spring-mvc

Building web applications requires handling HTTP requests, mapping URLs to handlers, parsing parameters, validating input, rendering views, and managing sessions. Without a structured framework, web-tier code becomes a messy mix of request handling, business logic, and presentation.

Spring MVC is a web framework built on the Model-View-Controller pattern, with the DispatcherServlet as the front controller. It cleanly separates concerns: Controllers handle requests, Models hold data, and Views render output. The framework handles request routing, parameter binding, validation, and view resolution transparently.

1. DispatcherServlet: The front controller receives all HTTP requests and delegates to configured components
2. Handler mapping: DispatcherServlet consults HandlerMapping to find which controller method handles the request URL
3. Controller execution: The selected @Controller method executes, processes the request, and returns a ModelAndView
4. View resolution: ViewResolver maps logical view names (e.g., “home”) to actual view templates (home.jsp, home.html)
5. Response rendering: View renders the model data into HTML, JSON, or XML

• Front controller pattern: DispatcherServlet centralizes request handling
• Annotation-based: @Controller, @RequestMapping, @RequestParam, @ModelAttribute
• View technology agnostic: Works with JSP, Thymeleaf, FreeMarker, Mustache
• REST support: @RestController combines @Controller + @ResponseBody for JSON/XML APIs
• Data binding: Automatically binds request parameters to Java objects
• Validation: @Valid + BindingResult for declarative input validation

• Built from: Spring Framework — Spring MVC is built on Spring Core (IoC, DI)
• Built from: DispatcherServlet — The front controller is the entry point of Spring MVC
• Related: Spring Controller — @Controller methods handle specific request mappings
• Builds into: Spring Boot — Spring Boot auto-configures Spring MVC with embedded Tomcat
• Related: Spring Form Handling — Form handling and validation in Spring MVC
• Contrasts with: JSP — JSP is a view technology; Spring MVC is a full web framework

• Hidden HttpMethod: HTML forms only support GET/POST; Spring’s HiddenHttpMethodFilter converts _method=PUT to actual PUT
• @ModelAttribute vs @RequestParam: @ModelAttribute binds complex objects; @RequestParam binds single parameters
• ViewResolver chaining: Multiple ViewResolvers with order priority — first match wins
• async requests: DeferredResult and Callable for long-lived async processing in controllers