Master Spring MVC: Core Concepts, Annotations, and Interceptor Guide

1. What is MVC?

MVC is a design pattern that separates software into three layers: Model (data), View (user interface), and Controller (business logic). The Controller acts as a bridge between Model and View, reducing coupling and facilitating maintenance.

2. What does the DAO layer do?

DAO (Data Access Object) is a dedicated layer for database access. Common implementations in Spring include Spring JDBC, Hibernate, JPA, and MyBatis. Regardless of the technology, the programming model remains consistent within the Spring framework.

3. Spring MVC execution flow

The process starts when a client sends an HTTP request that matches the DispatcherServlet mapping; the web container forwards the request to DispatcherServlet.

DispatcherServlet uses HandlerMapping to locate the appropriate handler based on the request information (URL, method, headers, parameters, etc.). Any object can serve as a handler.

The located handler is wrapped by a HandlerAdapter, which invokes the handler through a uniform interface.

After processing, the handler returns a ModelAndView containing the logical view name and model data.

ViewResolver resolves the logical view name to a concrete View object.

DispatcherServlet uses the View to render the model data.

The client receives the response, which may be HTML, XML, JSON, an image, a PDF, etc.

4. Common Spring MVC annotations

@RequestMapping : Maps request URLs to controller methods. Attributes include method (GET, POST, etc.), value (URL patterns), produces , consumes , headers , and params .

@RequestParam : Binds request parameters to method arguments. Attributes: value (parameter name) and required (default true).

@RequestBody : Indicates that the method return value should be written directly to the HTTP response body, typically used for asynchronous data retrieval. Attribute: required (default true).

@PathVariable : Binds URL placeholders to method parameters, enabling REST‑style URLs in Spring MVC.

5. Spring MVC interceptors

Interceptors implement the HandlerInterceptor interface, providing preHandle(), postHandle(), and afterCompletion() methods.

Execution flow:

preHandle() runs first; returning false aborts the request.

The handler processes the request.

postHandle() runs after handler execution.

View resolution and rendering occur.

afterCompletion() runs after the request is fully completed.

Development steps:

Implement HandlerInterceptor and define the desired logic in the appropriate methods.

Register the interceptor by creating a configuration class that implements WebMvcConfigurer and overrides addInterceptors to specify path patterns.

6. How to perform request interception

Use a Spring MVC interceptor for controller‑level interception.

Use a Filter to intercept all requests, including static resources.

Use Spring AOP to intercept calls to beans other than controllers.