GlassFish
GlassFish is an open-source application server for the Java EE (Enterprise Edition) and Jakarta EE platforms, developed by the Eclipse Foundation. It provides a robust runtime environment for deploying, managing, and executing enterprise Java applications, including web services, servlets, and EJBs. Originally created by Sun Microsystems and later Oracle, it serves as the reference implementation for Java EE/Jakarta EE specifications.
Developers should learn GlassFish when building enterprise Java applications that require full Java EE/Jakarta EE compliance, such as large-scale web services, e-commerce systems, or corporate software. It is particularly useful for testing and development due to its role as a reference implementation, ensuring adherence to standards. Use cases include deploying Java web applications, integrating with databases via JPA, and implementing security features like JAAS.