Top 20+ Servlet Interview Questions & Answers [ J2EE TRICKS ]

Last updated on 04th Jul 2020, Blog, Interview Questions

An extension of a server’s functionality is possible with servlets, a Java-based technology. Developers can generate content dynamically in response to user requests by using servlets, which are widely used to create dynamic web applications. With the ability to generate dynamic content and respond to requests from web clients (browsers), servlets are Java classes that increase the functionality of servers that host applications.

1. Explain a Servlet.

Ans:

An essential part of Java web applications running on servers is a Servlet. It’s basically a Java class that, in response to client requests, dynamically generates content to expand the capabilities of a web server. Servlets run on web servers or application servers that support Java, like Apache Tomcat or Jetty.

2. How is a Servlet started?

Ans:

The `<init-param>` element in the servlet declaration within the web.xml file can be used to initialise servlets. This element allows developers to specify servlet initialization settings, allowing them to customise the servlet’s behaviour during its initialization phase. These parameters are then available to developers via the servlet’s init() method, allowing them to conduct one-time setup activities or customise the servlet based on the supplied parameters.

3. What does a Servlet’s init() function do?

Ans:

Throughout a servlet’s life cycle, the init() method is essential. When the servlet is being placed into service, it is automatically called by the servlet container during the initialization step. This function is called just once, usually upon initial servlet loading or web application startup. The main function of the init() method is to carry out any one-time initialization work that needs to be done by the servlet before it can process requests from clients.

4. What distinguishes a Servlet from an Applet?

Ans:

Although they both use Java, Servlets and Applets have different uses and operate in different settings.

• As server-side components, servlets run on the web server in response to requests from clients. They manage sessions, create dynamic web pages, and communicate with databases in order to execute requests.
• In contrast, Applets are client-side programmes that operate on the user’s computer within a web browser. Usually integrated into HTML sites, their purpose is to improve the user interface by offering graphical and interactive content.

5. What does the function service() do?

Ans:

A crucial part of the servlet life cycle that manages client requests is the `service()` method in servlets. The servlet container invokes the `service()` method in response to each request a client sends to the servlet in order to handle that specific request. Every time a request comes in, this function is called, enabling the servlet to dynamically produce the proper result.

Java Code:

public void service(ServletRequest req, ServletResponse res) throws ServletException,

6. Describe the doPost() and doGet() functions.

Ans:

The Java HttpServlet class’s doGet() and doPost() methods are particular implementations of the more general service() method. These methods are essential for handling various client request types because they are made to handle HTTP GET and POST requests, respectively.

An illustration of the doGet() function:

protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException.

An illustration of the doPost() function:

protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException.

7. What does the destroy() method accomplish?

Ans:

The servlet container calls the `destroy()` method, which is a component of the servlet life cycle, prior to removing a servlet instance. Using this method gives the servlet the chance to tidy up, release resources, and end any running processes with grace. When it comes to handling resources that were initialised during the servlet life cycle’s `init() `phase, the `destroy()` method is especially helpful.

8. Explain the getInitParameter() method’s purpose.

Ans:

• ‘getInitParameter()’ The purpose of this method is to retrieve the value of an initialization parameter supplied in the servlet’s deployment descriptor (‘web.xml’).
• Takes a parameter name as an argument and returns its preset value.
• During the initialization phase, servlets can access configuration information defined in the deployment descriptor.
• Allows for servlet customization and adaptability based on external configuration.

9. Distinguish between RequestDispatcher.forward() and RequestDispatcher.include().

Ans:

• RequestDispatcher.forward(): This function is used for server-side redirection. The original request and response objects are passed on to a different resource. The client is unaware of the forward because control has been passed to the new resource.
• RequestDispatcher.include(): In terms of performance, efficient.Include the content of another resource in the response using The original as well as the included resource both contribute to the final response. After inclusion, control returns to the original resource.

10. What is the function of the ServletContext object?

Ans:

The ‘ServletContext’ object acts as a vital interface between a servlet and its environment, representing the complete web application. Its key functions include allowing communication among servlets within the same application, sharing resources, and accessing configuration information. The `ServletContext’ is useful in circumstances where servlets must exchange data by providing a shared environment for information transfer.

