How to sink List to Redis in Flink

I am trying to RPUSH a string with blank spliter into a Redis List, but when I using the RPUSH in RedisSinkBuilder, the string cannot be splited.

Code:

RedisSinkBuilder<Tuple2<String, String>> builder = new RedisSinkBuilder<>();
RedisSink<Tuple2<String, String>> redisSink = builder
                        .redisMapper(new Tuple2RedisMapper())  
                        .syncType(RedisSyncType.ASYNC) 
                        .deployType(RedisType.STANDALONE)
                        .hostname(redisTestHost)
                        .port(redisTestPort)
                        .dataType(RedisDataType.LIST)
                        .redisCommand(RedisCommand.RPUSH)
                        .additionalTTL(60)
                        .build();
testDataStream.addSink(redisSink).name("test");

Example:

key: "test"
value: "1 2 3 4 5"

Expected Data in Redis:

1)"1"
2)"2"
3)"3"
4)“4"
5)"5"

However, I got only 1 element in the test list:

1)"1 2 3 4 5"

Any ideas on how I can RPUSH multiple elements in a string into a list in Redis?

Many Thanks!