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5 JPie: An Environment for Live Software Construction in Java

Tuesday, 28 October – 15:00-15:45

Wednesday, 29 October – 15:00-15:45

Kenneth Goldman, Washington University in St. Louis, kjg@cse.wustl.edu

JPie is a tightly integrated development environment supporting live object-oriented software construction in Java. JPie embodies the notion of a dynamic class whose signature and implementation can be modified at run time, with changes taking effect immediately upon existing instances of the class. The result is complete elimination of the edit-compile-test cycle. Dynamic classes are precompiled and then execute in a semi-interpreted manner using an internal representation of the dynamic portions of the class definition. Dynamic classes fully interoperate with compiled classes. Consequently, JPie users have access to the entire Java API, may create dynamic classes that extend compiled classes, and can override their methods on the fly. Instances of compiled classes may hold type-safe references to instances of dynamic classes, and may call methods on them polymorphically. All of these capabilities are achieved without modification of the language or virtual machine. JPie users create and modify class definitions through direct manipulation of visual representations of program abstractions. The visual representations expose the Java execution model, while removing the possibility of syntax errors and enabling immediate type-checking feedback. In this demonstration, we will illustrate the central features of JPie in the course of constructing an example application. These will include dynamic declaration of instance variables and methods, dynamic modification of method bodies and threads, dynamic user interface construction and event handling, and on-the-fly exception handling in JPie's integrated thread-oriented debugger.