A Comprehensive Guide to the NestJS Request-Response Lifecycle
Introduction The Request-Response Lifecycle in NestJS is a clearly defined sequence of steps that a request must pass through before a response is sent back to the client. Simply put, it is like a production line: each department has its own task to check, transform, or process the data. Key Components The typical execution order is as follows: Incoming Request: The request sent from the client. Middleware: Performs tasks such as logging, basic authentication, or modifying the request object. Guards: Responsible for security, deciding whether this request is allowed to proceed (Authentication/Authorization). Interceptors (Pre-controller): Allows you to intervene in the logic before it reaches the Controller. Pipes: Used for data transformation (Transformation) and validating the input data (Validation). Controller: Where the main business logic resides and processes the request. Interceptors (Post-controller): Processes the data after the Controller returns it (e.g., changing the JSON ...