code: public static String getValueFromStaticMapping(String mapping, String key) {
      Map<String, String> m = Splitter.on(";")
          .omitEmptyStrings()
          .trimResults()
          .withKeyValueSeparator("=")
          .split(mapping);
      return m.get(key);
    }
docs: Gets the value with a given key from a static key/value mapping in string format. E.g. with
  mapping "id1=user1;id2=user2", it returns "user1" with key "id1". It returns null if the given
  key does not exist in the mapping.
  
  @param mapping the "key=value" mapping in string format separated by ";"
  @param key the key to query
  @return the mapped value if the key exists, otherwise returns ""