Ehcache is a pure Java, in-process cache with the following features:
Acts as a pluggable cache for Hibernate 2.1.
Small foot print. Both in terms of size and memory requirements.
Fully documented. See the online Documentation, FAQ and the online JavaDoc.
Comprehensively Test Coverage. See the clover test report.
Scalable to hundreds of caches and large multi-cpu servers.
Available under the Apache 1.1 license. Ehcaches copyright and licensing has been reviewed and approved by the Apache Software Foundation, making ehcache suitable for use in Apache projects.
Production tested. All versions of ehcache are production tested for several weeks on a large and very busy eCommerce site before release.