Apache Jackrabbit

https://jackrabbit.apache.org/

https://jackrabbit.apache.org/oak/

''The Apache Jackrabbit™ content repository is a fully conforming implementation of the Content Repository for Java Technology API (JCR, specified in JSR 170 and JSR 283). A content repository is a hierarchical content store with support for structured and unstructured content, full text search, versioning, transactions, observation, and more.''

''Jackrabbit Oak is a complementary implementation of the JCR specification. It is an effort to implement a scalable and performant hierarchical content repository for use as the foundation of modern world-class web sites and other demanding content applications. ''