Question about RedisTemplate and RedisSerializers

I am learning Spring Data Redis, and need some help with the RedisTemplate:

1. Looking at the javadoc of RedisTemplate, I can see the following serializer setters:

   • public void setKeySerializer(RedisSerializer<?> serializer)
   • public void setHashKeySerializer(RedisSerializer<?> hashKeySerializer)
   • public void setValueSerializer(RedisSerializer<?> serializer)
   • public void setHashValueSerializer(RedisSerializer<?> hashValueSerializer)

   I wonder when is the framework using which of the serializers? What's the difference between the ones with 'Hash" and the ones without?

2. In order to use Redis Spring Data Repositories where secondary index matching is supported, I should provide a RedisTemplate with default setting and name it redisTemplate, right?

3. What happens when I need both pub/sub with custom message body format (say json) and Spring Data repository in the same app? Should I define a default RedisTemplate (like point 2) for the repositories and create my own configuration class to build the message publisher instead of registering another RedisTemplate with Jackson2JsonRedisSerializer?

Thanks in advance for the help!