11. Describe the distinctions between HttpSession and URL rewriting for session.

Ans:

	URL Rewriting	HTTPSession
Mechanism	Appending session-related data, usually in the form of a session identifier, to URLs created by web applications is the mechanism for URL rewriting.	In contrast, session data is stored on the server side using HttpSession. A distinct session object is allocated to each client.
Data Storage	By including the session data as parameters in the URL, the server is able to recognise and match requests to the relevant session.	Rather than being included in every URL, the session data is stored on the server, and just a session identifier—typically in the form of a cookie.
Visibility	Users may see and manage the session information in the browser’s address bar since it is a component of the URL.	The session identification is not visible to users and does not clog the URL because it is usually kept as a cookie.
Security	Since URL rewriting exposes critical information and makes it susceptible to manipulation, security risks may arise.	HttpSession is usually thought to be more secure than URL rewriting.

12. How can a Servlet read form data?

Ans:

The `getParameter()` function of the `HttpServletRequest` object is used to read form data in a Servlet. This method enables the servlet to extract the form parameters that are provided in the request when a client submits a form. The servlet obtains the associated value by passing the name of the form field as an input to `getParameter()`. For example, if a form has a field called “username,” the servlet can utilise a request to get the value of that field.”username” is the getParameter. 

13. What Is A Servlet Filter?

Ans:

A Java class called Servlet Filter is intended to intercept and handle requests and responses in a web application. Before or after the request reaches the servlet, or before the response is returned to the client, filters are set up to carry out particular actions. These duties may involve request/response header modification, input validation, authentication, logging, and encryption.

14. Describe the intent of the sendRedirect() function.

Ans:

A Servlet’s sendRedirect() method is used to tell the client’s browser to go to an alternate URL. By sending the new URL and a temporary redirect answer (HTTP status code 302), this technique forces the browser to perform a new request to the new address. This is especially helpful in situations when you need to handle form submissions, since you can utilise redirections to show users a confirmation page or point them to another area of the application.

15. What distinguishes HttpServletRequest from HttpServletResponse?

Ans:

• Aspect HttpServletRequestGoal of HttpServletResponserepresents the request to the servlet from the client.represents the response that will be returned to the client from the servlet.
• Application Used to get details about the incoming request, including headers, arguments, and session information.used to write the content, set cookies, set headers, and assemble and send the response to the client.
• Techniques Provides functions like getParameter(), getHeader(), and getSession() for accessing request-related data.provides functions like setStatus(), setHeader(), and getWriter() for configuring response attributes.

16. What does a Servlets session mean?

Ans:

A session in Servlets is a way to keep stateful communication going between a web server and a particular client over the course of several requests. By doing so, the user can interact with the application and travel across different pages while the information remains persistent on the server. User-specific information, such login credentials, preferences, or the contents of a shopping cart, is crucially stored in sessions.

17. What is collaboration with Servlets and how is it accomplished?

Ans:

In order to complete a task or provide a coherent answer to a client request, several servlets must coordinate and communicate with one another.

• Request Dispatching: Servlets can use the RequestDispatcher interface to send a request to another servlet.
• Forward Mechanism: A servlet can transfer control to another servlet through the use of the forward mechanism.
• Include Mechanism: One servlet can incorporate material created by another servlet into its own response by using the include() function, which is supported by the RequestDispatcher interface.

18. In a Servlet, how can a cookie be created?

Ans:

Using the Cookie class in a Servlet and adding it to the response is how a cookie is created. The javax.servlet.http package contains the Cookie class, which gives programmers the ability to specify key-value pairs that correspond to the data they wish to save on the client’s computer.

This is a quick synopsis of the procedure:

Create an object called a cookie:

Configure optional properties (if needed):

Add the Cookie to the response:

19. What is the process for managing exceptions in Servlets?

Ans:

Servlets use the standard `try-catch` mechanism that comes with the Java programming language to handle exceptions. Servlet programmers use try blocks to isolate code that can potentially throw exceptions, and then they provide catch blocks to handle such exceptions gracefully. By using this method, servlets may handle errors and react correctly, avoiding unplanned crashes.

20. What does the web.xml file’s error-page element serve as?

Ans:

Custom error pages for particular HTTP error codes within a web application can be configured using the error-page element in the web.xml file. Developers can improve the user experience by correlating error codes with aesthetically pleasant and informative error pages. This way, when mistakes occur, users can receive more visually appealing and useful notifications.

