hello world example for ehcache?

Question

ehcache is a hugely configurable beast, and the examples are fairly complex, often involving many layers of interfaces.

Has anyone come across the simplest example which just caches something like a single number in memory (not distributed, no XML, just as few lines of java as possible). The number is then cached for say 60 seconds, then the next read request causes it to get a new value (e.g. by calling Random.nextInt() or similar)

Is it quicker/easier to write our own cache for something like this with a singleton and a bit of synchronization?

No Spring please.

Answer 1

EhCache comes with a failsafe configuration that has some reasonable expiration time (120 seconds). This is sufficient to get it up and running.

Imports:

import net.sf.ehcache.CacheManager; import net.sf.ehcache.Element; 

Then, creating a cache is pretty simple:

CacheManager.getInstance().addCache("test"); 

This creates a cache called test. You can have many different, separate caches all managed by the same CacheManager. Adding (key, value) pairs to this cache is as simple as:

CacheManager.getInstance().getCache("test").put(new Element(key, value)); 

Retrieving a value for a given key is as simple as:

Element elt = CacheManager.getInstance().getCache("test").get(key); return (elt == null ? null : elt.getObjectValue()); 

If you attempt to access an element after the default 120 second expiration period, the cache will return null (hence the check to see if elt is null). You can adjust the expiration period by creating your own ehcache.xml file - the documentation for that is decent on the ehcache site.