`StreamOperations.map(…)` does not retain target type hint

[huan1993]

description

Today, when I read a message of type ObjectRecord from Redis Stream, the following exception occurred. I don't know how to solve it.

error info

2021-11-10 14:05:11.457  INFO 8754 --- [           main] c.h.study.redis.RedisStreamApplication   : Started RedisStreamApplication in 2.598 seconds (JVM running for 3.399)
2021-11-10 14:05:11.566  INFO 8754 --- [           main] c.h.s.r.stream.producer.StreamProducer   : generator book info :[Book(title=Time To Murder And Create, author=Vito Denesik)]
2021-11-10 14:05:11.662  INFO 8754 --- [           main] c.h.s.r.stream.producer.StreamProducer   : return record-id:[1636524311682-0]
Exception in thread "xread-nonblock-02" java.lang.IllegalArgumentException: Value must not be null!
	at org.springframework.util.Assert.notNull(Assert.java:201)
	at org.springframework.data.redis.connection.stream.Record.of(Record.java:81)
	at org.springframework.data.redis.connection.stream.MapRecord.toObjectRecord(MapRecord.java:147)
	at org.springframework.data.redis.core.StreamObjectMapper.toObjectRecord(StreamObjectMapper.java:138)
	at org.springframework.data.redis.core.StreamObjectMapper.toObjectRecords(StreamObjectMapper.java:164)
	at org.springframework.data.redis.core.StreamOperations.map(StreamOperations.java:594)
	at org.springframework.data.redis.core.StreamOperations.read(StreamOperations.java:413)
	at com.huan.study.redis.stream.consumer.xread.XreadNonBlockConsumer02.lambda$afterPropertiesSet$1(XreadNonBlockConsumer02.java:62)
	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
	at java.base/java.lang.Thread.run(Thread.java:834)

core code

@Bean
public RedisTemplate<String, Object> redisTemplate(RedisConnectionFactory connectionFactory) {
    RedisTemplate<String, Object> redisTemplate = new RedisTemplate<>();
    redisTemplate.setConnectionFactory(connectionFactory);
    redisTemplate.setKeySerializer(new StringRedisSerializer());
    redisTemplate.setValueSerializer(new StringRedisSerializer());
    redisTemplate.setHashKeySerializer(new StringRedisSerializer());
    redisTemplate.setHashValueSerializer(new Jackson2JsonRedisSerializer<>(Object.class));
    return redisTemplate;
}

The code is very easy, that is, the producer generates an ObjectRecord type message, and then the consumer consumes the message.

The following is a complete example to reproduce this problem

https://github.com/huan1993/spring-data-redis-stream

[mp911de]

There are two issues coming together. First, Jackson2JsonRedisSerializer serializes strings into a Base64 representation. It doesn't deserialize Base64 back into a String, therefore the type hint is lost.

Second, StreamOperations.map(…) does not propagate the type hint into the ObjectHashMapper which is unfortunate. Those both aspects together cause the issue. Please use the regular StringRedisSerializer for the time being as hash value serializer.

[huan1993]

I tried it, use StringRedisSerializer program can run normally.
thanks.

[mp911de]

Let's keep this one open as we still need to fix the type hint propagation.