21. How can a Servlet session be invalidated?

Ans:

The HttpSession object invalidate() method can be used in Servlets to invalidate a session. When this function is used, the session is effectively ended, and all client-related session data is deleted. This function is usually used by servlet developers to log out users, reset session variables, or end a user’s session with the web application.

22. Describe how to utilise the AsyncContext API.

Ans:

• Suspension of Request Processing: The `AsyncContext` interface permits the suspension of a request’s processing.
• Asynchronous Operations: The `startAsync()` method of the `ServletRequest` object allows developers to start asynchronous operations.
• Timeout Configuration: Using the `setTimeout()` method, developers can specify a timeout for asynchronous operations in the `AsyncContext`.

23. Why is the HttpSessionListener interface used?

Ans:

Java Servlets use the HttpSessionListener interface as a way to react to and receive notifications regarding modifications to HttpSession object lifecycles. Developers can build custom logic to run on session creation, invalidation, and addition or removal events by implementing this interface. Entry points to run code at particular stages of the session’s lifetime are provided by important methods like sessionCreated() and sessionDestroyed().

24. What do servlets’ cookies do?

Ans:

Cookies, as used in Servlets, are little data files that a web server sends to a user’s web browser when the user first interacts with a website. The client’s computer then stores these cookies. Web apps may identify and follow users over numerous requests thanks to cookies, which act as a means for permanently storing user data. Session IDs, user preferences, and any other data that must be kept between visits can all be included in this information.

25. Describe how the Cookie class’s setMaxAge() function works.

Ans:

The maximum age of a cookie in seconds can be set using the `setMaxAge()` function in the `Cookie` class. Developers can specify how long a cookie should remain on a client’s computer by using this mechanism. An explicit expiration period in seconds is set by a positive value, after which the cookie will be deleted automatically.

26. What does the web.xml file’s security-constraint element serve as?

Ans:

Determining security constraints and access rules for particular web sites is mostly dependent on the security-constraint element found in the web.xml file of a Java web application. An explanation of its goal is provided below:

• Web Resources and URL Patterns: Developers can link particular URL patterns or groupings of online resources to security constraints.
• Auth constraints: Auth-constraint elements are used inside security-constraint elements to specify which roles or users are allowed access to the protected resource.
• User Data Constraints: Whether or not to encrypt sensitive data before transmission is determined by the user-data-constraint element within a security-constraint.

27. Describe the distinction between RequestDispatcher and RequestDispatcher.forward().incorporate().

Ans:

When you use forward() to move control to another resource, the first request and answer are deleted. Without deleting the existing response, include() incorporates the content of an additional resource into the response.

28. Explain the FilterChain In Servlets.

Ans:

The FilterChain is an important component of Servlets that allows for the organised execution of several filters in a web application. Filters intercept requests and responses, allowing developers to conduct preprocessing and postprocessing activities. The FilterChain object is supplied to each filter’s doFilter() method, allowing control to flow from one filter to the next.

29. What exactly is a Servlet Filter and why do we need one?

Ans:

A Servlet Filter is used to conduct filtering operations on a resource’s request, response, or both. Authentication, logging, and altering request/response headers are common uses.

30. What is the ServletContextListener interface for?

Ans:

The ServletContextListener interface in Servlets is critical for monitoring and responding to changes in a web application’s servlet context. Developers can define custom logic that runs when the servlet context is initialised or deleted by implementing this interface. Key methods like contextInitialized() and contextDestroyed() give entry points for running code at certain moments in the servlet context’s lifetime.

31. What is the Servlet application’s web.xml file used for?

Ans:

A Servlet application’s web.xml file acts as the deployment descriptor, giving the servlet container the necessary configuration information and parameters to deploy and administer the web application. Here is a summary of its main responsibilities:

32. Describe the distinction between sendRedirect() and a RequestDispatcher.

Ans:

SendRedirect() is used to reroute the client to another URL, whereas RequestDispatcher is used to transmit the request to another resource on the server. These are the main things of the distinction

• The server-side `RequestDispatcher` facilitates multi-servlet cooperation during request processing.
• A new round-trip between the client and the server is initiated by the `sendRedirect()` function, which entails a new request from the client’s browser.

33. How do asynchronous Servlets work?

Ans:

Better concurrency and responsiveness in web applications are made possible by Java’s asynchronous servlets, which offer a way to manage laborious activities or tasks without blocking the request thread. Instead of stopping the thread until the asynchronous task is finished, an asynchronous servlet permits the request thread to be returned to the container while it waits for the task to finish.

