Messages metadata file is used to define the error, question, and informational messages used by the system. This section describes how custom messages can be defined. For more information on creating new messages, please go to Implement Messages.
What does this section cover?
Messages File
Custom messages are declared in messages.xml file, which must be created under <custom_project>/web/WebContent/metadata directory.
Define Custom Messages
To define a custom error, question or informational message you have to use a unique message code and define the message expression and description.
For the expression value, you must use a key. For more information on how to use glossary mechanism implementing messages, go to go to Use Glossary Mechanism - Exceptions / Questions / Informational Messages
In the following example, a new error message is defined