I tried submitting this as a bug but it was rejected with an explanation that I was doing something wrong, so now I'm turning to the forums in the hope that someone can help me figure out a little bit more about what I might be doing wrong.

The issue is this: I'm trying to get the contents of a second level cache.
Here's my code:


Inside SecondLevelCacheStatistics.java, the following method is being called:

I'm receiving a ClassCastException on line 50 because, in addition to the keys in the map that are of type CacheKey, there are keys in the map that are of type QueryKey.

The comment that was added to my bug when I posted it said "Don't try to cache queries in a second-level cache region." The thing is, I'm not trying to cache queries in a second-level cache region. They're clearly there, but I haven't intentionally done anything to put them there. Does anyone have any idea how this might happen?

A little more info:
I have hibernate.cache.use_query_cache set to true in my hibernate cfg file. If I set it to false, the issue goes away. I'm using EHCache and I have the usage of the cache for my object set to read-only. I have not explicitly set any queries to use this cache region. I have only set use_query_cache to true and added the cache tag to my class in the hibernate mapping file.

Any thoughts about how I am misusing the second level cache would be greatly appreciated.

Thanks,
Max

Hibernate version:
3.0.4
Mapping documents:
<hibernate-configuration>
<session-factory name="HibernateSessionFactory">
<property name="show_sql">false</property>
<property name="hibernate.cache.use_query_cache">true</property>
<property name="hibernate.cache.use_structure_entries">false</property>
<property name="hibernate.generate_statistics">true</property>
<property name="dialect">org.hibernate.dialect.MySQLInnoDBDialect</property>
<property name="connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="connection.url">jdbc:mysql://localhost:3306/max</property>
<property name="connection.username">max_user</property>
<property name="connection.password">max</property>
<property name="connection.isolation">4</property>
<property name="hibernate.c3p0.min_size">5</property>
<property name="hibernate.c3p0.max_size">20</property>
<property name="hibernate.c3p0.timeout">1800</property>
<property name="hibernate.c3p0.max_statements">50</property>
</session-factory>
</hibernate-configuration>


From my hibernate mapping file:
<class name="GoblRoleHb" table="GoblRole">
<cache usage="read-only" region="ACCESS_CONTROL" />
<id name="goblRoleId" column="GoblRoleId" type="string">
<generator class="assigned"/>
</id>
</class>

Code between sessionFactory.openSession() and session.close():
My code is not executing inside a session, but I'm trying to access a second level cache so I shouldn't need to be.

Full stack trace of any exception that occurs:
java.lang.ClassCastException: org.hibernate.cache.QueryKey
at org.hibernate.stat.SecondLevelCacheStatistics.getEntries(SecondLevelCacheStatistics.java:50)
Name and version of the database you are using:
MySql 4.1.10

I've been stepping through the Hibernate code, trying to figure exactly how the QueryKey is making its way into my second level cache, and it's not sneaky at all. From Loader.java, lines 1506 through 1527


Unless I'm misreading, if the object is associated with a cache region and the cache is enabled, we get the cache from the session factory and, once the query has been executed, store the QueryKey in the cache. Am I somehow getting the wrong type of cache on line 1506?

Like I said in the JIRA issue, don't cache queries in the same region as you cache an entity!

I mean, this is trivial to avoid; you have to have explicity type Query.setCacheRegion(...) somewhere in your code to cause this problem to happen!

Yup, trivial indeed. Another team member was setting the cache region of a query and I wasn't aware of it. Now it all makes sense. Sorry for the trouble, and thanks for the response.

no, that does not fix it. There appears to be a problem here.