Java Cannot cast reactor.core.publisher.MonoDefer to EntityClass

Question

Here i try to upgrade my spring-data-redis RedisTemplate using reactive-redis ReactiveRedisTemplate which is returning Publisher. In this case, i want to change the method findCache to Mono . The problem is old findCache function that using spring-data-redis is accepting generic data, like this:

@Autowired
ReactiveRedisTemplate redisTemplate;

public <T> T findCache(String key, Class<T> clazz) {
    Object content = this.redisTemplate.opsForValue().get(key);

    if (content != null) {
      return clazz.cast(content);
    }

    return null;
  }

of course i will get error

Cannot cast reactor.core.publisher.MonoDefer to Person

then, since i want to get it to work reactively i update this code to return publisher, like this:

if (content != null) {
      return ((Mono) content).flatMap(o -> clazz.cast(o));
    }

but it also won't work since my findCache accepting generic. what supposed i need to do, please help.

Answer 1

It would be better to specify ReactiveRedisTemplate parameters. But if you can't, you should change your content type to Mono<Object> . Something like this:

public <T> Mono<T> findCache(String key, Class<T> clazz) {
    @SuppressWarnings("unchecked")
    Mono<Object> contentMono = redisTemplate.opsForValue().get(key);
    return contentMono.map(clazz::cast);
}

And if cache doesn't contain value for given key, it returns empty Mono, not null.