Catch Jackrabbit and the Java Content Repository API "If the Java Content Repository (JCR) API expert group's vision bears out, in five or ten years' time we will all program to repositories, not databases, according to David Nuescheler, CTO of Day Software , and JSR 170 spec lead. Repositories are an outgrowth of many years of data management research, and are best understood as fancy object stores especially suited to today's applications."
"The Jackrabbit code base contains not only the JCR API reference implementation, but also a fully functional repository as well as several contributed libraries for tasks, such as accessing a remote repository via RMI. There is even a JDBC persistence manager to allow plugging in a relational database as a persistent store, and an object-relational mapping tool that allows Hibernate applications to use the repository."
"The default Jackrabbit repository is based on the file system. However, Jackrabbit provides a JDBC persistence manager that relegates data storage to a relational database. As any JCR-compliant repository, Jackrabbit can be accessed through any protocol such as WebDAV or RMI. Examples for different repository access modes are included in the Jackrabbit source distribution."
"Still, for a public blogging "superstore" to have real value to application developers, for instance, some agreement on the node types supporting a blogging data model would be helpful. The repository community has so far avoided the politically sensitive pitfalls of trying to initiate agreement about such information models. The jury is still out whether truly universal data "superstores" can emerge in the absence of such shared data models, or if they will remain a dream befitting Utopia."