Posts tagged ‘ehcache’

ehcache and spring

As used by Hibernate, ehcache is a great little caching implementation which ought to be part of every Java coders arsenal. Although its complexities may seem overwhelming, it’s very easy to use as a simple caching solution.

In my situation, I needed to prevent db hits when validating codes (ie seeing if they already exist in the db). This is how easy it is to set up.

applicationContext.xml:

<bean id="myDao" class="myDaoImpl" init-method="setupCache">
  <property name="cacheManager" ref="cacheManager">
</bean>
<bean id="cacheManager" class="org.springframework.cache.ehcache.EhCacheManagerFactoryBean">
  <property name="configLocation" value="classpath:ehcache.xml" />
</bean>

ehcache.xml:

<ehcache>
  <diskStore path="java.io.tmpdir"/>
  <cache name="myCacheName"
    maxElementsInMemory="1000"
    eternal="true"
    overflowToDisk="false"/>
  <defaultCache
    maxElementsInMemory="300"
    maxElementsOnDisk="1000"
    eternal="false"
    timeToIdleSeconds="120"
    timeToLiveSeconds="120"
    overflowToDisk="true"/>
</ehcache>

myDaoImpl.java:

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

public class {
  private CacheManager cacheManager;
  private Cache myCache = null;

  public void setCacheManager(CacheManager cacheManager) {
    this.cacheManager = cacheManager;
  }

  private void setupCache() {
    String cacheName = "myCacheName";
    logger.debug("Fetching cache [" + cacheName + "]");
    myCache = cacheManager.getCache(cacheName);
  }
}

ehcache.xml needs to be put alongside applicationContext.xml (especially in the case of jar packaging). If you’re packaging a war, you can place it anywhere on the classpath and don’t need to specify the configLocation (it’s the default config name).

To use the cache, do something like this:

Element cachedObject = myCache.get(key);
if (cachedObject != null) {
  return cachedObject;
} else {
  fetch object from db
  // add to cache
  myCache.put(new Element(key, object))
  return object;
}

And that's it!

Now you’ll only hit the db when needed. Of course, it’s worth reading the reference material to see the many ways you can configure the cache. My example is purely for a 1000 object permanent memory cache, but TTL and overflow-to-disk (for example) is just as easy to set up.

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October 23, 2008 at 4:28 pm 4 comments