34. In Servlets, how can file uploads be handled?

Ans:

Configuring the HTML form to utilise the multipart/form-data encoding type—which is intended especially for conveying binary data, like files—is the first step in handling file uploads in Servlets. Third-party libraries are also frequently used by developers to streamline the process. Apache Commons FileUpload is a widely used library in Servlets for managing file uploads.

35. Describe the purpose of the web.xml and elements.

Ans:

A Java web application’s servlet is defined using the element in the web.xml file. It offers an option to set various options, initialization parameters, and the servlet class.

• A servlet can be mapped to a URL pattern using the element, which specifies which URLs the given servlet should handle.
• The servlet called “MyServlet” in this instance is mapped to the URL pattern “/myservlet.” The servlet defined in the element will be invoked to handle requests made by clients to the “/myservlet” URL.

36. Describe the web.xml file’s function in Servlet security.

Ans:

A Java online application’s web.xml file is essential for specifying security settings, especially when it comes to Servlet security. Developers are able to set login preferences, define security roles, and impose restrictions on access to different resources. The web.xml file’s security-constraint element is particularly crucial for defining which users or roles have the authority to access particular areas of the programme.

37. Describe how to configure the content type in Servlets for file downloads.

Ans:

Developers utilise the response to set the content type for file downloads in Servlets.Using the setContentType(“application/octet-stream”) function. This line of code instructs the browser to handle the material being supplied as a file to be downloaded rather than displayed because it is binary data.

38. How may JSP and Servlets be combined?

Ans:

The actions <'jsp:include'> and <'jsp:forward'> allow for the smooth integration of Servlets and JSP. These steps make it possible for servlet-generated material to be included or forwarded within JSP pages. The <'jsp:include'> element facilitates code reuse and modularization by enabling developers to integrate servlet output within a JSP page. Alternatively, dynamic content generation can be enabled by using the <'jsp:forward'> tag, which forwards control from a JSP page to a servlet.

39. In Servlets, how are concurrent requests handled

Ans:

• Shared Resources: Developers are responsible for locating and controlling shared resources, like data structures or instance variables, that several threads may use simultaneously.
• Thread-Safe Design: Servlets, particularly those that hold state, ought to be made with thread safety in mind.
• Synchronisation: To manage access to crucial code segments involving common resources, use synchronisation mechanisms, such as synchronised methods or blocks.

40. How may the performance of Servlets be enhanced?

Ans:

Reduce the amount of synchronisation used, optimise database queries, and employ connection pooling to increase servlet performance. Developers may guarantee that servlet-based applications provide the best possible responsiveness and resource utilisation by implementing these performance optimisation approaches.

41. Describe the idea behind servlet threading.

Ans:

When several requests are executed concurrently in a servlet container—each servlet instance having its own thread—this is referred to as servlet threading. A distinct thread is allocated for every incoming request by servlet containers, like Tomcat or Jetty, to control the execution of servlets. Because servlets can handle numerous requests at once thanks to this multithreading technique, the application will respond more quickly.

42. What does the @WebServlet annotation mean?

Ans:

In Java Servlets, a servlet can be declared without utilising the conventional web.xml deployment descriptor by using the @WebServlet annotation. With the use of this annotation, developers can declare servlets directly in the servlet class, streamlining and condensing the setup. The main goal of @WebServlet is to eliminate the requirement for an external XML configuration by specifying the URL patterns for which the servlet should be executed.

43. What is the ServletContext property used for?

Ans:

Java Servlets provide a means for data and information sharing between various components of a web application through the `ServletContext` attribute.

• Global Storage: Data for the entire web application can be globally stored in the `ServletContext`, which acts as a central storage location.
• Initialization Parameters: Servlets and other components can use the `getInitParameter()` method of `ServletContext` to obtain initialization parameters that are declared in the `web.xml` deployment descriptor.

44. Describe the Servlets Single Thread Model.

Ans:

In the initial iterations of Servlets, an interface known as the Single Thread Model was created to ensure that a servlet processes a single request at a time. Because the servlet container would synchronise access to the `service()` method, guaranteeing that only one request could be processed at any given time, servlets implementing this interface were regarded as thread-safe.

