Spring cache all elements in list separately

问题

I'm trying to add caching to a CRUD app, I started doing something like this:

@Cacheable("users")
List<User> list() {
    return userRepository.findAll()
}
@CachePut(value = "users", key = "#user.id") 
void create(User user) {
    userRepository.create(user)
}
@CachePut(value = "users", key = "#user.id") 
void update(User user) {
    userRepository.update(user)
}
@CacheEvict(value = "users", key = "#user.id") 
void delete(User user) {
    userRepository.delete(user)
}

The problem I have is that I would like that create/update/delete operations can update the elements already stored in the cache for the list() operation (note that list() is not pulling from database but an data engine), but I am not able to do it.

I would like to cache all elements returned by list() individually so all other operations can update the cache by using #user.id. Or perhaps, make all operations to update the list already stored in cache.

I read that I could evict the whole cache when it is updated, but I want to avoid something like:

@CacheEvict(value = "users", allEntries=true) 
void create(User user) {
    userRepository.create(user)
}

Is there any way to create/update/remove values within a cached collection? Or to cache all values from a collection as individual keys?

回答1:

I'll self answer my question since no one gave any and could help others.

The problem I had when dealing with this issue was a problem of misconception of Cache usage. My need posted on this question was related to how to update members of a cached list (method response). This problem cannot be solved with cache, because the cached value was the list itself and we cannot update a cached value partially.

The way I wanted to tackle this problem is related to a "map" or a distributed map, but I wanted to use the @Cacheable annotation. By using a distributed map would have achieved what I asked in my question without using @Cacheable. So, the returned list could have been updated.

So, I had (wanted) to tackle this problem using @Cacheable from other angle. Anytime the cache needed to update I refreshed it with this code.

I used below code to fix my problem:

@Cacheable("users")
List<User> list() {
    return userRepository.findAll()
}
// Refresh cache any time the cache is modified
@CacheEvict(value = "users", allEntries = true") 
void create(User user) {
    userRepository.create(user)
}
@CacheEvict(value = "users", allEntries = true") 
void update(User user) {
    userRepository.update(user)
}
@CacheEvict(value = "users", allEntries = true") 
void delete(User user) {
    userRepository.delete(user)
}

In addition, I have enabled the logging output for spring cache to ensure/learn how the cache is working:

# Log Spring Cache output
logging.level.org.springframework.cache=TRACE

来源：https://stackoverflow.com/questions/51237672/spring-cache-all-elements-in-list-separately

标签

java

Spring

spring-boot

caching

spring-cache