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Java Forum / General / March 2005Self Modifying Code
How do you write self modifying code in Java? Japcuh (Just Another Perl C Unix Hacker) http://www.catb.org/~esr/faq/hacker-howto.htm#what_is .0. ..0 000 > How do you write self modifying code in Java? What do you mean by "modify?" A Java program can extend itself by loading new classes on the fly, if that suits your needs.  SignatureEric.Sosman@sun.com >How do you write self modifying code in Java? You can't modify a class once it has been loaded, but you can create a similar class and load that. You can do it by generating Java source and compiling that on the fly to byte codes, or by generating JVM byte codes directly. See http://mindprod.com/jgloss/eval.html http://mindprod.com/jgloss/jasm.html http://mindprod.com/jgloss/javacexe.html SignatureCanadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. japcuh@gmail.com (Japcuh) wrote in news:3a8cbb2e.0407021131.55805361 @posting.google.com: > How do you write self modifying code in Java? You may want to check out the Java code generation library cglib: http://cglib.sourceforge.net/ Best Regards Kristian Larsen > japcuh@gmail.com (Japcuh) wrote in news:3a8cbb2e.0407021131.55805361 > @posting.google.com: > > > How do you write self modifying code in Java? http://java.sun.com/developer/technicalArticles/releases/j2se15/ The metadata bit of this seems to suggest that in future releases of java, you'll be able to generate actual source code on the fly. > > japcuh@gmail.com (Japcuh) wrote in news:3a8cbb2e.0407021131.55805361 > > @posting.google.com: [quoted text clipped - 5 lines] > The metadata bit of this seems to suggest that in future releases of > java, you'll be able to generate actual source code on the fly. I think the metadata is for hints for documentation generation. I could be wrong. But I'd hate to work out a security system for Java if they allow the code to modify itself. Dynamically extending classes is plenty. Thanks for all the help. Japcuh (Just Another Perl C Unix Hacker) http://www.catb.org/~esr/faq/hacker-howto.htm#what_is .0. ..0 000 No, but this could be done in Smalltalk blind folded. > How do you write self modifying code in Java? > [quoted text clipped - 4 lines] > ..0 > 000 >No, but this could be done in Smalltalk blind folded. > >> How do you write self modifying code in Java? Is it a problem that you sometimes do it accidentally? SignatureCanadian Mind Products, Roedy Green. Coaching, problem solving, economical contract programming. See http://mindprod.com/jgloss/jgloss.html for The Java Glossary. > No, but this could be done in Smalltalk blind folded. You can use Java Reflection which is Java's counterpart to Smalltalk's perform: concatenate some strings to create an existing method name and call that method. Or you can use the command pattern and add commands as required to a list and execute them sequentially. Cheers, Oliver > > How do you write self modifying code in Java? > > [quoted text clipped - 4 lines] > > ..0 > > 000 Check out this package: http://jakarta.apache.org/bcel/ > How do you write self modifying code in Java? > [quoted text clipped - 4 lines] > ..0 > 000 > How do you write self modifying code in Java? > [quoted text clipped - 4 lines] > ..0 > 000 It's nowhere near as easy as it is in Perl. If you look at JDBC you'll see that there's a call to Class.forName() to load the driver class. That may be of use to you. It's sort of an 'import' on the fly. > How do you write self modifying code in Java? > [quoted text clipped - 4 lines] > ..0 > 000 Look up "Javassist" on google. Its what JBoss 4.0 uses to do dynamic aspect weaving and dynamic remote proxy generation among other things. By the way, for those who have used cglib, can you point toward some good online docs? I have been unable to find any I found adequate. Javassist has pretty good docs however. l8r, Mike N. Christoff japcuh@gmail.com wrote... > How do you write self modifying code in Java? If it's truly self-modifying, good luck debugging it. Entropy <entropy@domain.invalid> scribbled on the stall wall: > japcuh@gmail.com wrote... >> How do you write self modifying code in Java? > > If it's truly self-modifying, good luck debugging it. the simple answer is "you can't"...self modifying code hasn't really been feasible since the fortran 4 days...or maybe in C but that is still platform dependent. noone@uber.usachoice.net wrote... > Entropy <entropy@domain.invalid> scribbled on the stall wall: > > japcuh@gmail.com wrote... [quoted text clipped - 5 lines] > feasible since the fortran 4 days...or maybe in C but that is still > platform dependent. I recall the capacity of LISP-like functional languages (ie, Scheme) to dynamically generate new functions and apply them. It was a long time ago when I sat in that class, however, and I've never used such a language outside of the classroom. > Entropy <entropy@domain.invalid> scribbled on the stall wall: > [quoted text clipped - 7 lines] > feasible since the fortran 4 days...or maybe in C but that is still > platform dependent. Java "modifies itself" every time it loads a new class definition. An important point is that the decision to load a class is made at run time, not at a "link time." A Java program can even generate an array of bytecodes at run time, turn them into a class, and create objects of that class; see defineClass() in java.lang.ClassLoader. SignatureEric.Sosman@sun.com Free MagazinesGet these publications absolutely FREE for up to 12 months. 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