Spring MVC Architecture

thirdparty image

Execution flow:-

• Client sends an HTTP request to a specific URL
• DispatcherServlet of Spring MVC receives the request
• It passes the request to a specific controller depending on the URL requested using @Controller and @RequestMapping annotations.
• Spring MVC Controller then returns a logical view name and model to DispatcherServlet.
• DispatcherServlet consults view resolvers until actual View is determined to render the output
• DispatcherServlet contacts the chosen view (e.g. Freemarker, JSP) with model data and it renders the output depending on the model data
• The rendered output is returned to the client as response

ü  You should Configure DispatcherServlet in web.xml as following..

<servlet>     

 <servlet-name>spring</servlet-name>  

    <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>  

    <load-on-startup>1</load-on-startup>  

</servlet>  

<servlet-mapping>  

    <servlet-name>spring</servlet-name>  

    <url-pattern>*.html</url-pattern>  

</servlet-mapping>

ü  At web container startup.

·         DispatcherServlet will be loaded , Instantiated and initialized by calling init() method.

·         Init() method of DispatcherServlet will try to identify the Spring Configuration Document with following naming conversions.

Servlet_name-servlet.xml

Ex:

Dashzin-servlet.xml

ü  DispatcherServlet create the ApplicationContext (XmlWebApplicationContext) object by reading all the beans specified in the Spring Configuration Document.

ü  If Spring Configuration Document is not found with the given naming conversion then ApplicationContext object will not be created by the DispatcherServlet.

Example:-

Public class DispatcherServlet extends HttpServlet{

ApplicationContext ctx=null;

Public void init(ServletConfig cfg){

// try  to get the spring Configuration Documents with the default naming conversions

String xml=”Dashzin”+”-servlet.xml”;

// if found then create the ApplicationContext object

Ctx=new XmlWebApplicationContext(xml);

}

……

}

After Deploying and starting SpringMVC based web application , following tasks will happen at web Container start-up.

ü  Web Container loads, create and initialize DispatcherServlet by calling init() method.

ü  DispatcherServlet’s init() performs the following:-

·         Identifies spring configuration document file

·         Spring Container instance will be created by reading all the beans from identified spring configuration document  

·         Initializes the DispatcherServlet with spring container instances

Following task will happen at Web Container shutdown-time

ü  Web container call destroy() method of DispatcherServlet.

ü  destroy() method of DispatcherServlet destroys the spring container instance.