Best practice for updating HashMap for Object Cache

Question

I'm developing a RESTful web service using Jersey and I'm going to be using a simple object cache that is updating it's data by retrieving records from a database based on a timer. I plan on using a HashMap to store my retrieved data in this cache but my question is what is the best practice for updating this HashMap.

Right now my choices are making the HashMap volatile and anytime an update comes in, create a new HashMap and then assign it when it completes. I could also wrap the HashMap in a synchronized block or use a ReentrantReadWriteLock while updating the HashMap variable directly. I have also thought about using ConcurrentHashMap which seems to have some performance benefits. Are there any significant performance differences and/or drawbacks in using one of these approaches over the other?

Also, when a user updates or inserts a record through my web service API, is it best practice to update the local cache directly once I save the record in the DB or force the cache to do another big data retrieval?

Answer 1

Instead of a HashMap, consider using Guava's cache, which is much more configurable and documents your intention to cache data. Read this example.

Answer 2

Use ConcurrentLinkedHasHMap , it uses LIRS algorithm.

ConcurrentLinkedHashMap implementation is a tweaked version of the ConcurrentHashMap implementation originally coded by Doug Lea and found on OpenJDK 1.6.0_0. We present a concurrent hash map and linked list implementation of the ConcurrentMap interface, with predictable iteration order. This implementation differs from ConcurrentHashMap in that it maintains a doubly-linked list running through all of its entries. This linked list defines the iteration ordering, which is normally the order in which keys were inserted into the map (insertion-order). Note that insertion order is not affected if a key is re-inserted into the map.