Reflection Sample - Whats wrong in this?
Please find the below code.
public class FiledRef {
public static void main(String[] args) {
try{
Class clas = null;
clas = Class.forName("fieldRef.TwoString");
System.out.println("VALUE IS -> "+incrementField("val02",clas));
}catch(Exception ex){
ex.printStackTrace();
}
}
public static int incrementField(String name, Object obj) throws Exception{
Field field = obj.getClass().getDeclaredField(name);
int value = field.getInt(obj) + 1;
field.setInt(obj, value);
return value;
}
}
I have another class TwoString, which contains an int variable val02, which has a value 10.
When I tried the above code for Reflection, I got the compilation Error as java.lang.NoSuchFieldException: val02. Canb you please tell me where I have gone wrong? Can anyone help me to sort it out.....?
[901 byte] By [
JayKay007a] at [2007-11-27 10:04:00]
# 3
As always, I am a bit short with my answer, but I want to add something: If "val02" refers to a static variable of your TwoString, you must not get declared fields from obj.getClass() but pass in the class and get the class's fields. In your case, obj.getClass() will return Class.
# 4
> As always, I am a bit short with my answer, but I
> want to add something: If "val02" refers to a static
> variable of your TwoString, you must not get declared
> fields from obj.getClass() but pass in the class and
> get the class's fields. In your case, obj.getClass()
> will return Class.
Huh? You always query a class object for fields, regardless of whether the field is static or not. If you're reflectively invoking a static member, you pass in null in place of the object upon which to invoke
# 5
> Huh? You always query a class object for fields,
> regardless of whether the field is static or not. If
> you're reflectively invoking a static member, you
> pass in null in place of the object upon which to
> invoke
Sure. But you shouldn't call getDeclaredMethod() on obj.getClass() if obj is the class already (as it is passed to incrementField() in the OP).
# 7
Maybe my comment is too confusing and missing the OP's goal, which does not state, whether it is an instance variable or a class variable (for the latter you would not need an instance of TwoString, that's all I wanted to state).
So let's assume it's an instance variable. In this case, necessitating an instance of TwoString is correct.
