JDK 1.6 or higher.

Yes. You use 1 instance of Ehcache and 1 ehcache.xml. You configure your caches with Hibernate names for use by Hibernate. You can have other caches that you interact with directly, outside of Hibernate.

For Hibernate we have about 80 Domain Object caches, ten StandardQueryCaches, 15 Domain Object Collection caches. We have around five general caches we interact with directly using BlockingCacheManager. We have 15 general caches we interact with directly using SelfPopulatingCacheManager. You can use one of those or you can use CacheManager directly. See the tests for example code on using the caches directly. Look at CacheManagerTest, CacheTest and SelfPopulatingCacheTest.

This is a Hibernate 3 bug. See http://opensource.atlassian.com/projects/hibernate/browse/HHH-3392 for tracking. It is fixed in 3.3.0.CR2, which was released in July 2008.

See the OSGi section in the Configuration Guide for BigMemory Max. If you are not using distributed cache, leave out the <terracotta> element shown in the configuration example.

Version 1.6 is compatible. SeeUsing Ehcache with the Google App Engine.

ActiveMQ seems to have a bug in at least ActiveMQ 5.1, where it does not cleanup temporary queues, even though they have been deleted. That bug appears to be long standing but was thought to have been fixed. See http://issues.apache.org/activemq/browse/AMQ-1255.

The JMSCacheLoader uses temporary reply queues when loading. The Active MQ issue is readily reproduced in Ehcache integration testing. Accordingly, use of the JMSCacheLoader with ActiveMQ is not recommended. Open MQ tests fine.

Tomcat is such a common deployment option for applications using Ehcache that there is a page on known issues and recommended practices. See Tomcat Issues and Best Practices.