javac task question

I know of a couple of ways to run javac on more than one source tree.

One way is to use nested src elements.

Another way is like this:

srcdir=3D"${src}:${src2}=E2=80=9D

I would like to generalize this solution to a dynamicly determined list =
of source trees.

I thought that I could use srcpath for this purpose, but the task would =
fail if srcdir was not specified or it did not identify a valid =
directory.
That restriction defeats my purpose.

Is there a solution?

Is the inability to use srcpath by itself a bug?

Thank you.