Spring 3 MVC – Introduction to Spring 3 MVC Framework

In Spring Web MVC you can use any object as a command or form-backing object; you do not need to implement a framework-specific interface or base class. Spring’s data binding is highly flexible: for example, it treats type mismatches as validation errors that can be evaluated by the application, not as system errors. Thus you need not duplicate your business objects’ properties as simple, untyped strings in your form objects simply to handle invalid submissions, or to convert the Strings properly. Instead, it is often preferable to bind directly to your business objects.

Request Processing Lifecycle



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

is completely integrated with Spring IoC container and allows us to use every other feature of Spring.

Following is the Request process lifecycle of Spring 3.0 MVC:

The client sends a request to web container in the form of http request.

This incoming request is intercepted by Front controller (

DispatcherServlet

) and it will then tries to find out appropriate Handler Mappings.

With the help of Handler Mappings, the

DispatcherServlet

will dispatch the request to appropriate Controller.

The Controller tries to process the request and returns the Model and View object in form of

ModelAndView

instance to the Front Controller.

The Front Controller then tries to resolve the View (which can be JSP, Freemarker, Velocity etc) by consulting the View Resolver object.

The selected view is then rendered back to client.

Features of Spring 3.0

Spring 3.0 framework supports Java 5. It provides annotation based configuration support. Java 5 features such as generics, annotations, varargs etc can be used in Spring.

A new expression language Spring Expression Language SpEL is being introduced. The Spring Expression Language can be used while defining the XML and Annotation based bean definition.

Spring 3.0 framework supports REST web services.

Data formatting can never be so easy. Spring 3.0 supports annotation based formatting. We can now use the

@DateFimeFormat(iso=ISO.DATE)

and

@NumberFormat(style=Style.CURRENCY)

annotations to convert the date and currency formats.

Spring 3.0 has started support to JPA 2.0.

Configuring Spring 3.0 MVC

The entry point of Spring 3.0 MVC is the

DispatcherServlet

.

DispatcherServlet

is a normal servlet class which implements

HttpServlet

base class. Thus we need to configure it in

web.xml

.

<web-app>

<servlet>
<servlet-name>example</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>

<servlet-mapping>
<servlet-name>example</servlet-name>
<url-pattern>*.html</url-pattern>
</servlet-mapping>
</web-app>

In above code snippet, we have configure

DispatcherServlet

in

web.xml

. Note that we have mapped

*.html

url pattern with example

DispatcherServlet

. Thus any url with

*.html

pattern will call Spring MVC Front controller.



Once the

DispatcherServlet

is initialized, it will looks for a file names

[servlet-name]-servlet.xml

in

WEB-INF

folder of web application. In above example, the framework will look for file called

example-servlet.xml

.

Note the above architecture diagram. The

WebApplicationContext

specified in above diagram is an extension of the plain

ApplicationContext

with some extra feature necessary for web applications. The

WebApplicationContext

is capable of resolving themes and it is also associated with corresponding servlet. The

WebApplicationContext

is bound in the

ServletContext

, and by using static methods on the

RequestContextUtils

class you can always look up the

WebApplicationContext

.