Custom Annotation :: inject object at runtime

Question

I would like develop a custom annotation to inject object at runtime. The annotation will work as follows
1. develop ValidatorClass annotation on type.
2. If annotated on a type object will be created at runtime and injected to the object. e.g. in class A it will inject validatorimpl object to vald object/
Please let me know how to implement that.
package com.debopam.validate
public interface validator{
public String validate();
package com.debopam.validate
public class validatorimpl implements validator{
public String validate(){
   return "true";
pckage com.debopam
public class A{
@ValidatorClass(name="com.debopam.validate.validatorimpl")
validator vald;
}

Answer 1

yogeshd,
It might be that the .class file for the annotation that you are compiling against is the one you have given us the source code for above, but when you run the program, the class file for the annotation is not the same, and is one that was compiled before you added the static field.
This can happen if your classpath is wrong. (and would explain why the problem only occurs sometimes - because it is only failing when the classpath is wrong).
If you run the following program with the Fully qualified name of your annotation as the argument, and with the same classpath as you run your program, it can tell you where it is finding the annotation class file. Check that this is the same one that you are compiling to.
class WhereLoaded {
    public static void main(String[] args) {
        Class theClass=null;
        if(args.length > 0) {
            try {
                theClass=Class.forName(args[0]);
            } catch (Exception e) {
                e.printStackTrace();
                theClass=Object.class;
        } else {
            System.out.println(
                "The first argument should be a fully qualified class name," +
                " using java.lang.Object instead"
            theClass=Object.class;
        String name=theClass.getName();
        name=name.substring(name.lastIndexOf(".")+1) + ".class";
        System.out.println(name + " loaded from " + theClass.getResource(name));
}regards
Bruce