Can I instrument CodeConverter at runtime?
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.
