Originally developed as a Python interpreter that produced Java source code, gxp was rewritten in 2006-7 to be a completely Java based application. The idea behind gxp is fairly simple (and is one that is used, in slightly different fashion, for Microsoft's XAML and Silverlight) - a web designer can declare a number of XML namespaces that define specific libraries on an XHTML or gxp container element, intermixing gxp and XHTML code in order to perform conditional logic, invoke server components, define state variables or create template modules. This gxp code is then parsed and used to generate the relevant Java code, which in turn is compiled into a server module invoked from within a Java servlet engine such as Tomcat or Jetty and cached on the server.
