Adding an annotation to a runtime generated method/class using Javassist
- by Idan K
I'm using Javassist to generate a class foo, with method bar, but I can't seem to find a way to add an annotation (the annotation itself isn't runtime generated) to the method. The code I tried looks like this:
ClassPool pool = ClassPool.getDefault();
// create the class
CtClass cc = pool.makeClass("foo");
// create the method
CtMethod mthd = CtNewMethod.make("public Integer getInteger() { return null; }", cc);
cc.addMethod(mthd);
ClassFile ccFile = cc.getClassFile();
ConstPool constpool = ccFile.getConstPool();
// create the annotation
AnnotationsAttribute attr = new AnnotationsAttribute(constpool, AnnotationsAttribute.visibleTag);
Annotation annot = new Annotation("MyAnnotation", constpool);
annot.addMemberValue("value", new IntegerMemberValue(ccFile.getConstPool(), 0));
attr.addAnnotation(annot);
ccFile.addAttribute(attr);
// generate the class
clazz = cc.toClass();
// length is zero
java.lang.annotation.Annotation[] annots = clazz.getAnnotations();
And obviously I'm doing something wrong since annots is an empty array.
This is how the annotation looks like:
@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface MyAnnotation {
int value();
}
