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API / Apache Grails Interview questions

Explain the lifecycle of a request in a Grails application?

A request in Grails passes through several layers built on top of the underlying Spring Boot/servlet stack before a response is generated, with Grails' own conventions handling most of the routing and rendering decisions along the way.

flowchart TD A[Incoming HTTP request] --> B[Servlet container / Spring Boot dispatcher] B --> C[Grails UrlMappings resolves URL to controller/action] C --> D{Custom URL mapping exists?} D -- Yes --> E[Use explicit mapping] D -- No --> F[Use default convention: /controller/action] E --> G[Instantiate/reuse controller, bind params] F --> G G --> H[Any configured interceptors run before the action] H --> I[Controller action executes, typically delegating to services] I --> J{Action returns model / calls render or redirect?} J -- Render view --> K[Resolve matching GSP by convention] K --> L[GSP rendered to HTML] J -- Render JSON/other --> M[Serialize response directly] L --> N[Any configured interceptors run after the action] M --> N N --> O[Response sent to client]

The request first passes through Spring Boot's own dispatching machinery, then Grails' UrlMappings resolve which controller and action should handle it, either via an explicit mapping or the default convention. Before the action itself runs, any configured interceptors get a chance to inspect or short-circuit the request (for things like authentication checks), and after the controller action executes — typically by delegating real work to a service — Grails resolves and renders the matching GSP view (or serializes a direct response for a REST-style action) before interceptors run again on the way out and the final response is sent.

This layered structure is what lets Grails add its own conventions (URL mapping, view resolution, interceptors) cleanly on top of the standard servlet request lifecycle rather than replacing it outright.

At what point in the request lifecycle do configured interceptors first get a chance to run?
What determines which GSP file gets rendered after a controller action completes, when no explicit view is specified?

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