code: public boolean readOnlyRequest( final String requestId ) {
          if ( !_blacklist.containsKey( requestId ) ) {
              if ( _log.isDebugEnabled() ) {
                  _log.debug( "Registering readonly request: " + requestId );
              }
              incrementOrPut( _readOnlyRequests, requestId );
              return true;
          }
          return false;
      }
docs: Registers the given requestURI as a readonly request, as long as it has not been tracked
  before as a modifying request (via {@link #modifyingRequest(String)}).
  <p>
  There's a limit on the number and the time readonly requests are beeing stored (simply a LRU cache),
  so that the most frequently accessed readonly requests are stored.
  </p>
  @param requestId the request uri to track.
  @return <code>true</code> if the requestURI was stored as readonly, <code>false</code> if it was on the blacklist.
  @see #modifyingRequest(String)