Cache J2EE

• Licence : Apache modifiée
• Points remarquables :
  • Taglib utilisable dans les JSP (cache par fragments)
  • Permet de bloquer les accès jusqu'à la fin d'une maj
  • Servlet Filter pour le cache

String myKey = "myKey";
String myValue;
int myRefreshPeriod = 1000;
try {
    // Get from the cache
    myValue = (String) admin.getFromCache(myKey, myRefreshPeriod);
} catch (NeedsRefreshException nre) {
    try {
        // Get the value (probably from the database)
        myValue = "This is the content retrieved.";
        // Store in the cache
        admin.putInCache(myKey, myValue);
    } catch (Exception ex) {
        // We have the current content if we want fail-over.
        myValue = (String) nre.getCacheContent();
        // It is essential that cancelUpdate is called if the
        // cached content is not rebuilt
        admin.cancelUpdate(myKey);
    }
}

String myKey = "myKey";
String myValue;
int myRefreshPeriod = 1000;
try {
    // Get from the cache
    myValue = (String) admin.getFromCache(myKey, myRefreshPeriod);
} catch (NeedsRefreshException nre) {
    try {
        // Get the value (probably from the database)
        myValue = "This is the content retrieved.";
        // Store in the cache
        admin.putInCache(myKey, myValue);
        updated = true;
    } finally {
        if (!updated) {
            // It is essential that cancelUpdate is called if the
            // cached content could not be rebuilt
            admin.cancelUpdate(myKey);
        }
    }
}

• http://www.opensymphony.com/oscache/wiki/Documentation.html
• http://www.opensymphony.com/oscache/wiki/API Usage.html
• http://www.opensymphony.com/oscache/wiki/Configuration.html

• Licence : Apache 2.0
• Dépendances : common-collection et common-logging
• Points remarquables :
  • Plusieurs politiques d'expiration de cache : LRU, LFU, FIFO
  • Multiples CacheManager par JVM
  • Fonctionne avec Hibernate
  • 86 % de “code coverage” pour les tests unitaires
  • Fonction de “vérouillage” du cache par un thread et de mise en attente des autres

WEB-INF/ehCache.xml

<ehcache>
 
    <diskStore path="java.io.tmpdir"/>
 
    <defaultCache
        maxElementsInMemory="10000"
        eternal="false"
        timeToIdleSeconds="120"
        timeToLiveSeconds="120"
        overflowToDisk="true"
        diskPersistent="false"
        diskExpiryThreadIntervalSeconds="120"
        />
 
    <cache name="sampleCache1"
        maxElementsInMemory="10000"
        eternal="false"
        overflowToDisk="false"
        timeToIdleSeconds="300"
        timeToLiveSeconds="600"
        />
 
</ehcache>

public class TestServlet extends HttpServlet {
 
private static Logger logger = Logger.getLogger(TestServlet.class.getName());
private CacheManager manager = null;
private Cache cache = null;
 
public void init() throws ServletException {
       // Configuration de log4J.
       PropertyConfigurator.configure( getServletContext().getRealPath ("WEB-INF/log4j.properties"));
       // Creating the cache manager from configuration file
       try {
           manager = CacheManager.create(getServletContext().getRealPath ("WEB-INF/ehCache.xml"));
           cache = manager.getCache("sampleCache1");
       } catch (Exception e) {
           logger.error("Unable to load EHCACHE configuration file");
       }
}
 
public void destroy() {
}
 
protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       // Creation du writer de sortie.
       PrintWriter out = response.getWriter();
       // Creation d'un objet
       Object myObject = new Object();
       // Mise en cache de cet element
       Element element = new Element("testID", myObject);
       cache.put(element);
       out.println ("Objet mis en cache<br/>");   
       // Lecture du cache pour extraire l'objet
       try {
           element = cache.get("testID");
       } catch (Exception e) {}
       Object mySecondObject = element.getValue();
}
}

• http://ehcache.sourceforge.net/
• http://www.tellaw.org/index.php?2005/04/22/16-gerer-un-cache-avec-ehcache

Licence : LGPL Dépendances : JavaGroups, commons-collections et commons-logging Points remarquables :

• Spécialisation dans la gestion de cache “clusterisables”
• Fonctionne avec Hibernate

public class PersonCache extends GenericEntity {
 
        ObjectCache cache;
 
        public PersonEntity(CacheFactory cacheFactory) {
                cache = cacheFactory.createCache("Person");
                // * Other initialization here
        }
 
        public Person get(long key) {
                Long cacheKey = new Long(key);
                Person person = (Person)cache.get(cachekey);
                if (person == null) {
                        // * Get the object from the database                   
                        if (person != null) {
                                // Put it in the cache
                                cache.put(cacheKey, person);
                        }
                }
                return person;
        }
 
        public void insert(Person person) {
                // * Do database insert
                // Add new object to cache
                Long cacheKey = new Long(person.getKey());
                cache.put(cacheKey, person);
        }
 
        public void update(Person person) {
                // * Do database update
                // Remove object from cache
                // (This causes all caches in the group to be notified)
                Long cacheKey = new Long(person.getKey());
                cache.clear(cacheKey);
                // Re-add the object to the cache
                cache.put(cacheKey, person);
        }
 
        public void delete(long key) {
                // * Do database delete
                // Remove object from cache
                // (This causes all caches in the group to be notified)
                Long cacheKey = new Long(key);
                cache.clear(cacheKey);          
        }
 
}

• http://swarmcache.sourceforge.net/tutorial.html

• Licence : LGPL
• Points remarquables :
  • Permet de cacher une arborescence d'objets “TreeCache”
  • Fonctionne avec Hibernate

ArrayList list = new ArrayList();
list.add("first");
cache.putObject("/list/test", list); // Put the list under the aop cache
list.add("second"); // Won't work since AOP intercepts the dynamic proxy not the original POJO.
ArrayList myList = (List)cache.getObject("/list/test"); // we are getting a dynamic proxy instead
myList.add("second"); // it works now
myList.add("third");
myList.remove("third");

• http://labs.jboss.com/portal/jbosscache/
• http://www.onjava.com/pub/a/onjava/2005/11/09/jboss-pojo-cache.html
• http://wiki.jboss.org/wiki/Wiki.jsp?page=WhatShouldWeExpectOfThePojoCachePerformance