45. What does the `response.sendRedirect()` method accomplish?

Ans:

Java Servlets employ the `response.sendRedirect()` method to send a redirect response to the client’s browser. By doing this, the browser is told to send a fresh request to the given URL. This method’s main goal is to start a client-side redirection, which directs the browser to another URL or resource.

46. In a Servlet, how are attributes set and retrieved?

Ans:

ServletRequest and HttpSession objects provide methods called `setAttribute()` and `getAttribute()` that can be used to set and get attributes in a servlet.

47. What distinguishes a `POST` request from a `GET` request?

Ans:

When requesting data from a designated resource, one uses a `GET` request, where the arguments are part of the URL. When submitting data to be processed to a designated resource, a `POST` request is utilised, with parameters contained within the request body.

48. What is the best way to manage sessions in a clustered system?

Ans:

The problem of ensuring consistency of session data across servers must be addressed when handling sessions in a clustered context. These are typical methods:

• Replication of Sessions: Replicate session data among the cluster’s several machines. Upon receiving a request, a server first determines whether the necessary session data is locally accessible.
• Adherent Sessions (Affinity Sessions): By sending all of a user’s requests to the same server during their session, sticky sessions can be implemented.
• Centralised Storage of Session Data: Keep session data in a shared, centralised area, either a database or an external caching solution (like Redis).

49. Describe the idea behind a servlet container.

Ans:

One essential part of a web server or application server that controls the Java Servlet execution and runtime environment is a servlet container, sometimes referred to as a servlet engine. Important features of the Servlet container include of:

• Life Cycle Management: The instantiation, initialization, execution, and destruction of servlets are all managed by the servlet container.
• Request Processing: Incoming HTTP requests are processed and handled by servlet containers.
• Support for Multithreading: Servlet containers can process several requests at once by using multithreading.

50. How do you manage shared resource concurrent access in Servlets?

Ans:

Thread-safe data structures or synchronisation techniques like the `synchronised` keyword can be used to manage concurrent access to shared resources. Performance bottlenecks and deadlocks should be avoided at all costs.

51. Could you describe the stages of a servlet’s life cycle?

Ans:

The steps of initialization, service, and destruction make up the servlet life cycle. The methods `destroy()`, which is performed when the servlet is being pulled out of service, `service()` for each client request, and `init()` are called during initialization.

52. Describe the function of the servlet web.xml deployment descriptor.

Ans:

In the context of Java Servlets, the `web.xml` deployment descriptor is essential for setting up and specifying the structure of a web application. This XML file contains crucial information that instructs the servlet container on how to handle, deploy, and manage the application in its many forms.

53. What distinguishes a servlet from a conventional CGI programme?

Ans:

The following are the ways that a servlet is different from a conventional CGI (Common Gateway Interface) programme:

• Platform Independence: Java is used to write servlets, which are platform-neutral. They offer great mobility because they can operate on any server that is compatible with the Java Servlet API.
• Performance-wise, servlets perform better than CGI programmes in most cases. Because servlets are long-lived and run inside the server’s process.
• Communication overhead between the web server and the servlet container is decreased when servlets use a direct method call to communicate with the server.

54. What are the mechanisms for session management in servlets and how does it operate?

Ans:

One essential component of servlets that enables web applications to retain stateful user interactions across requests is session management. Servlets use a number of methods to accomplish session management, including:

• Cookies are little data files that are transferred from the server to the client’s browser and stored there.
• URL Rewriting: This technique entails adding session data to URLs.
• Servlets have the ability to include the session ID in the URL, which will be included in all further client requests.

55. What is the `ServletContextListener` interface used for?

Ans:

The Java Servlet API provides a means for listening to and reacting to changes in a web application’s servlet context through the `ServletContextListener` interface. This interface’s main objective is to enable developers to carry out cleanup or initialization operations at the startup or shutdown of the application. It is a crucial part of maintaining the servlet context’s lifecycle.

56. Describe how servlets employ filters.

Ans:

When it comes to Java Servlets, filters are an incredibly strong and adaptable tool for processing requests and answers as they go through the servlet container. Filters offer a centralised and reusable method for developers to enhance the functionality of servlets by carrying either pre- or post-processing operations on the content of a request or response.

