JCL is a configurable, dynamic and extensible custom classloader that loads java classes directly from Jar files and other sources. The motivation was to create isolated classloaders, which can be easily integrated with IoC frameworks like Spring and with web applications.

To load calsses in runtime java uses ClassLoader mechanism which is based on next core principles: delegation - by default uses parent-first delegation, - child ClassLoader will be used if parent is not able to find or load class.