code: public void setUser(String user) {
  		if(isModifiable == ModifiableRule.NotModifiable) {
  			throw new IllegalArgumentException("not allowed to set user part, the URI is not modifiable");
  		}
  		try {
  			getSipURI().setUser(user);			
  		} catch (ParseException e) {
  			logger.error("error setting parameter ", e);
  		}
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipURI#setUser(java.lang.String)