2.2. Overview of Spring MVC Architecture

Official website of Spring MVC says the following

Spring Reference Document.

Spring’s web MVC framework is, like many other web MVC frameworks, request-driven, designed around a central Servlet that dispatches requests to controllers and offers other functionality that facilitates the development of web applications. Spring’s DispatcherServlet however, does more than just that. It is completely integrated with the Spring IoC container and as such allows you to use every other feature that Spring has.

2.2.1. Overview of Spring MVC Processing Sequence

The processing flow of Spring MVC from receiving the request till the response is returned is shown in the following diagram.

1. DispatcherServlet receives the request.
2. DispatcherServlet dispatches the task of selecting an appropriate controller to HandlerMapping. HandlerMapping selects the controller which is mapped to the incoming request URL and returns the (selected Handler) and Controller to DispatcherServlet.
3. DispatcherServlet dispatches the task of executing of business logic of Controller to HandlerAdapter.
4. HandlerAdapter calls the business logic process of Controller.
5. Controller executes the business logic, sets the processing result in Model and returns the logical name of view to HandlerAdapter.
6. DispatcherServlet dispatches the task of resolving the View corresponding to the View name to ViewResolver. ViewResolver returns the View mapped to View name.
7. DispatcherServlet dispatches the rendering process to returned View.
8. View renders Model data and returns the response.

2.2.2. Implementation of each component

Among the components explained previously, the extendable components are implemented.

2.2.2.1. Implementation of HandlerMapping

Class hierarchy of HandlerMapping provided by Spring framework is shown below.

Usually org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerMapping is used. This class reads @RequestMapping annotation from the Controller and uses the method of Controller that matches with URL as Handler class.

In Spring3.1, RequestMappingHandlerMapping is enabled by default when <mvc:annotation-driven> is set in Bean definition file read by DispatcherServlet. (For the settings which get enabled with the use of <mvc:annotation-driven> annotation, refer Web MVC framework.)

2.2.2.2. Implementation of HandlerAdapter

Class hierarchy of HandlerAdapter provided by Spring framework is shown below.

Usually org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter is used. RequestMappingHandlerAdapter class calls the method of handler class (Controller) selected by HandlerMapping. In Spring 3.1, this class is also configured by default throught <mvc:annotation-driven>.

2.2.2.3. Implementation of ViewResolver

Classes that implement ViewResolver provided by Spring framework and dependent libraries are shown below.

Normally (When JSP is used),

• org.springframework.web.servlet.view.InternalResourceViewResolver is used,

however, when template engine Tiles is to be used

• org.springframework.web.servlet.view.tiles2.TilesViewResolver

and when stream is to be returned for file download

• org.springframework.web.servlet.view.BeanNameViewResolver

Thereby, it is required to use different viewResolver based on the type of the View that needs to be returned.

When View of multiple types is to be handled, multiple definitions of ViewResolver are required.

A typical example of using multiple ViewResolver is the screen application for which file download process exists.

For screen (JSP), View is resolved using InternalResourceViewResolver and for File download View is resolved using BeanNameViewResolver.

For details, refer [coming soon] File Download.

2.2.2.4. Implementation of View

Classes that implement View provided by Spring framework and its dependent libraries are shown below.

View changes with the type of response to be returned. When JSP is to be returned, org.springframework.web.servlet.view.JstlView is used. When View not provided by Spring framework and its dependent libraries are to be handled, it is necessary to extend the class in which View interface is implemented. For details, refer [coming soon] File Download.