Libra provides the means to weigh your Objects.
long myObjectSize = Libra.getObjectSize("Hello world");
That's it. No more.
There are two ways to boot up Libra.
java -javaagent:jboss-libra.jar MyMain
Libra will be initialized through the Java Agent mechanism.
java -cp $JAVA_HOME/lib/tools.jar MyMain
Libra will initialize itself through the Attach API.
For usage in AS 7 please refer to How-To: use Libra in AS 7.