Is it possible to construct a snippet of code in Java that would make a hypothetical java.lang.ChuckNorrisException
uncatchable?
Thoughts that came to mind are using for example interceptors or aspect-oriented programming.
17 s
I haven’t tried this, so I don’t know if the JVM would restrict something like this, but maybe you could compile code which throws ChuckNorrisException
, but at runtime provide a class definition of ChuckNorrisException
which does not extend Throwable.
UPDATE:
It doesn’t work. It generates a verifier error:
Exception in thread "main" java.lang.VerifyError: (class: TestThrow, method: ma\
in signature: ([Ljava/lang/String;)V) Can only throw Throwable objects
Could not find the main class: TestThrow. Program will exit.
UPDATE 2:
Actually, you can get this to work if you disable the byte code verifier! (-Xverify:none
)
UPDATE 3:
For those following from home, here is the full script:
Create the following classes:
public class ChuckNorrisException
extends RuntimeException // <- Comment out this line on second compilation
{
public ChuckNorrisException() { }
}
public class TestVillain {
public static void main(String[] args) {
try {
throw new ChuckNorrisException();
}
catch(Throwable t) {
System.out.println("Gotcha!");
}
finally {
System.out.println("The end.");
}
}
}
Compile classes:
javac -cp . TestVillain.java ChuckNorrisException.java
Run:
java -cp . TestVillain
Gotcha!
The end.
Comment out “extends RuntimeException” and recompile ChuckNorrisException.java
only :
javac -cp . ChuckNorrisException.java
Run:
java -cp . TestVillain
Exception in thread "main" java.lang.VerifyError: (class: TestVillain, method: main signature: ([Ljava/lang/String;)V) Can only throw Throwable objects
Could not find the main class: TestVillain. Program will exit.
Run without verification:
java -Xverify:none -cp . TestVillain
The end.
Exception in thread "main"