This document provides detailed information on how structured error messages are generated in Commerce Engine and made consumable by end users. For a general overview of structured messages are and how they are work, see Structured Messages in the Touchpoint Developer's Guide.

Structured error messages go through a number of transformations from their generation in Commerce Engine through to being presented to the user. A structured message goes through three transformations: one in Commerce Engine and two in Cortex. Separating the transformations allows for the separation of data between Commerce Engine, Cortex and the client browser.

In general, structured error messages are generated through the creation of constraint violations and invalid business states in Commerce Engine. These violations are then transformed into a set of com.elasticpath.common.dto.StructuredErrorMessage objects. Commerce Engine then generates an exception which returns both an exception message and the set of StructureErrorMessage objects and passes these to Cortex.

In Cortex, the set of StructuredErrorMessage objects are then extracted from the exception and passed into another transformer, which then transforms the objects into com.elasticpath.rest.advise.Message objects. This transformation replaces the Commerce Engine field names with front-end field names understandable by the client. To see which error message codes map to which responses, see the API Reference.

After the second transformation, the resulting structure is attached to an execution result. The execution result moves up and is converted to an operation result. The final transformation is from Message to com.elasticpath.schema.StructuredMessage occurs in this stage. StructuredMessage enriches the standard JSON response of Message, providing additional information and fields, such as the linked-to and blocks fields.