[jboss-user] [Javassist user questions] - Can I instrument CodeConverter at runtime?

[dodomio]

Hi everybody,

I'm trying to modify a method of my custom CodeConverter at runtime, as the instrumentation is based on the content of a configuration file. I'm stuck at the error You can see below.

Actually I wrote this:

  | public class Main {
  | 
  | 	public static void main(String[] args) throws Throwable {
  | 
  |         ClassPool cp = ClassPool.getDefault();
  |         Loader loader = new Loader(Main.class.getClassLoader(),cp);
  | 
  | 	// Get the class and instrument
  | 	CtClass conv = cp.get("pkg.CustomConverter");
  | 	CtMethod m = conv.getDeclaredMethod("init");
  | 	StringBuffer sb = new StringBuffer();
  | 	sb.append("{\n");
  | 	sb.append("CtMethod m1 = thePool.get(\"pkg.Hello\").getDeclaredMethod(\"say\");\n");
  | 	sb.append("CtMethod m2 = thePool.get(\"pkg.Hello\").getDeclaredMethod(\"first\");\n");
  | 	sb.append("insertBeforeMethod(m1, m2);\n");
  | 	sb.append("}\n");
  | 	m.setBody(sb.toString()); // (*) Here I got the error shown below
  |         
  |         CustomConverter conv = (CustomConverter) conv.toClass().newInstance();
  |         CustXlator xlat = new CustXlator(conv);
  | 
  |         loader.addTranslator(cp, xlat);
  |         loader.run(args);			// Loads and runs the class pkg.Hello
  | 	}
  | 
  | }
  | 

CustXlator's onLoad method does simply:

  | 		if (className.equals("pkg.Hello")) {
  | 			CtClass c = pool.get(className);
  | 			c.instrument(converter);
  | 			// converter is an instance of CustomConverter passed as
  | 			// the only parameter to CustXlat constructor
  | 		}
  | 
while CustomConverter has only the init method that I'm trying to instrument.

I'm stuck at an exception occourring during setBody execution. The stacktrace is:

  | javassist.CannotCompileException: [source error] no such class: CtMethod
  | 	at javassist.CtBehavior.setBody(CtBehavior.java:346)
  | 	at javassist.CtBehavior.setBody(CtBehavior.java:315)
  | 	at pkg.Main.main(Main.java:29)
  | Caused by: compile error: no such class: CtMethod
  | 	at javassist.compiler.MemberResolver.searchImports(MemberResolver.java:416)
  | 	at javassist.compiler.MemberResolver.lookupClass(MemberResolver.java:392)
  | 	at javassist.compiler.MemberResolver.lookupClassByJvmName(MemberResolver.java:310)
  | 	at javassist.compiler.MemberResolver.resolveJvmClassName(MemberResolver.java:460)
  | 	at javassist.compiler.MemberCodeGen.resolveClassName(MemberCodeGen.java:1064)
  | 	at javassist.compiler.CodeGen.atDeclarator(CodeGen.java:698)
  | 	at javassist.compiler.ast.Declarator.accept(Declarator.java:99)
  | 	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:344)
  | 	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
  | 	at javassist.compiler.CodeGen.atStmnt(CodeGen.java:344)
  | 	at javassist.compiler.ast.Stmnt.accept(Stmnt.java:49)
  | 	at javassist.compiler.CodeGen.atMethodBody(CodeGen.java:285)
  | 	at javassist.compiler.Javac.compileBody(Javac.java:212)
  | 	at javassist.CtBehavior.setBody(CtBehavior.java:340)
  | 	... 2 more
  | 

It seems that CustomConverter was unable to resolve CtMethod class!!!
But if I statically modify the init method all is ok.

I really don't know how to solve the problem.
Can someone help me? I'll appreciate it very much!

Thanks in advance, Mauro.

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