[jboss-user] [Javassist] New message: "Re: determining if code passed to insertAfter() is executed after an exception handler or before normal return"
User development,
A new message was posted in the thread "determining if code passed to insertAfter()
is executed after an exception handler or before normal return":
http://community.jboss.org/message/526689#526689
Author : Arvind K
Profile : http://community.jboss.org/people/megalodon
Message:
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I didnt know much about CtMethod.instrument() and ExprEditor and its edit methods before.
You can use them to solve the above problem:
// Suppose you want to know from where the insertBefore code of 'myCtMethod' is
running, You can add a boolean
// variable to the class for this purpose (unfortunately, we need one for every such
method). In our case, I call
// it 'inHandler'. Set it to false upon initialization.
myCtMethod.instrument(new ExprEditor() {
public void edit(Handler myHandler) throws CannotCompileException {
try {
// insertBefore inserts the statement before the catch block is entered. You can even
change the exception here, i think.
// Here I set inHandler to true signifying entry into the catch block.
myHandler.insertBefore("inHandler = true;"); // inHandler is an (added)
field of the CtClass containing myCtMethod
// Below statement prints some description of the handler object, if needed.
myHandler.insertBefore("System.out.println(\"Instrumentation detected
presence of a Handler for " + myHandler.getType().getName() + " at line number
" + myHandler.getLineNumber()+"\");");
} catch (NotFoundException ntfnde) {
ntfnde.printStackTrace();
}
}
});
// The below if statement will distinguish between normal code and exception handler code
and execute accordingly
sayCtM.insertAfter("if (inHandler == true) System.out.println(\"Running within
a handler.\"); else System.out.println(\"Running in normal
code\");");
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