The BRM REST Services Manager framework uses Jakarta Expression Language (EL) for mapping and transformation, supporting both standard and user-defined functions. You can extend mapper expressions by adding custom expression functions in ExtendedMapperExpressionUtil.java, located in the SDK package under mapper/extension/utils.

Custom expression functions allow you to access important objects such as:

• context: A list of payload objects representing the hierarchy, which is a List<JsonNode> during request processing and a List<FList> during response processing.

• rootContext: The complete payload or flist object, available as a JsonNode during requests and as an FList during responses.

Use these custom functions in your expression mappings to implement advanced data transformations.

See "Mapper Features" in BRM Installation Guide for more information.