public String setProperty(String configType, String propertyName, String value) {
    String previousValue = getPropertyValue(configType, propertyName);
    Map<String, String> typeProperties = properties.get(configType);
    if (typeProperties == null) {
      typeProperties = new HashMap<>();
      properties.put(configType, typeProperties);
    }
    typeProperties.put(propertyName, value);
    return previousValue;
  }
Set a property on the configuration.
The property will be set on this instance so it will override any value specified in
the parent hierarchy.

@param configType    configuration type
@param propertyName  property name
@param value         property value

@return the previous value of the property or null if it didn't exist
ambari-server/src/main/java/org/apache/ambari/server/topology/Configuration.java