In the context of protovalidate, "constraints" refer to the conditions or
requirements that the data fields within a Protobuf message must meet. These
constraints are defined by developers using the provided custom option
annotations to help ensure that the data is semantically valid.
Constraints can be applied to Protobuf messages, their fields, and oneof unions.
In protovalidate, constraints are defined using the provided syntax or
custom expressions within the Protobuf message definition. At runtime, when the
Protobuf message is passed to the library, it checks whether the input data
meets the specified constraints. If the data fails to meet the constraints, a
series of validation
violations are raised in an error, indicating the issue with the input data.
Constraints fall into 2 categories:
These options supplied by protovalidate are used
to define validation rules and constraints for individual fields in a Protobuf
message. These options include specifications for field types, minimum and
maximum values, regular expressions, and custom validation functions.
To understand all of the standard constraints available in protovalidate, see
the Standard Constraints page.
These field-level and message-level options are defined by the user and used to define custom validation rules and constraints in a Protobuf message. They are defined using the Common Expression Language (CEL) and enable complex rules and constraints that aren't supported by the standard constraints. They can also reference other fields in the message.
To understand how to define custom constraints in protovalidate, see the
Custom constraints page.