Redis Template won't serialize key and value - kotlin

Question

I want to use RedisTemplate on spring boot. This is my configuration file:
#Configuration
#EnableRedisRepositories
class RedisConfig {
#Value("\${spring.redis.host}")
lateinit var redisHost: String
#Value("\${spring.redis.port}")
lateinit var redisPort: String
#Bean
fun redisConnectionFactory(): JedisConnectionFactory? {
val redisStandaloneConfiguration = RedisStandaloneConfiguration()
redisStandaloneConfiguration.hostName = redisHost
redisStandaloneConfiguration.port = redisPort.toInt()
return JedisConnectionFactory(redisStandaloneConfiguration)
}
#Bean
fun redisTemplate(): RedisTemplate<Int, String> {
val redisTemplate = RedisTemplate<Int, String>()
val stringSerializer: RedisSerializer<String> = StringRedisSerializer()
redisTemplate.setConnectionFactory(redisConnectionFactory()!!)
redisTemplate.keySerializer = stringSerializer
redisTemplate.valueSerializer = stringSerializer
redisTemplate.afterPropertiesSet()
return redisTemplate
}
}
In my class i've got something like this:
#Service
class UserService {
#Autowired
var redisTemplate = RedisTemplate<Int, String>()
val user = User("1", "Mike", "Tobey", "Male", "MT#gmail.com")
val user1 = User("1", "Mike", "Tobey", "Male", "MT#gmail.com")
fun foo(user: User, user1: User) {
if (user.lastName == user1.lastName && user.firstName == user1.firstName) {
redisTemplate.opsForValue().set(user.hashCode(), user.id)
} else if (user.gender == user1.gender && user.firstName == user1.firstName) {
redisTemplate.opsForValue().set(user1.hashCode(), user1.id)
}
}
The User.class is marked as #Serializable and #RedisHash. In the redisTemplate.opsForValue().set() method, it won't recognize the key and the value at all. This is what the program returns me:
Cannot invoke "org.springframework.data.redis.serializer.RedisSerializer.serialize(Object)" because the return value of "org.springframework.data.redis.core.AbstractOperations.valueSerializer()" is null.
Can anybody help?
I tried to set key and values in value store for redisTemplate but it seems like code won't serialize those values.