Thread-safely update a singleton's dependency via setter at runtime from scheduled job

Question

I have a spring based java app and my goal is to cache a bunch of objects in memory for performance and use a scheduled job to update that cache from the data source periodically.

If I am storing that map in a singleton spring bean, is there a thread safe way to update that map at runtime without making the access / service methods synchronous? Is it possible to do a temporary block of methods that are NOT synchronous on the singleton object while calling setMap(myNewMap)? Is it necessary?

class MySingletonCache {

  private Map<String, Object> myMap;

  // Called periodically from scheduled job
  public void setMap(Map<String, Object> myMap) {
    this.myMap = myMap;
  }

  // High concurrency, cannot make this synchronous
  public Object findById(String id) {
    return this.myMap.get(id);
  }

}

Answer 1

You can implement ReadWriteLock for this specific purpose.