How do I override Class<?>.getName() for certain classes? - aop

Question

My goal is to be able to override what I get back from CustomClass.class.getName() and CustomClass.getClass().getName()
It should return a custom value, which I think is best to define in an attribute like
#NameOverride("Custom.fully.qualified.class.name")
public class CustomClass {}
Is there any way to do that?

Answer 1

Fred's answer is okay, but his aspect could be somewhat more elegant with less code and especially fewer reflection calls. Sorry, I prefer AspectJ native code style, but #AspectJ annotation style would not be much longer:
String around(Class clazz) : call(public String Class.getName()) && target(clazz) {
NameOverride nameOverride = (NameOverride) clazz.getAnnotation(NameOverride.class);
return nameOverride == null ? proceed(clazz) : nameOverride.value();
}
Here is the full source code. I added a class without annotation to show the different behaviour and also a restriction to class definitions - #Target(ElementType.TYPE) - to the annotation class. I am also showing package names and imports:
package test;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
#Retention(RetentionPolicy.RUNTIME)
#Target(ElementType.TYPE)
public #interface NameOverride {
String value();
}
package test;
public class NormalClass {}
package test;
#NameOverride("Custom.fully.qualified.class.name")
public class CustomClass {}
package test;
public class Main {
public static void main(String[] args) {
System.out.println(NormalClass.class.getName());
System.out.println(CustomClass.class.getName());
System.out.println(new NormalClass().getClass().getName());
System.out.println(new CustomClass().getClass().getName());
}
}
package aspectj;
import test.NameOverride;
public aspect GetNameOverrider {
#SuppressWarnings({ "unchecked", "rawtypes" })
String around(Class clazz) : call(public String Class.getName()) && target(clazz) {
NameOverride nameOverride = (NameOverride) clazz.getAnnotation(NameOverride.class);
return nameOverride == null ? proceed(clazz) : nameOverride.value();
}
}
The output:
test.NormalClass
Custom.fully.qualified.class.name
test.NormalClass
Custom.fully.qualified.class.name

Answer 2

This is for sure not the best/fastest solution but maybe a POC...
First of all the file structure:
./src/aspectj:
GetNameOverrider.aj
./src/test:
CustomClass.java Main.java NameOverride.java
NameOverride.java:
#Retention(RetentionPolicy.RUNTIME)
public #interface NameOverride {
String value();
}
GetNameOverrider.aj:
#Aspect
public class GetNameOverrider {
#Around("call(String getName()) && !within(aspectj..*)")
public String advice(ProceedingJoinPoint pjp) throws Throwable {
String ret = (String) pjp.proceed();
String className = "" + pjp.getTarget();
className = className.replace("class ", "");
try {
test.NameOverride anno = Class.forName(className).getAnnotation(
test.NameOverride.class);
if (anno != null) {
return anno.value();
}
} catch (ClassNotFoundException e) {
return ret;
}
return ret;
}
}
gives me for Main.java:
public class Main {
public static void main(String[] args) {
System.out.println(CustomClass.class.getName());
System.out.println(new CustomClass().getClass().getName());
}
}
the output:
Custom.fully.qualified.class.name
Custom.fully.qualified.class.name