How to catch all checked exceptions (in a single block) in Java?

If I understood correctly, then you are almost there. Just catch RuntimeException. That will catch RuntimeException and everything under it in the hierarchy. Then a fallthrough for Exception, and you're covered:

try {
    transaction.commit();
} catch (RuntimeException e) {
    // Throw unchecked exception
    throw e;
} catch (Exception e) {
    // Handle checked exception
    // ...
}

Java 7 allows you such constructions:

try {
    transaction.commit();
} catch (SecurityException | IllegalStateException  | RollbackException | HeuristicMixedException  e ) {
   // blablabla
}

UPD: I think, that there isn't nice and convenient way for doing it in earlier versions of Java. That is why developers of Java language introduced such construction in Java 7. So, you could devise your own approaches for Java 6.