OpenCms startup

This page tries to explain the OpenCms 7 bootup process. You may find it useful if you are interested in the OpenCms internals.

The boot up phase happens in several stages called runlevels, a similar concept to the UNIX runlevels.

• When the OpenCms webapp is not initialized , it is said to be at runlevel 0. At this stage the OpenCmsCore singleton is not instantiated, nothing is really running yet. The system is also at runlevel 0 when shutdown is requested.
• At runlevel 1, the OpenCmsCore singleton is instantiated, and some of the core services are available from it. The configuration hasn't yet been read.
• At runlevel 2, configuration begins. The XML config files are read, and all remaining core services are instantiated and initialised. During this process, some of the services created at runlevel 1 are swapped with different implementations, as configured in the config files; one example is the CmsEventManager service.
• At runlevel 3, configuration finished and all the internal services are configured and running. HTTP serving is disabled. The CMS Shell operates at this runlevel.
• At runlevel 4, HTTP request serving is enabled, the system is operating normally.

Runlevels are defined in class org.opencms.main.OpenCms.