From what appears to be a long way from where JSR 223 started, Mustang gets a common scripting framework for integrating scripting engines with the Java platform. From evaluating the scripting source, to compiling and invoking, your Java programs can be bilingual with full object transparency between the two languages. In fact, you can even implement interfaces on the fly in the scripting language if you want to, without even generating .class files. As you get started with scripting, be sure to test your scripts in the command-line support tool.
The book’s final chapter looks at the last big additions to Mustang—improvements in the pluggable annotation processing area. First introduced with Java 1.5, the metadata facility allows the marking of attributes for classes, interfaces, fields, and methods. In Chapter 10, you’ll discover the additional features available for the processing of your types and elements.