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List:       bcel-user
Subject:    Re: Exception Handling
From:       Andrew Huntwork <ash () huntwork ! net>
Date:       2004-08-09 14:15:58
Message-ID: 4117871E.8000808 () huntwork ! net
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yeah, that looks generally fine.  maybe you could post the code that 
adds the exceptions and/or the "mangled" bytecode

Irving, Dave wrote:
> Hi,
> 
> I've used BCEL a while ago to create **new** classes on the fly, but am
> getting stuck on something I've never had to do before: Inserting
> instructions to existing classes.
> Im trying to wrap each method in a class with a
> try/catch(NullPointerException).
> So this method:
> 
> public int getInt() {
> return getIntFromSomewhere();
> }
> 
> would become:
> 
> public int getInt() {
> try {
> return getIntFromSomewhere();
> }
> catch(NullPointerException e) {
> // do something
> return 0;
> }
> }
> 
> Im not having much luck at the moment - my current approach is this:
> 
> 1) Use the methods InstructionList.getStart() to get the first instruction
> 2) Use InstructionList.getEnd() to get the last instruction
> 3) Add exception handling code (keeping an InstructionHandler to the first
> instruction in the handling code)
> 4) Add an appropriate return (using InstructionFactory.createNull ) if
> return type is not void
> 5) Add an exception handler to the method, using start and end obtained from
> 1/2 above, and the instruction handle obtained in 3 as the exception
> handling code handle
> 
> Does this seem like a reasonable approach? Currently the methods produced
> seem to be completely mangled - so Im guessing Im way out on something -
> maybe one of my assumptions above.
> Any advice would be greatly appreciated!
> 
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