Spring has become one of the most used Java frameworks for the development of web-applications. All the new Java applications are by default using Spring core and Spring MVC frameworks. Thanks to its growing popularity, recruiters all over the globe are looking for candidates hands-on with the Spring framework. If you’re appearing for an interview for a Java developer role, Spring MVC is one of the first things that you should brush up – irrespective of whether you’re a fresher or someone with experience.
In this article, we’ll be talking about 15 such Spring MVC must-know questions which you can expect to encounter in any interview you sit for.
1. What is the Spring framework?
Spring is an open-source framework that was built to simplify application development. It has a layered structure which allows the developer to be selective about the components they use. It has three main components – Spring Core, Spring AOP, and Spring MVC.
Further, you can talk about your experience with Spring, if any. That’ll add a lot of weight to your answer.
2. What are the main features of Spring framework?
Spring framework offers a lot of features to make the developer’s life easy. Some of them are:
- Lightweight: Spring is extremely lightweight, the basic version is around 1MB, with negligible processing overheads.
- Inversion of Control (IoC): Dependency Injection or Inversion of Control is one of the most important features of Spring. Using IoC, the developers don’t need to create the complete environment for the object and its dependencies; they can simply create and test the object they are handling at the given point of time. Object dependencies will be included or called upon when the need arises.
- Aspect Oriented Programming: Spring supports Aspect Oriented Programming. AOP isolates secondary functions from the programmer’s business logic. This not only provides modularity but also makes the code maintainable.
- MVC architecture: Spring comes with an MVC framework for web-applications. This framework is highly configurable using various technologies like JSP, Tiles, iText, and POI.
- JDBC exception handling: Spring comes with a predefined JDBC abstraction layer which simplifies the overall exception handling process.
3. Explain a bit more about Dependency Injection.
Inversion of Control or Dependency Injection aims to simplify the process of object creation by following a simple concept – don’t create objects, just describe how they should be created. Using IoC, the objects are given their dependencies at build-time by an external entity that is responsible for coordinating each object in the system. In essence, we’re injecting dependencies into objects using IOC or Dependency Injection.
4. Explain the different types of Dependency Injections in Spring? When to use which?
Spring provides the developers with the following two types of dependency injections:
- Constructor-based DI: Constructor-based DI is accomplished by passing a number of arguments (each of which represents a dependency on other class) to a class’s constructor. Simply, dependencies are given in the form of constructor parameters.
- Setter-based DI: When you are working with a no-argument constructor, you will set values by passing arguments through setter function to instantiate the bean under consideration, this is called setter-based dependency injection.
5. What is the Spring MVC framework?
Spring MVC is one of the core components of the Spring framework. It comes with ready to use components and elements that help developers build flexible and robust web applications. As the name suggests, the MVC architecture separates the different aspects of the application – input logic, business logic, and UI logic. It also provides a loose coupling between the M, V, and C of the application.
6. What are some benefits of Spring MVC framework over other MVC frameworks?
The Spring MVC framework has some clear benefits over other frameworks. Some of the benefits are:
- Clear separation of roles – There is a specialised object for every role, thus providing a clear separation of roles.
- Reusable business code – With Spring MVC, you don’t need to duplicate your code. You can use your existing objects as commands instead of mirroring them in order to extend a particular framework base class.
- Customizable binding and validation
- Customizable locale and theme resolution
- Customizable handler mapping and view resolution
- From Spring 2.0 onwards, the framework comes with a JSP form tag library which makes writing forms in JSP pages much easier.
7. What is DispatcherServlet?
Spring MVC framework is request-driven and is designed around a central Servlet that handles all the HTTP requests and responses. The DispatcherServlet, however, does a lot more than just that. It seamlessly integrates with the IoC container and allows you to use each feature of Spring.
On receiving an HTTP request, the DispatcherServlet consults HandlerMapping (these are the configuration files) to call the appropriate Controller. Then, the controller calls appropriate service methods to set the Model data. It also returns the view name to DispatcherServlet. DispatcherServlet, with the help of ViewResolver, picks up the defined view for the request. Once the view is finalised, the DispatcherServlet passes the Model data to View – where it is finally rendered on the browser.
8. What is the front controller class of the Spring MVC?
A front controller is a controller which handles all requests for a Web application. When it comes to Spring MVC, DispatcherServlet is that front controller. When a web request is sent to a Spring MVC application, the DIspatcherServlet takes care of everything. First, it takes the request. Then, it organises the different components like request handlers, controllers, view resolvers, and such – all needed to handle the request. And finally, it renders the content on the browser.
9. What is a Viewresolver pattern and how does it work in MVC?
View Resolver is a J2EE pattern which allows the applications to dynamically choose a technology for rendering the data on the browser (View). Any technology like HTML, JSP, Tapestry, XSLT, JSF, or any other such technology can be used for View. The View Resolver pattern holds the mapping of different views. The Controller returns the name of the View which is then passed to View Resolver for selecting the appropriate technology.
10. How does Spring MVC provide validation support?
Spring primarily supports two types of validations:
- Using JSR-303 Annotations and any reference implementation, for example, Hibernate Validator, or
- Implementing org.springframework.validation.Validator interface.
11. A user gets a validation error in other fields on checking a checkbox, after which, he unchecks it. What would be the current selection status in command object of the Spring MVC? How will you fix this issue?
This is one of the trickier questions to answer if you aren’t aware of the HTTP Post behaviour in Spring MVC.
During HTTP Post, if you uncheck the checkbox, then HTTP does not include a request parameter for the checkbox – which means the updated selection won’t be picked up. To fix that, you can use hidden form field which starts with ‘_’.
12. How will you compare the MVC framework to the three-tier architecture?
A Three-tier architecture is an architecture style whereas MVC is a design pattern.
Having said that, in larger applications, MVC forms the presentation tier of a three-tier architecture. The Model, View, and Controller are concerned only with the presentation – they use the middle tier to populate their models.
13. How should we use JDBC in Spring to optimise the performance?
Spring provides a template class called as JDBCTemplate. Using JDBC with this template gives manifolds better performance.
14. What do you mean by a “Bean” in the context of Spring framework?
Any class that is initialised by the IoC container is known as a bean in Spring. The lifecycle of a Spring Bean is managed by Spring IoC Container.
15. What is a “Scope” in reference to Spring Beans?
Spring Beans comes with following five scopes:
- Prototype: Whenever there’s a request for a bean, a separate prototype is created each time.
- Request: It is like the previous scope, but only for web-based applications. For each HTTP request, Spring creates a new bean instance.
- Singleton: There’s only one bean created for every container, and it acts as the default scope of that bean. In all these instances, the beans cannot use a shared instance variable as it can lead to data-inconsistency.
- Session: A bean is created for every HTTP session.
- Global-session: Global session is created for Portlet applications.
The Spring framework is extendable, that is, you can create your own scope as well. The “scope” attribute of the bean element is used to define the scope.
This was all about the must-know questions and answers revolving around the Spring framework – and Spring MVC, to be precise. If you’re a Java developer looking to get started with Spring, there couldn’t be a better time! Organisations are on a look-out for developers having strong command on this framework – thanks to the features it has to offer.
If you had any doubt in any of the questions above, do let us know in the comments below! All the best with that Spring MVC interview!