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Catching up with the Java Content Repository

by Rob Thornton on Oct 12, 2006 |

The Java Content Repository (JCR) API provides a standard way to access content repositories. Content repositories is a superset of a traditional data repository that adds features such as author based versioning, full text searching, and allows storing of structured and unstructured data. The introduction to this piece describes content respositories in more detail. Version 1.0 (JSR-170) of the JCR spec was released in June of 2005. Since then there have been several implementations, including Apache Jackrabbit, CRX, Magnolia, and the eXoplatform. An early draft of version 2.0 (JSR-283) of the spec was recently released. Points of interest about the new version include:

  • Extensions for managing a content repository, including access control, workspace and node administration, and content retention)
  • Improved interoperability through new standardized node types
  • New extensions for content modeling

OnJava has released a new article by Sunil Patil detailing the installation, configuration, and usage of a Version 1.0 implementation. It is written for developers, as opposed to many of the JCR articles out there which are intended to sell the idea of a content repository, rather than how to use it. There is a similar tutorial on IBM's developerWorks site that was recently updated and covers many of the same topics. Sunil's tutorial offers an introduction to:

what a content repository is and what is needed for standardizing the content repository API. After that I'll introduce you to JSR-170 by discussing the repository model defined by JSR-170. Next I will talk about what Apache Jackrabbit is, how to build it, and configure it for use. Once Apache Jackrabbit is set up, I will develop a sample application for demonstrating the basic features of JSR-170 API.

As JCR's become more common, tools to abstract some of the details of working with them are improving. A recent article on TheServerSide discusses a beancoder as a new way to organize and find your data within a JCR. The beancoder makes it easy to persist and retrieve JavaBeans from the repository, adding a level of object mapping that was not available before. Similarly, the Graffito project, currently incubating at Apache, provides a framework upon which to build content based applications. It provides, among many other features, a uniform model to interact with which can sit on top of relational database schemas, WEBDAV servers, or JCR repositories, allowing a uniform way to interact with these content stores. InfoQ runs on a combination of Jackrabbit and Graffito, and has contributed code to the Graffito project. The JCR expert group expects us to be programming to repositories in the future, instead of databases. If that is to happen, tools like these are a necessary step.

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great to finally see some documentation by Floyd Marinescu

Building InfoQ was quite a challenge as there was basically no documenation anywhere on the internet. It's good to see more documentation on this important infrastructural component. Using JCR has been an instrumental architectural choice for us which has netted many benefits.

Floyd

Relation to RDF/XML ? by Arnaud Bailly

Skimming through the (very clear) article, I am wondering whether and how content repositories are similar to RDF databases or more generally graph DB, which is definitely not a novel idea. Is it really useful to develop a new API for such things ?

Re: great to finally see some documentation by Lars Borup Jensen

Hi Floyd,

I didn't know InfoQ was build upon a JCR compatible repository. Do you mind sharing which implementation you are using and perhaps elaborate on the many benefits?

regards, Lars Borup

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