Standard Java Enterprise Edition (Java EE) applications used JSPs to generate presentation views for the end user. JSP is a mature technology that enables users to use embedded Java code as well as Java Server Tag Library (JSTL) elements, which will, in turn, execute Java code to generate a presentation view. All JSPs are eventually compiled as a servlet.

But mixing this Java code with presentation-specific code (HTML, CSS, and many more) is cumbersome and makes separation of concern difficult. Furthermore, presentation views done using plain JSPs are difficult to modify and maintain for UI Engineers. That is where UI template engines are useful.

Template engines provide an easy way of decoupling presentation view code from business logic so that each is layered and can be developed and maintained independently of the others. This helps vastly reduce code duplication and bugs introduced because template engines allow the reuse of previously tested, production-ready code.