package javax.jnlp is declared in module java.jnlp, which is not in the module graph

I have a project that uses Java webstart technology. I decided to upgrade the Java version from 8 to 9. However, I faced the following error on compiling:

error: package javax.jnlp is not visible
import javax.jnlp.DownloadServiceListener;
        ^
(package javax.jnlp is declared in module java.jnlp, which is not in the module graph)

I tried to include C:\Program Files\Java\jdk-9\lib\javaws.jar to the classpath, but still the same issue remains.