code: public String getRequiredParameter(String name) throws GuacamoleException {
  
          // Pull requested parameter, aborting if absent
          String value = getParameter(name);
          if (value == null)
              throw new GuacamoleClientException("Parameter \"" + name + "\" is required.");
  
          return value;
  
      }
docs: Returns the value of the parameter having the given name, throwing an
  exception if the parameter is missing.
  
  @param name
  The name of the parameter to return.
  
  @return
  The value of the parameter having the given name.
  
  @throws GuacamoleException
  If the parameter is not present in the request.