code: @Override
  	public String getURLPrefix(Map<String, String> variants) {
  
  		if (null == this.urlPrefix)
  			throw new IllegalStateException("The bundleDataHashCode must be set before accessing the url prefix.");
  
  		if (variants != null && !variants.isEmpty()) {
  			String key = getAvailableVariant(variants);
  			if (StringUtils.isNotEmpty(key)) {
  				return prefixMap.get(key) + "." + key + "/";
  			}
  		}
  		return this.urlPrefix + "/";
  	}
docs: /*
  (non-Javadoc)
  
  @see
  net.jawr.web.resource.bundle.JoinableResourceBundle#getURLPrefix(java
  .util.Map)