Servlet Interview Questions and Answers for 5 years experience

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Servlet Interview Questions and Answers (5 Years Experience)

  1. What is a Servlet?

    • Answer: A Servlet is a Java class that extends the capabilities of servers that host applications accessed by means of a request-response programming model. It's a server-side component that runs inside a servlet container (like Tomcat or Jetty) and handles client requests, processes data, and generates dynamic web content.

  2. Explain the Servlet lifecycle.

    • Answer: The servlet lifecycle consists of several phases: loading and instantiation, initialization (init()), request handling (service()), and destruction (destroy()). The container loads and instantiates the servlet, calls the init() method once to initialize it, then handles multiple requests by calling the service() method (which in turn calls doGet(), doPost(), etc., depending on the request type). Finally, the destroy() method is called before the servlet is unloaded.

  3. What is the difference between doGet() and doPost() methods?

    • Answer: doGet() handles HTTP GET requests, typically used for retrieving data. doPost() handles HTTP POST requests, typically used for submitting data. GET requests append data to the URL, while POST requests send data in the request body, making POST more secure for sensitive data.

  4. What is a ServletContext?

    • Answer: ServletContext provides a way for servlets to communicate with each other and access server-wide information, such as initialization parameters, context path, and resources. It's a single instance per web application.

  5. What is a ServletConfig?

    • Answer: ServletConfig provides information about the servlet itself, including initialization parameters defined in the deployment descriptor (web.xml) or annotations. It's specific to each servlet instance.

  6. Explain the use of HttpSession.

    • Answer: HttpSession provides a way to maintain state across multiple requests from the same client. It allows you to store attributes associated with a specific user session, enabling features like shopping carts, user logins, and personalized content.

  7. How do you handle exceptions in servlets?

    • Answer: You can use try-catch blocks within servlet methods to handle exceptions. For unhandled exceptions, you can configure a servlet container's error page handling to display a custom error message or redirect to an error page.

  8. What are Servlet filters?

    • Answer: Servlet filters are components that intercept requests and responses, allowing you to perform pre-processing (e.g., authentication, logging) or post-processing (e.g., compression, data transformation) before the request reaches the servlet or after the servlet generates a response.

  9. What are Servlet listeners?

    • Answer: Servlet listeners are components that respond to events in the servlet lifecycle or the web application lifecycle (e.g., context initialization, session creation, session destruction). They are used for tasks like resource initialization, cleanup, and monitoring.

  10. Explain the difference between forward() and sendRedirect().

    • Answer: `forward()` is a server-side redirect; it happens within the container, and the client's browser remains unaware of the redirection. `sendRedirect()` is a client-side redirect; the client's browser receives a new HTTP response with the redirect instruction, causing a new request to the new URL.

  11. How to handle file uploads in Servlets?

    • Answer: File uploads are typically handled using the `MultipartHttpServletRequest` interface (often through libraries like Apache Commons FileUpload). This interface provides methods to access the uploaded file parts, including the file content, filename, and content type. You'll need to handle the parsing of multipart data and store the file on the server.

  12. What are the different scopes in JSP?

    • Answer: JSP scopes determine the visibility and lifespan of objects. They include page, request, session, and application scope. Page scope is limited to a single JSP page, request scope lasts for a single HTTP request, session scope for a user session, and application scope for the entire web application.

  13. Explain how to use JDBC with Servlets.

    • Answer: JDBC is used to connect to a database from a Servlet. You load the JDBC driver, establish a connection using a connection URL, credentials, and create a statement object to execute SQL queries. Results are fetched and processed, and the connection is closed after use. Be sure to handle exceptions appropriately and use connection pooling for performance.

  14. What is a web.xml file and its purpose?

    • Answer: web.xml is the deployment descriptor file for a web application. It defines configurations such as servlet mappings, filter configurations, listener configurations, security constraints, and other settings needed by the web application.

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