The RXTX Library from http://rxtx.qbang.org is available via Maven Repository. But handling the native libraries which are not part of the maven artifact is still a mess. So here comes the solution:
"RXTX rebundled" contains all required files and loads the correct native library (64bit Windows DLL is also available) automatically. The RXTX API has not changed. The automatic library loading is totally transparent to you. Just forget about "java.library.path".