DATAREDIS-392 - Add Gerneric Jackson2 RedisSerializer.

[christophstrobl]

We introduced GenericJackson2JsonRedisSerializer holding a preconfigured ObjectMapper which writes class type informations into the JSON structure. This enables polymorphic deserialization and allows RedisCacheManager to operate upon a RedisTemplate storing data in JSON format, which had until this only been possible using the JdkSerializer.

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Alternative Implementation for #136

[odrotbohm]

Do we need an additional overload that takes an ObjectMapper and the type key?

[christophstrobl]

which benefit would we offer by adding that one? If we offer that we'd need to take care of potential configuration already done on the mapper before handing it to the serializer. I'd rather leave it completely to the user to configure the mapper when using this option.

[kgdngitfk]

I have read the source code and the data store into redis,I think the GenericJackson2JsonRedisSerializer
seri serialize(Object val) convert val to JSON with the key "@Class": "com.xx.xx.Data" which value use for
deserialize() to the corresponding java Type,isn't it?

[christophstrobl]

@kgdngitfk yes. It's using an ObjectMapper having defaultTyping enabled.