kryo处理unmodifiedList报错问题

序列化的对象如下

public class MixedData{
private Proto.RepeatedModel protoData;
private int normalData;
}

proto模型定义如下

message RepeatedModel {
repeated int32 data;
}

关键报错信息如下

Caused by: java.lang.UnsupportedOperationException
    at java.util.Collections$UnmodifiableCollection.add(Collections.java:1075)
    at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:109)
    at com.esotericsoftware.kryo.serializers.CollectionSerializer.read(CollectionSerializer.java:22)
    at com.esotericsoftware.kryo.Kryo.readObject(Kryo.java:679)
    at com.esotericsoftware.kryo.serializers.ObjectField.read(ObjectField.java:106)
    ... 48 more

原因很清楚, 对于repeated字段,proto编译生成的是UnmodifiedList,kryo中没有注册UnModifiedList的序列化器,使用了CollectionSerializer去做序列化,CollectionSerializer的反序列化策略关键点如下

    for (int i = 0; i < length; i++)
                    collection.add(kryo.readObject(input, elementClass, serializer));

这里的collection是由序列化使用的list类型决定的,在本文就是UnmodifiableCollection,一切至此明了.

一个可行的解决方案如下(未测试)
添加如下依赖

        <dependency>
            <groupId>de.javakaffee</groupId>
            <artifactId>kryo-serializers</artifactId>
            <version>0.42</version>
        </dependency>

在kryo配置处注册serializer

            this.register(UnmodifiableCollectionsSerializer.class);