private void putParameterIfAbsent(String name, String value) {
    if (parameters.containsKey(name)) {
      throw new IllegalStateException("Invalid attempt to overwrite a read-only parameter: " + name);
    }

    parameters.put(name, value);
  }
Put a parameter to the listener event only if the parameter is absent.

Overridden parameters is not allowed, and an exception may be thrown to avoid a mis-configuration
between listeners setting the same parameters.

@param name Name of the parameter.
@param value Value of the parameter.
@throws IllegalStateException if a parameter already exists.
standalone-metastore/metastore-server/src/main/java/org/apache/hadoop/hive/metastore/events/ListenerEvent.java