New Project Development Story Integrating with Multiple Partners, Part 2

If the range of user input is not strictly defined, it can lead to unexpected system behavior or degraded data reliability. Therefore, validation must be performed on both the client and server sides in parallel. The client aims to guide users and prevent transmission of invalid data, while the server aims to protect the system and respond to security risks.

Using Kotlin Contracts, you can strengthen validation by conveying information the developer knows to the compiler. Functions like require, check, and requireNotNull internally use contract to help the compiler recognize the state after validation passes (e.g., not null).

Applying this, you can define project-specific custom exceptions. By implementing custom validation functions using contract, you can achieve more sophisticated error handling, such as responding with clear error handling and distinguishing HTTP status codes when specific conditions are not met.

Writing test code increases the reliability of the code and ensures the stability of refactoring. Through unit tests and integration tests, edge cases can be detected, and by verifying that the service operates as intended by the design, the ability to handle exceptional situations is improved.