Logback

Log4j, a software designed by Ceki Gülcü, founder of log4j, is an exceptional logging system that draws on years of experience building high-performance systems as far back as 1999. The key advantage of logback's basic design is that it's versatile enough to use under various conditions.

Logback is presently split into three modules, namely logback-core, logback-classic and logback-access. The logback-core module sets a solid foundation for the other two modules. The logback-classic module can be described as an improved version of log4j. Therefore, logback-classic natively implements the SLF4J API, allowing the smooth transition between Logback and other logging systems such as java.util.logging (JUL) or log4j.

The logback-access module integrates with Servlet containers like Tomcat and Jetty, to offer HTTP-access log functionality. Also, logback-core is extendable, meaning developers can easily create their own modules on top of it. It is worth noting that logback is developed, provided and licensed under the terms of the GNU Lesser General Public License Version 2.1, making it open-source software.

In summary, logback is an excellent software system that stands out for its versatility, solid architecture, and the SLF4J API integration. The three modules make it possible to build a custom logging system tailored for your specific software project. Additionally, its open-source nature allows developers to modify the code and contribute to the community.