using session cache and/or second level cache

bonoddr · **Joined:** Mon Oct 03, 2005 5:13 pm **Posts:** 30

Hello everyone. I´m facing a problem.

I´ve several terminals acessing a database, inserting, updating and loading in queries. The problem is that, if I keeps a session opened and everyone uses this session, I´ve a problem of syncronizing all the data. Then I´m studying a way of use the second level cache.

Each terminal opens a new session and, when it terminates all the work, it closes his session. Doing this:

Code:

Session session = Hibernate.getNewSession();
//do some work
session.close();

Using in this way, I lost the cache mechanism. So, the solution is using the second level cache.

I want to know if these ways are correct, if there are other better ways.... Sugestions are welcome.

I´m thinking in the C3P0 to do a pool mechanism. I´m using aa ehcache with these configurations:

Code:

<defaultCache
        maxElementsInMemory="2147483647"
        eternal="false"
        overflowToDisk="true"
        timeToIdleSeconds="120"
        timeToLiveSeconds="120"
        diskPersistent="false"
        diskExpiryThreadIntervalSeconds="120"
        />

From the code, I call in this way:

Code:

static CacheManager manager = null;
//inside static {}
if (manager == null) {
         aStr = SystemConfiguration.getInstance().getProperty("hibernateCacheFile" , "../Hibernate/config/ImeEhcache.xml");
         //aStr = "../Hibernate/config/ImeEhcache.xml";
         try {
            manager = CacheManager.create(aStr);
         } catch (CacheException e) {
            e.printStackTrace();
         }
      }

caleb_phillips · **Joined:** Thu Sep 02, 2004 2:31 pm **Posts:** 12

You don't have to use the EhCache API directly, just configure Hibernate correctly and it will manage the interaction with EhCache for you.

http://www.hibernate.org/hib_docs/v3/re ... ance-cache

Also notice the section on the query cache. Enable this to cache the results of your queries (in addition to just the entities themselves).

LaLiLuna · **Posted:** Thu Jan 19, 2006 7:56 pm

May be a hint to you
a cache like EHcache is shared across a JVM.

I do not consider sharing a session by multiple threads as "stable". As somewhere in the reference " a session is a short living ..."

Configure a cache withe cache settings.
In your mapping add the cache tag.
eg

Code:

  <class name="Developer" table="tdeveloper">
  <cache usage="read-write" />

your cache is extremely large. When each object has only 1 Byte, your cache will have a total of 2 GB RAM.

When I serialize a simple class, I get a size of about 250 Bytes.

Regards Sebastian