Red Hat
Dec 5, 2012
by noreply@blogger.com (Andrew Dinn)
Byteman 2.1.2 is now available for download. You can obtain a copy either as a binary-only or full-source zip from the project downloads page or you can depend upon the version available in the Maven Central repository.

Byteman 2.1.2 is for the most part a maintenance update to release 2.1.0, fixing about half a dozen bugs. However, it does include a few new features. In particular:
  • Allow downcasts when initialising local vars in the BIND clause
  • Support computing object size as a standard method in Helper
Downcasting is particularly helpful when dealing with generic types when you know that a specific type parameter is used. For example when injecting into this class

class Foo
{
void foo(List names)
. . .
}

downcasting allows you to bind elements of the argument list using the type String rather than the generic type Object

RULE access name as a name
CLASS Foo
METHOD foo
BIND first : String = $names.get(0);
second : String = $names.get(1);
IF first == "Andrew" && second == "Dinn"
DO throw new Exception("Won't get fooed again!")
ENDRULE

Of course, Byteman performs a checkcast before binding the variables so when the rule executes if you try to downcast a value which is not an instance of the subtype your program will see a ClassCastException.

If you want to disable downcasting and revert to the old behaviour where the type checker flags this as a type error the simply set system property

    org.jboss.byteman.disallow.downcasts

 in the JVM running the Byteman agent.
Original Post