I to all.


I have a simple problem with some [ehcache + hibernate] application.


Basically, I have two classes


@Entity
@Inheritance(strategy=InheritanceType.JOINED)
@Cache(usage = CacheConcurrencyStrategy.READ_ONLY)
public abstract class Item extends BaseObject implements Serializable{
(...)


and

@Entity
public class SimpleItem extends Item implements Serializable{
(...)


as you can see, one is abstract and the other is concrete. My application only
deals with concrete one, of course.


I have a simple DAO for managing SimpleItem instances.


My configuration is ok : I can save, read, update (aso) SimpleItems.
I have an Open Session in view filter in place for managing transactions.
Everything work smoothly as I expected.


I now want to enable some caching for those entities.

I plugged ehcache, added configuration in my entities (as you saw above), configured ehcache
and hopped things will work...


Here is the usual suspects :


hibernate.cfg.file
------------------
<hibernate-configuration>
<session-factory>
<mapping class="system.model.BaseObject" />
<mapping class="system.model.entities.Item" />
<mapping class="system.model.entities.SimpleItem" />
</session-factory>
</hibernate-configuration>


spring hibernate configuration file
------------------
<bean id="sessionFactory" class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
<property name="dataSource"><ref bean="dataSource"/></property>
<property name="configLocation"><value>/WEB-INF/hibernate.cfg.xml</value></property>
<property name="configurationClass"><value>org.hibernate.cfg.AnnotationConfiguration</value></property>
<property name="hibernateProperties">
<props>
<prop key="hibernate.dialect">org.hibernate.dialect.HSQLDialect</prop>
<prop key="hibernate.hbm2ddl.auto">update</prop>
<prop key="hibernate.show_sql">true</prop>
<prop key="hibernate.cache.provider_class">org.hibernate.cache.EhCacheProvider</prop>
</props>
</property>
</bean>

ehcache.xml (note : dummy copy/paste from the web...)
---------------
<?xml version="1.0" encoding="UTF-8"?>
<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>



When I startup my application, I have the following traces :


2006-06-12 12:16:25,234 INFO org.hibernate.cfg.SettingsFactory - Second-level cache: enabled
2006-06-12 12:16:25,234 INFO org.hibernate.cfg.SettingsFactory - Query cache: disabled
2006-06-12 12:16:25,234 INFO org.hibernate.cfg.SettingsFactory - Cache provider: org.hibernate.cache.EhCacheProvider
(...)
2006-06-12 12:16:26,843 WARN org.hibernate.cache.CacheFactory - read-only cache configured for mutable class:
system.model.entities.Item
2006-06-12 12:16:26,843 WARN org.hibernate.cache.EhCacheProvider - Could not find configuration [
system.model.entities.Item]; using defaults.


Guess what my problem is ?

The cache doesn't work !

Hibernate always trigger some SQL when I try to fetch SimpleItem instances.

I highly suspect a configuration problem, but didn't succeeded finding a satysfiying answer
in all the documentation I read.
The second warning must probably lead my to a solution, but I must confess that I'm running in circle...

I'm highly disapointed and beg all for some help, enlightenment and salvation ! ;)

thanks in advance,

Sne.

goto user forum. this is tools related.


...and remember that "enable caching" != no sql

Ok, sorry for the wrong place post ! ;)

Ok for ["enable caching" != no sql] => but is this possible with a simple select all ?

but i checked objects references too (hashcode) and they were different each time I load the List.

of course they are different - otherwise the objects would be shared between sessions and you would have concurrency issues etc.

i recommend reading up on how second level cache actually works.

Ok ! ;)

I'm new to second level caching and thought I would get it easily... obviously not !

Any good resource you could advise me to read beyond hibernate documentation ?


EDIT :
Ok.
I tried

getSessionFactory().getStatistics()
.getSecondLevelCacheStatistics("system.model.entities.Item")
.getEntries());

before and after a first call proved me that obviously, the cache was filled with objects returned by query.

So objects are put to the cache.

Something I didn't get is that, after having set the logging level to "debug",
it's OBVIOUS that hibernate make some SQL call.

FIRST CALL :
2006-06-12 15:02:02,453 DEBUG org.hibernate.jdbc.ConnectionManager - opening JDBC connection
2006-06-12 15:02:02,453 DEBUG org.hibernate.SQL - select this_.id as id1_0_, this_1_.name as name1_0_, this_1_.descrip
tion as descript3_1_0_ from SimpleItem this_ inner join Item this_1_ on this_.id=this_1_.id
Hibernate: select this_.id as id1_0_, this_1_.name as name1_0_, this_1_.description as descript3_1_0_ from SimpleItem th
is_ inner join Item this_1_ on this_.id=this_1_.id
2006-06-12 15:02:02,453 DEBUG org.hibernate.jdbc.AbstractBatcher - preparing statement
2006-06-12 15:02:02,468 DEBUG org.hibernate.jdbc.AbstractBatcher - about to open ResultSet (open ResultSets: 0, global
ly: 0)
2006-06-12 15:02:02,468 DEBUG org.hibernate.loader.Loader - processing result set
2006-06-12 15:02:02,468 DEBUG org.hibernate.loader.Loader - result set row: 0
2006-06-12 15:02:02,468 DEBUG org.hibernate.type.LongType - returning '1' as column: id1_0_

SECOND :
2006-06-12 15:02:45,890 DEBUG org.hibernate.jdbc.AbstractBatcher - about to open PreparedStatement (open PreparedState
ments: 0, globally: 0)
2006-06-12 15:02:45,890 DEBUG org.hibernate.jdbc.ConnectionManager - opening JDBC connection
2006-06-12 15:02:45,890 DEBUG org.hibernate.SQL - select this_.id as id1_0_, this_1_.name as name1_0_, this_1_.descrip
tion as descript3_1_0_ from SimpleItem this_ inner join Item this_1_ on this_.id=this_1_.id
Hibernate: select this_.id as id1_0_, this_1_.name as name1_0_, this_1_.description as descript3_1_0_ from SimpleItem th
is_ inner join Item this_1_ on this_.id=this_1_.id
2006-06-12 15:02:45,890 DEBUG org.hibernate.jdbc.AbstractBatcher - preparing statement
2006-06-12 15:02:45,890 DEBUG org.hibernate.jdbc.AbstractBatcher - about to open ResultSet (open ResultSets: 0, global
ly: 0)
2006-06-12 15:02:45,890 DEBUG org.hibernate.loader.Loader - processing result set
2006-06-12 15:02:45,890 DEBUG org.hibernate.loader.Loader - result set row: 0
2006-06-12 15:02:45,890 DEBUG org.hibernate.type.LongType - returning '1' as column: id1_0_



So what is the probleme here ?
I re-read a part of a book on Hibernate 3 (in french) and it was clearly saying that there will be no sql invovled in a second call if cache is enabled (in the case of a READ-ONLY cached entity)...

Am I missing something ?

Thank you for your time,

Seb.

Hibernate In Action

Ok. Just re-read the cache section on Hibernate in Action.

Obviously, there is a clear and important distinction between collection caching and instance caching.

But it wasn't clear to me on how a call to a method like
public List loadAll(Class entityClass)
can be cached ?

I can tell ehcache to cache a collection (association or composition for exemple) for a given class, but how can I tell him to cache a loadAll result ?

Must I make use a query cache ???

i think you will have much better chance of getting an answer if you ask it in the user forum ;)