I've found a solution, using patternset.
<patternset id="ps1"> <include name="source1\**" /> </patternset>
<patternset id="ps2"> <include name="source2\**" /> </patternset>
<javac ...>
<patternset>
<patternset refid="ps1" />
<patternset refid="ps2" />
</patternset>
</javac>