The hibernate 2.1.3 document showes that treecache does not support read-write, nonstrict-read-write and query cache. Is this true?
The jbosscache 1.0 states that it supports 5 isolation levels:
SERIALIZABLE, REPEATABLE_READ (default) READ_COMMITTED,READ_UNCOMMITTED and NONE

How do they match the treecache's isolation levels to hibernate cache levels?

By the way, is that ture that query cache does not work with treecache?

We could use EHCache. The problem is that we have to manually edit ehcache.xml to include every new class or collection as it is a class level config. The good thing to use treecache is that we deploy treecache as a mbean so we can adjust its attibutes at runtime.

If we set "transactional" level caching, is there really a performance hit?

Thanks.

This is a really complex topic and you should try to understand the differences between the different concurrency strategies before you use a cache. If the current reference documentation is not enough, try "Hibernate in Action".

Yes, JBossCache/Treecache only supports transactional (and read only, of course). You would only use it in a cluster and EHCache only as a local single VM cache. You should not change the TreeCache isolation level, leave it at the default "repeatable read", which is what "transactional" in Hibernate guarantees.

There is a huge performance hit if you use "transactional", of course. It might even be not worth it to run the second-level cache! But this is not surprising nor special: You should only enable the second-level cache for read-mostly classes in any case. See the book for a more detailed discussion.

JBossCache supports the Hibernate query cache, as does EHCache.

I don't understand your question or problem about "class level config".