Overview

In the realm of Java web development, JSP (JavaServer Pages) frameworks like Apache Struts and Spring MVC play a crucial role. They help in building robust and scalable web applications by providing a structured model-view-controller (MVC) architecture. Understanding these frameworks is essential for developers looking to excel in JSP-based web application development.

Key Concepts

• MVC Architecture: Separates the application logic (Model), the user interface (View), and the control flow (Controller), facilitating easier maintenance and scalability.
• Form Handling and Validation: Both frameworks offer mechanisms for handling user inputs and validating them, crucial for developing secure web applications.
• Integration: How these frameworks integrate with other Java technologies (like JDBC, JPA for database access, and security frameworks) to create comprehensive web applications.

Common Interview Questions

Basic Level

1. What is the MVC pattern and how is it implemented in Apache Struts and Spring MVC?
2. How do you handle form data in Spring MVC?

Intermediate Level

3. Explain the role of Action classes in Struts.

Advanced Level

4. How does Spring MVC handle exception handling differently from Apache Struts?

Detailed Answers

1. What is the MVC pattern and how is it implemented in Apache Struts and Spring MVC?

Answer: The Model-View-Controller (MVC) pattern is a software design pattern that separates an application into three main logical components: Model, View, and Controller. This separation helps manage complexity in large applications, enabling easier maintenance and scalability.

• Apache Struts: Implements MVC where the ActionServlet acts as the Controller, directing requests to specific Action classes based on the configuration defined in struts-config.xml. The Model is represented by Action Forms and business logic classes, and the View is typically JSP pages using Struts tag libraries.
• Spring MVC: Utilizes DispatcherServlet as the Controller to route requests to appropriate handlers, defined as @Controller classes. Models are POJOs (Plain Old Java Objects) that are populated and manipulated within these controller classes and passed to the View, which is usually implemented using JSPs, Thymeleaf, or other view technologies.

Key Points:
- Both frameworks provide a clear separation of concerns.
- Struts uses XML for configuration, while Spring MVC favors annotations for most configurations.
- Spring MVC offers more flexibility in defining the Model component.

Example:

// This is a conceptual explanation; thus, a C# code example is not applicable.
// Please refer to Java-based examples for actual implementation details in Spring MVC or Apache Struts.

2. How do you handle form data in Spring MVC?

Answer: In Spring MVC, form data is commonly handled by defining a POJO (Plain Old Java Object) that corresponds to the form data structure. This POJO is then used as a command object in a controller method, annotated with @ModelAttribute.

Key Points:
- @RequestMapping is used to map the request URL to the controller method.
- @ModelAttribute binds form fields to the corresponding properties of the POJO.
- Spring's form tags in JSPs help in binding form fields directly to the properties of the POJO.

Example:

// C# is not used for Spring MVC code examples. Below is a conceptual placeholder.
// For actual code, refer to Java and Spring MVC annotations.

public class RegistrationForm {
    private String username;
    private String password;
    // Getters and setters
}

@RequestMapping(value = "/register", method = RequestMethod.POST)
public String submitRegistration(@ModelAttribute("registrationForm") RegistrationForm form, Model model) {
    // Handle registration logic using form data
    return "registrationSuccess";
}

3. Explain the role of Action classes in Struts.

Answer: In Apache Struts, Action classes serve as the "Controller" part of the MVC pattern. They are Java classes that extend the Action class and override the execute method. This method contains the business logic to process user requests and return a forward or redirect to a view.

Key Points:
- Action classes handle HTTP requests and responses.
- They interact with the Model to manipulate application data.
- The execute method returns an ActionForward object that defines the next view (JSP page) to display.

Example:

// C# is not used for Struts code examples. Below is a conceptual placeholder.
// For actual code, refer to Java and Struts framework.

public class LoginAction extends Action {
    public ActionForward execute(ActionMapping mapping, ActionForm form, HttpServletRequest request, HttpServletResponse response) {
        // Login logic
        return mapping.findForward("success");
    }
}

4. How does Spring MVC handle exception handling differently from Apache Struts?

Answer: Spring MVC provides a more flexible and comprehensive approach to exception handling compared to Apache Struts. In Spring MVC, exceptions can be handled globally using @ControllerAdvice classes or locally within individual controllers using @ExceptionHandler methods. This approach allows for centralized exception handling strategies, reducing boilerplate code and improving maintainability.

Key Points:
- @ExceptionHandler can be used for specific exceptions within a controller.
- @ControllerAdvice allows for global exception handling across all controllers.
- Struts relies on declarative exception handling in the struts-config.xml file, mapping exceptions to global forwards.

Example:

// C# is not used for Spring MVC code examples. Below is a conceptual placeholder.
// For actual code, refer to Java and Spring MVC annotations.

@ControllerAdvice
public class GlobalExceptionHandler {
    @ExceptionHandler(value = Exception.class)
    public ModelAndView defaultErrorHandler(HttpServletRequest req, Exception e) {
        // Handle exceptions
    }
}