When preparing for Java interviews, it's crucial to focus on Core Java questions. However, preparing for advanced Java questions is equally important. Advanced Java plays a significant role in web application development, so understanding it is very important and essential. In this article, I will share some of the most frequently asked advanced Java interview questions and their answers.
30 Advanced Java Interview Questions & Answers:
1. What’s the difference between GET and POST?
GET sends request parameters in the URL, while POST sends them in the message body. GET is used for retrieving data, while POST is used for sending data to be processed.
2. What is a Session?
A session is a single visit to a website. It starts when a user arrives and ends when they leave or close their browser. The server tracks this session using a unique ID, which can be stored in a cookie or URL.
3. What is a Servlet?
A servlet is a small Java program that runs on a web server. It handles requests from web clients (like browsers) and responds to them, usually over HTTP.
4. How do you handle concurrency in Servlets?
Servlets handle concurrency by creating a new thread for each request. Synchronization is managed internally by the servlet container.
5. What are Filters in Servlets?
Filters are objects that perform filtering tasks on either the request to a resource, the response from a resource, or both. They can be used for tasks like logging, authentication, and data transformation.
6. What is the ServletContext?
ServletContext is an interface used to interact with the servlet container. It provides methods to access application-wide parameters and resources.
7. What is JSP?
JavaServer Pages (JSP) is a technology for creating dynamic web pages quickly. JSP pages are text files that mix HTML with Java code to generate web content.
8. What is the difference between Servlet and JSP?
Servlets are Java programs that handle server-side logic and HTTP requests. JSP is a technology for embedding Java code in HTML to create dynamic web pages. Servlets handle business logic, while JSP focuses on presentation.
9. Explain the lifecycle of a Servlet.
A servlet goes through three main stages: initialization (init()), request handling (service()), and destruction (destroy()). init() sets up the servlet, service() processes requests, and destroy() cleans up resources.
10. What is the purpose of the web.xml file in a Servlet application?
The web.xml file is the configuration file for a Servlet application. It specifies settings like servlet mappings, initialization parameters, and error pages.
11. Differentiate between forward and sendRedirect in Servlets.
forward is server-side and keeps the URL the same while passing the request to another resource. sendRedirect is client-side and changes the URL by sending a new request to the redirected resource.
12. Explain the MVC (Model-View-Controller) architecture and how it is implemented in Servlets.
MVC is a design pattern that separates an application into three parts: Model (data), View (UI), and Controller (logic). In Servlets, the controller handles requests, the model manages data, and the view displays the result.
13. What is a JSP Tag Library?
A JSP tag library provides custom tags that can be used in JSP pages. These tags simplify complex tasks and make JSP pages easier to read and maintain.
14. How does session tracking work in Servlets?
Session tracking in Servlets uses methods like cookies, URL rewriting, and HttpSession. HttpSession helps store user data between multiple requests.
15. Explain the purpose of the init() and destroy() methods in a JSP page.
The init() method runs when a JSP page is first loaded, and destroy() runs when the page is unloaded. They are used for setting up and cleaning up resources.
16. What are Cookies?
Cookies are small pieces of data sent by a server to a user’s browser. They store information like user preferences and login details so that the next time the user visits the site, the server can recognize them.
17. What is the purpose of the HttpServletRequest and HttpServletResponse objects?
HttpServletRequest handles client requests and provides methods to retrieve request data. HttpServletResponse is used to construct and send the response back to the client.
18. What are JavaBeans and how are they used in JSP?
JavaBeans are reusable Java components that follow specific conventions (like having a no-argument constructor and getter/setter methods). They are used in JSP for encapsulating data and logic.
19. Explain the use of the @WebServlet annotation.
The @WebServlet annotation is used to declare a servlet and map it to a URL pattern without needing to use the web.xml file.
20. What is the role of RequestDispatcher?
RequestDispatcher allows forwarding a request from one servlet to another resource (like another servlet, JSP, or HTML file) or including the response from another resource in the current response.
21. What is a Servlet Filter Chain?
A Servlet Filter Chain is a series of filters applied in sequence to requests and responses. Each filter can perform operations before and after the request reaches the target resource.
22. How do you handle file uploads in Servlets?
File uploads in Servlets are handled using libraries like Apache Commons FileUpload or Servlet 3.0's @MultipartConfig annotation.
23. What is the difference between the include directive (<%@ include %>) and action (<jsp:include>) in JSP?
The include directive adds the content of another file at page translation time, while the include action adds content at request time. The directive is part of the page before it is compiled, and the action is processed during runtime.
24. How does exception handling work in JSP?
JSP handles exceptions using the errorPage attribute in the page directive. When an error occurs, the request is forwarded to the specified error page for display.
25. What are @Controller and @RestController in Spring MVC?
@Controller is used to define a controller in Spring MVC, which handles web requests and returns views. @RestController is a specialized version that combines @Controller and @ResponseBody, returning data directly as JSON or XML.
26. Explain the purpose of the @RequestMapping annotation.
@RequestMapping maps web requests to specific handler methods in a controller. It defines the URL pattern, request method (GET, POST), and other parameters.
27. What is Spring Boot and how does it simplify application development?
Spring Boot is a framework that simplifies the setup and development of Spring applications by providing default configurations and built-in features, allowing developers to focus on writing code.
28. What are Spring Boot starters?
Spring Boot starters are predefined sets of dependencies that simplify the inclusion of common functionality in a Spring Boot application, like web development or data access.
29. How does Spring Boot handle dependency injection?
Spring Boot uses Spring’s dependency injection mechanism to manage application components and their dependencies. It automatically wires beans based on annotations and configuration.
30. What is the difference between @Component, @Service, and @Repository annotations in Spring?
@Component is a generic stereotype for any Spring-managed component. @Service is used for service layer components, and @Repository is used for data access components, with added persistence-specific functionality.
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