Spring MVC

Spring MVC (Model-View-Controller) is a framework within the Spring ecosystem for building web applications. It provides a clean separation of concerns through the MVC design pattern and integrates seamlessly with the core Spring framework for dependency injection, transaction management, and other features. Here’s an overview of Spring MVC, including its key components and features:

Key Components of Spring MVC

  1. DispatcherServlet:

    • Acts as the front controller in the MVC pattern.
    • Receives all incoming HTTP requests and delegates them to the appropriate handlers (controllers).

  2. Controller:

    • Handles user requests and processes user input.
    • Typically annotated with @Controller or @RestController.
    • Uses @RequestMapping or other mapping annotations to map URLs to methods.

  3. Model:

    • Represents the data of the application.
    • Often consists of POJOs (Plain Old Java Objects).
    • Data is added to the model to be passed to the view for rendering.

  4. View:

    • Responsible for rendering the model data.
    • Can be JSP, Thymeleaf, FreeMarker, or other view technologies.
    • View resolvers (like InternalResourceViewResolver) help locate the correct view templates.

  5. ViewResolver:

    • Resolves the logical view names returned by controllers to actual view templates.
    • Configured in the Spring application context.

  6. ModelAndView:

    • A helper class that holds both the model and the view.
    • Returned by controller methods to indicate both the data and the view to render.

How Spring MVC Works

  1. Client Request:

    • A client sends an HTTP request to the server.

  2. DispatcherServlet:

    • The request is received by the DispatcherServlet.
    • The DispatcherServlet consults the HandlerMapping to determine which controller method should handle the request.

  3. Controller:

    • The appropriate controller method is invoked.
    • The controller processes the request, interacts with the service layer if needed, and prepares the model data.

  4. Model and View:

    • The controller returns a ModelAndView object, containing the model data and the view name.

  5. ViewResolver:

    • The DispatcherServlet uses the ViewResolver to resolve the logical view name to an actual view template.

  6. View Rendering:

    • The view template is rendered with the model data and the response is returned to the client.

Key Annotations

  • @Controller: Indicates that a class serves as a web controller.
  • @RequestMapping: Maps HTTP requests to handler methods.
  • @GetMapping, @PostMapping, etc.: Specialized versions of @RequestMapping for specific HTTP methods.
  • @RequestParam: Binds request parameters to method parameters.
  • @PathVariable: Binds URI template variables to method parameters.
  • @ModelAttribute: Binds a method parameter or method return value to a named model attribute.
  • @ResponseBody: Indicates that the return value of a method should be used as the response body.
  • @RestController: Combines @Controller and @ResponseBody, indicating that a class is a RESTful controller.

Pros of Spring MVC

  • Separation of Concerns: Clear separation between controllers, models, and views.
  • Integration: Seamlessly integrates with other Spring components like Spring Security, Spring Data, etc.
  • Flexibility: Supports a wide range of view technologies and can be configured in various ways.
  • Community and Documentation: Well-documented and supported by a large community.

Cons of Spring MVC

  • Complexity: Can be complex to set up and configure, especially for newcomers.
  • Configuration: Requires considerable configuration, though this is mitigated with Spring Boot.
  • Overhead: May introduce some overhead due to its comprehensive nature.

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