code: public SipURI createSipURI(String user, String host) {		
  		if (logger.isDebugEnabled()) {
  			logger.debug("Creating SipURI from USER[" + user + "] HOST[" + host
  					+ "]");
  		}		
  		// Fix for http://code.google.com/p/sipservlets/issues/detail?id=145
  		if(user != null && user.trim().isEmpty()) {
  			user = null;
  		}
  		try {
  			return new SipURIImpl(SipFactoryImpl.addressFactory.createSipURI(
  					user, host), ModifiableRule.Modifiable);
  		} catch (ParseException e) {
  			logger.error("couldn't parse the SipURI from USER[" + user
  					+ "] HOST[" + host + "]", e);
  			throw new IllegalArgumentException("Could not create SIP URI user = " + user + " host = " + host);
  		}
  	}
docs: /*
  (non-Javadoc)
  
  @see javax.servlet.sip.SipFactory#createSipURI(java.lang.String,
  java.lang.String)