57. What is the purpose and usage of the `AsyncContext` interface?

Ans:

58. How can servlets handle file uploads?

Ans:

Processing HTML forms with the multipart/form-data encoding type is required when handling file uploads in servlets. Here’s a quick rundown:

• Setting Up an HTML Form: Set the `enctype` element of the HTML form that accepts file uploads to “multipart/form-data.”
• Processing Servlets: Utilise a library such as Apache Commons FileUpload in the servlet to manage the multipart request processing.
• Managing File Content: After determining which FileItem the file upload belongs to, access its InputStream and take any necessary action with the file content.

59. For a servlet-based application, how can SSL be enforced?

Ans:

A servlet-based application must enforce SSL (Secure Socket Layer) in order to secure data transmission between clients and the server. Use in web.xml and configure the web server. The goal of both strategies is to guarantee that private or sensitive data is sent securely over HTTPS, such as login credentials.

60. What kinds of load balancing are possible and how does it operate?

Ans:

In a servlet container, load balancing distributes client requests among several servers in order to maximise resource efficiency, improve scalability, and guarantee high availability. Several load balancing methods and algorithms are used to provide effective distribution.

61. How can the performance of a servlet container be optimised?

Ans:

Optimising web applications’ performance and responsiveness requires fine-tuning servlet containers. The servlet container can be tuned by adjusting a number of important parameters:

• Thread Pool Configuration: Change the thread pool’s size according to the application’s requirements and anticipated load.
• Memory Allocation: Adjust memory settings to guarantee effective memory use and avert memory-related problems.

62. In what ways may servlets work with other technologies RESTful services or JSP?

Ans:

By utilising particular mechanisms designed for each integration, servlets can work along with other technologies like JSP (JavaServer Pages) and RESTful services in an efficient manner:

• Collaboration with JSP: To keep the presentation logic (JSP) and business logic (servlet) distinct, servlets frequently work in tandem with JSP.
• Cooperation with RESTful Services: Servlets can use the common HTTP methods (GET, POST, PUT, DELETE, etc.) to interact with RESTful services.

63. Give an example of how you improved servlet performance in a live setting.

Ans:

There was a web application I came across in a production setting where concurrent requests and a growing user base made servlet performance a major concern. Following a comprehensive performance analysis, I determined that the two main bottlenecks are the optimisation of database queries and the improvement of caching strategies.

64. In the event that a vital servlet-based application experiences an outage, how would you respond?

Ans:

Describe a methodical approach to determining the underlying problem, liaising with relevant parties, putting a temporary remedy in place if required, and resolving the issue to reduce downtime.

65. Give a example leading a team through a significant servlet-based application migration or upgrade?

Ans:

I oversaw a team during a significant servlet-based application upgrade and migration in a previous position. The application, which acted as the foundation for multiple services, was an essential part of our company’s infrastructure. Modernising the technological stack, improving performance, and adding new features were the goals of the migration.

66. How everyone maintains code quality and adheres to best practices in servlet development?

Ans:

It takes a combination of procedures, resources, and a cooperative team culture to guarantee that a team adheres to best practices in servlet development and preserves code quality:

• Code Reviews: To ensure that servlet development adheres to design principles, best practices, and coding standards, conduct code reviews on a regular basis.
• Constant Integration (CI): Put in place a continuous integration (CI) system to automate the build and integration process and guarantee ongoing validation of code modifications.
• Coding Standards and Guidelines: Create explicit coding standards and guidelines that are unique to servlet development, and document them.

67. What ways can a cross-functional team consisting of system administrators, testers, and efficient communication?

Ans:

Project success depends on fostering cooperation and good communication among servlet developers, testers, and system administrators in a cross-functional team. The following are some tactics:

• Frequent gatherings of the team: Call frequent team meetings to go over project status, tackle problems, and provide updates.
• Collaborative Tools: To enable real-time communication and document sharing, make use of collaboration tools including project management platforms.
• Shared Documentation: Ensure that all team members have access to thorough, shared documentation.

68. What are tracking sessions?

Ans:

In web development, session tracking is a technique used to preserve state data about a user’s interactions with a web application over the course of several requests. It allows user-specific data to be persistent by letting the server associate several requests from the same user.

69. Describe cookies.

Ans:

Cookies are little bits of information that a website stores in the user’s browser. They are employed to collect additional data, record user preferences, and monitor user sessions. Cookies give websites the ability to recall visitors and their activities, making browsing more effective and personalised.

