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Spring MVC Interview Questions and Answers

1
What is Spring MVC framework?

The Spring web MVC framework provides model-view-controller architecture and ready components that can be used to develop flexible and loosely coupled web applications. The MVC pattern results in separating the different aspects of the application (input logic, business logic, and UI logic), while providing a loose coupling between model, view and controller parts of application. Spring framework provides lots of advantages over other MVC frameworks e.g.

  • Clear separation of roles -- controller, validator, command object, form object, model object, DispatcherServlet, handler mapping, view resolver, etc. Each role can be fulfilled by a specialized object.
  • Powerful and straightforward configuration of both framework and application classes as JavaBeans.
  • Reusable business code -- no need for duplication. You can use existing business objects as command or form objects instead of mirroring them in order to extend a particular framework base class.
  • Customizable binding and validation
  • Customizable handler mapping and view resolution
  • Customizable locale and theme resolution
  • A JSP form tag library, introduced in Spring 2.0, that makes writing forms in JSP pages much easier. etc.
2
What is the front controller class of Spring MVC?

A front controller is defined as “a controller which handles all requests for a Web Application.” DispatcherServlet (actually a servlet) is the front controller in Spring MVC that intercepts every request and then dispatches/forwards requests to an appropriate controller.
When a web request is sent to a Spring MVC application, dispatcher servlet first receives the request. Then it organizes the different components configured in Spring’s web application context (e.g. actual request handler controller and view resolvers) or annotations present in the controller itself, all needed to handle the request.

3
How to use Tomcat JNDI DataSource in Spring Web Application?

For using servlet container configured JNDI DataSource, we need to configure it in the spring bean configuration file and then inject it to spring beans as dependencies. Then we can use it with JdbcTemplate to perform database operations.

< bean id="dataSource" class="org.springframework.jndi.JndiObjectFactoryBean">
< property name="jndiName" value="java:comp/env/jdbc/MySQLDB"/>
< /bean>

4
How to get ServletContext and ServletConfig object in a Spring Bean?

Simply implement ServletContextAware and ServletConfigAware interfaces and override below methods.
@Controller
@RequestMapping(value = "/magic")
public class SimpleController implements ServletContextAware, ServletConfigAware {

private ServletContext context;
private ServletConfig config;

@Override
public void setServletConfig(final ServletConfig servletConfig) {
this.config = servletConfig;

}

@Override
public void setServletContext(final ServletContext servletContext) {
this.context = servletContext;
}

//other code
}

5
How to achieve localization in Spring MVC applications?

Spring framework is shipped with LocaleResolver to support the internationalization and thus localization as well. To make Spring MVC application supports the internationalization, you will need to register two beans.

  • SessionLocaleResolver : It resolves locales by inspecting a predefined attribute in a user’s session. If the session attribute doesn’t exist, this locale resolver determines the default locale from the accept-language HTTP header.

    < bean id="localeResolver" class="org.springframework.web.servlet.i18n.SessionLocaleResolver">
    < property name="defaultLocale" value="en" />
    < /bean>

  • LocaleChangeInterceptor : This interceptor detects if a special parameter is present in the current HTTP request. The parameter name can be customized with the paramName property of this interceptor. If such a parameter is present in the current request, this interceptor changes the user’s locale according to the parameter value.

< bean id="localeChangeInterceptor" class="org.springframework.web.servlet.i18n.LocaleChangeInterceptor">
< property name="paramName" value="lang" />
< /bean>

< !-- Enable the interceptor -->
< bean class="org.springframework.web.servlet.mvc.annotation.DefaultAnnotationHandlerMapping">
< property name="interceptors">
< list>
< ref bean="localeChangeInterceptor" />
< /list>
< /property>
< /bean>
Next step is to have each locale specific properties file having texts in that locale specific language e.g.messages.properties and messages_zh_CN.properties etc.

6
What is Spring MVC Interceptor and how to use it?

As you know about servlet filters that they can pre-handle and post-handle every web request they serve — before and after it’s handled by that servlet. In the similar way, you can use HandlerInterceptor interface in your spring mvc application to pre-handle and post-handle web requests that are handled by Spring MVC controllers. These handlers are mostly used to manipulate the model attributes returned/submitted they are passed to the views/controllers.
A handler interceptor can be registered for particular URL mappings, so it only intercepts requests mapped to certain URLs. Each handler interceptor must implement the HandlerInterceptor interface, which contains three callback methods for you to implement: preHandle(), postHandle() and afterCompletion().
Problem with HandlerInterceptor interface is that your new class will have to implement all three methods irrespective of whether it is needed or not. To avoid overriding, you can use HandlerInterceptorAdapter class. This class implementsHandlerInterceptor and provide default blank implementations.

7
How does Spring MVC provide validation support?

Spring supports validations primarily into two ways.

    Using JSR-303 Annotations and any reference implementation e.g. Hibernate Validator
  • Using custom implementation of org.springframework.validation.Validator interface

In next question, you see an example about how to use validation support in spring MVC application

8
What is a MultipartResolver and when its used?

Spring comes with MultipartResolver to handle file upload in web application. There are two concrete implementations included in Spring:

  • CommonsMultipartResolver for Jakarta Commons FileUpload
  • StandardServletMultipartResolver for Servlet 3.0 Part API

To define an implementation, create a bean with the id “multipartResolver” in a DispatcherServlet’s application context. Such a resolver gets applied to all requests handled by that DispatcherServlet.
If a DispatcherServlet detects a multipart request, it will resolve it via the configured MultipartResolver and pass on a wrapped HttpServletRequest. Controllers can then cast their given request to the MultipartHttpServletRequest interface, which permits access to any MultipartFiles.

9
What does the ViewResolver class?

ViewResolver is an interface to be implemented by objects that can resolve views by name. There are plenty of ways using which you can resolve view names. These ways are supported by various in-built implementations of this interface. Most commonly used implementation is InternalResourceViewResolver class. It defines prefix and suffix properties to resolve the view component.

< bean class="org.springframework.web.servlet.view.InternalResourceViewResolver">
< property name="prefix" value="/WEB-INF/views/" />
< property name="suffix" value=".jsp" />
< /bean>
So with above view resolver configuration, if controller method return “login” string, then the “/WEB-INF/views/login.jsp” file will be searched and rendered.

10
What is the front controller class of Spring MVC?

The DispatcherServlet class works as the front controller in Spring MVC.

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