code: public void setContentType(String type) {
  		checkContentType(type);
  		checkCommitted();
  		String name = getCorrectHeaderName(ContentTypeHeader.NAME);
  		try {
  			Header h = SipFactoryImpl.headerFactory.createHeader(name, type);
  			this.message
  					.removeHeader(getCorrectHeaderName(ContentTypeHeader.NAME));
  			this.message.addHeader(h);
  		} catch (ParseException e) {
  			logger.error("Error while setting content type header !!!", e);
  		}
  
  	}
docs: /*
  (non-Javadoc)
  @see javax.servlet.sip.SipServletMessage#setContentType(java.lang.String)