JEX (Java Extension) is a programming language based upon Java with built-in extensibility. JEX is a redefinition of Java using an XML syntax. This allows programmers to extend their favorite language. It also simplifies compilers, IDEs and code generators. With JEX, a project is an XML document describing the various libraries, classes, methods, etc. JEX provides a set of XSLT transformations to generate the Java class files following the JVM specification.