Store (v6.6)

In some cases, a cache mechanism is required. In pac4j, this is defined by the Store concept.

It has the following methods:

• get: gets a value from the store
• set: sets a value in the store
• remove: removes a value (by its key) from the store.

It has the following implementations, and you may provide your own if necessary:

• the GuavaStore: entries expire after a given timeout and the number of entries is capped. It requires the optional guava dependency
• the ConcurrentMapStore: entries expire after a given timeout as well, but the store has no maximum size. It requires no dependency at all.

val store = new ConcurrentMapStore<String, String>(5, TimeUnit.MINUTES);

When the stored values carry their own expiration date, extend the AbstractConcurrentMapStore and read the date from the value: there is then a single lifetime to define instead of two which must agree.

public class MyStore extends AbstractConcurrentMapStore<String, MyValue> {

    @Override
    protected Instant expiresAt(final MyValue value) {
        return value.getExpiresAt();
    }
}

The expiration date is computed once, when the value is stored: changing it afterwards is only taken into account on the next set. Returning null keeps the entry forever.

Entries are dropped when they expire: when they are read and when another value is stored. Neither of these two stores runs a background thread.