Admonish
A simple validation library for app services and domain entities.
Usage
See introduction.
Motivation
Sometimes validation logic is duplicated
- in application services, where a special kind of exception is thrown that is converted to a 400 HTTP response,
- and in domain entities, where preconditions are checked according to the usual OOP practice to keep the class state consistent. An ArgumentException or a sublcass of it is usually thrown in this case.
The idea behind this library is to throw that "special kind of exception" from entities without referring to it explicitly, allowing one to remove duplication and keep entity-related validation only in entities.
Highlights
Focus on primitive values
Because in domain entities one doesn't usually have access to DTOs Admonish is focused on validating privitive values, not DTOs, unlike most other libraries.
Although some methods are provided to validate complex objects, such usage is discouraged.
Error accumulation
Admonish accumulates errors until ThrowIfInvalid() is called. This is in contrast to the approach taken in some other libraries that throw an exception immediately on the first error encounterd.
Extensibility
Users can write their own extension methods to the ValidationResult class to create custom named
validation rules, e.g. CheckCreditCard.
Customization
Users can substitute the type of exception thrown on validation errors (see the UnsafeConfigureException method) making domain validation code throw a custom exception (defined e.g. in a web infrastructure library) without "knowing" about it.
Simplicity
The code and the API of the library are kept as simple as possible.