Thread safe swap of entire map in Java-CodePudding

I'm implementing thread-safe map in the spring web service.

The map is such like this.

The map is read simultaneously in thousands of client threads.
The map's content has to be entirely updated sometimes(about once per hour).

I've chosen ConcurrentHashMap for thread-safe map, but there was no functionality to simply swap its content with newer one, like std::map::swap() in c .
(I thought that atomic update of the entire content is required for multi-thread environment, maybe I'm wrong)

Is there an alternative map with swap?

Any suggestion or reply will be appreciated. Thanks.

CodePudding user response：

If it isn't necessary to mutate the map, just atomically replacing it, you could wrap the map in an AtomicReference and atomically replace the reference in a single go. The different threads wouldn't keep a reference to the map instance itself, but the surrounding AtomicReference instance.

class Example {
    private final AtomicReference<Map<String, String>> mapRef = new AtomicReference<>(someInitialState);

    private void consumerThread() {
        // Get the current version of the map and look up a value from it.
        String value = mapRef.get().get("Hello");
        // Do something with value.
    }

    private void producerThread() {
        // Time to replace the whole map for all threads
        Map<String, String> newMap = calculateNewMap();
        mapRef.set(newMap);
    }
}