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Struts 2 Interview Questions and Answers

This section covers frequently asked Struts 2 interview questions.

1. What is Struts?

Struts is a popular open-source framework for developing Java web applications using the Model-View-Controller (MVC) design pattern. Struts 2 is based on the WebWork framework.

2. Struts 1 vs. Struts 2.

Feature Struts 1 Struts 2
Action Class Must extend an abstract class Plain Old Java Object (POJO)
Front Controller ActionServlet StrutsPrepareAndExecuteFilter
Request Processing RequestProcessor Interceptors
View Technology Primarily JSP JSP, FreeMarker, Velocity
Configuration File [anyname].xml in WEB-INF struts.xml in the classpath

3. Features of Struts 2.

  • MVC architecture
  • POJO-based actions
  • AJAX support
  • Rich tag library
  • Various result types
  • Integration with other frameworks

4. What is MVC? (Repeated from earlier section).

MVC (Model-View-Controller) is a design pattern separating application logic into three parts: Model (data), View (presentation), and Controller (handling user input).

5. What is an Interceptor?

An interceptor is a pluggable component invoked before and/or after a request is processed. It's used for cross-cutting concerns (like logging, security, etc.).

6. Interceptor Lifecycle Methods.

  • init()
  • intercept(ActionInvocation invocation)
  • destroy()

7. ValueStack.

The ValueStack is a data structure holding the action and other model objects.

8. ActionContext.

ActionContext is a container for request-specific data.

9. ActionInvocation.

ActionInvocation invokes the action and manages interceptors.

10. OGNL (Object-Graph Navigation Language).

OGNL is Struts 2's expression language for accessing and manipulating objects.

11. Constants of the Action Interface.

  • SUCCESS
  • ERROR
  • INPUT
  • LOGIN
  • NONE

12. params Interceptor.

The params interceptor pushes request parameters onto the ValueStack.

13. execAndWait Interceptor.

execAndWait handles asynchronous operations and waits for the result.

14. modelDriven Interceptor.

modelDriven makes a model object the default object on the ValueStack.

15. validation Interceptor.

validation performs input validation.

16. Bundled Validators.

(This section lists built-in Struts 2 validators.)

17. Plain Validator vs. Field Validator.

A plain validator can be applied to multiple fields. A field validator applies to a specific field.

18. jsonValidation Interceptor.

jsonValidation supports asynchronous validation using JSON.

19. Aware Interfaces.

Aware interfaces (ServletRequestAware, ServletResponseAware, SessionAware, ServletContextAware) provide access to servlet-related objects.

20. i18n Interceptor.

The i18n interceptor handles internationalization (localization).