    }

    /**
     * This serializer is used for transforming lists built using the Arrays.asList() function.
     * <p>
     */
    private static final class ArrayAsListSerializer extends ArraySerializer {
        private Field arrayField;

        public ArrayAsListSerializer() {
            try {
                arrayField = Class.forName("java.util.Arrays$ArrayList").getDeclaredField("a");
                arrayField.setAccessible(true);
            } catch (final Exception e) {
                throw new RuntimeException(e);
            }
        }

        public Object read(Kryo kryo, Input input, Class listClass) {
            Object[] array = (Object[]) super.read(kryo, input, Object[].class);
            return Arrays.asList(array);
        }

        public void write(Kryo kryo, Output output, Object list) {
            try {
                final Object[] array = (Object[]) arrayField.get(list);
                super.write(kryo, output, array);
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        }
    }
}
Original issue reported on code.google.com by andhappi...@gmail.com on 17 Apr 2012 at 10:39
Avi-Levi / kryo

Deserialization failing randomly - version 2.02 #57
