openEQUELLA began life a long time ago in 2002 and as such has had fair share of code re-strucures over the years. As of version 6.6 the code mostly fits into two categories; the "new" architecture or the "legacy" architecture.
- Written in Java (some Java 8 features)
- In house web framework called Sections for server side rendering with some facility for doing AJAX DOM updates somewhat transparently
- XML based extension declarations (JPF)
- Freemarker, JQuery, Boostrap
- Hibernate (3.6)
- JAX-RS based REST APIs (not used by web site)
- Java and Scala can be used
- Separate backend/frontend
- REST APIs on backend
- ReactJS for frontend
- Material UI React library
- Typescript/Purescript for frontend code
- Typesafe SQL tables/queries instead of hibernate magic
- Put extensions in compiled code instead of XML
95% of the openEQUELLA is still written with the legacy architecture but the idea is to leave that untouched until something major needs to be done to a particular area and only that area will be refactored.
All the guides will concentrate on the new architecture.
Originally EQUELLA was built out of several hundred "plugins" which each had their own classpath and dependencies. However for a few reasons (lack of typesafety for core functionality, slowness of build system, complexity) the number of plugins was cut back to a minimum. Fore "core" functionality, rather than creating a completely new plugin and filling out the various XML extension points, you should simply add your classes to an existing (or new) package inside one of a few select plugins:
Inside Source/Plugins/Core:
com.equella.core- Anything related to the web site, frontend or backend.com.equella.serverbase- Classes that don't have an affiliation with the web, e.g. DB access, core services.com.equella.base- Classes shared between admin console and web site.com.equella.admin- Admin console.com.equella.reporting- Classes related to reporting with BIRT.
Usually com.equella.core is the place where new architecture classes will be placed.