70. What does servlet load-on-startup mean?

Ans:

When a servlet configuration in the web.xml file has the `load-on-startup` element, it means that the servlet should load immediately at application startup instead of waiting for the initial request. Lower `load-on-startup` values are loaded first when the servlet container initialises and loads servlets.

71. How would we handle a negative load value at startup?

Ans:

A negative value for load-on-startup signifies that the servlet shouldn’t be loaded when the application first launches. Rather, when that servlet receives its first request, it will load.

72. How do you define a war file?

Ans:

When distributing and deploying a collection of online resources—such as HTML pages, JSP (JavaServer Pages) pages, servlets, classes, libraries, and other relevant files—a WAR (online Application Archive) file is the packaging format of choice. It makes it easier to install web apps on web servers that support Java.

73. When a session is created and destroyed, which event is fired?

Ans:

Two ways are available for processing session creation and deletion events using the `HttpSessionListener` interface:

• `sessionCreated(HttpSessionEvent se)`: Called upon creation of a new session.
• When a session is about to expire or be invalidated, the function `sessionDestroyed(HttpSessionEvent se)` is called.

74. Why is the welcome-file-list used?

Ans:

A list of default files that the web server should search for when a client requests a directory is specified by the `welcome-file-list` element in the web.xml file. In case no specified resource, like http://example.com/mywebapp/, is requested, the web server will try to provide any file mentioned in the `welcome-file-list`.

75. What use do attributes serve in servlets?

Ans:

Attributes in servlets are used to store and retrieve data that can be shared between various web application components. In servlets, characteristics come in three different varieties:

• Request Attributes: Scoped to a particular request.
• Session Attributes: Scoped to a user’s session.
• Context Attributes: Scoped to the entire web application.

76. What distinguishes PrintWriter from ServletOutputStream?

Ans:

• PrintWriter: Character text is sent to the client primarily using this device. Ideal for creating textual content such as HTML and XML. offers handy formatting tools such as `println()`. uses the platform’s default character encoding to internally convert characters to bytes.
• ServletOutputStream: This is where binary data is sent to the client. Ideal for delivering files, pictures, or any other type of non-textual content. requires encoding and explicit processing of binary data. gives a raw byte stream without carrying out any character encoding.

77. What distinguishes an HTTP Servlet from a Generic Servlet?

Ans:

• A generic servlet is an abstract class found in the package javax.servlet. doesn’t offer any particular assistance with HTTP requests. Subclasses must override methods in order to handle requests.
• Generic Servlet is extended by HTTP Servlet. offers specialised assistance for managing HTTP requests. incorporates functions for managing HTTP GET and POST requests, such as `doGet()` and `doPost()`.

78. What does the code sample that follows in an XML file represent?

Ans:

• Indicates that when the web application launches, the related servlet should be loaded.
• The sequence in which servlets are initialised is determined by the numerical value (1 in this case), with lesser values being initialised first.

79. Describe the MVC pattern.

Ans:

A design pattern called Model-View-Controller (MVC) divides an application into three interrelated parts.

• Model: Describes the data and business logic of the application. refreshes the view, handles data, and reacts to information requests.
• View: Provides the user with data displays and transmits user input to the controller.
• Controller: Takes user input and starts modifying the view or model.

80. Is it possible to induce a deadlock in a servlet?

Ans:

Servlets are generally single-threaded programmes, and it is difficult to cause a deadlock within a servlet itself. A higher frequency of deadlocks occurs in multi-threaded contexts. In order to safely handle concurrent requests, servlet containers internally control threading.

81. What does MIME type mean to you?

Ans:

A file’s MIME (Multipurpose Internet Mail Extensions) type is a label that indicates the kind of data contained within. It is used to define the kind of material that the server sends to the browser in web development. For instance, “text/html” refers to HTML files, and “image/jpeg” to JPEG pictures.

82. How is a servlet created and executed?

Ans:

• Initialization: Upon startup, the servlet container loads and sets up the servlet.
• Request handling: The servlet container uses the corresponding method (such as `doGet()} or `doPost()`) in response to the type of HTTP request.
• Processing: Servlets carry out business logic, retrieve data, process requests, and communicate with models.
• Response Generation: Servlet uses either ServletOutputStream or PrintWriter to generate the content of the response.

83. What is the object called ServletConfig?

Ans:

An object called `ServletConfig` contains a servlet’s configuration data. Every servlet’s web container creates it during initialization. It offers the parameters and initialization data found in the deployment descriptor (web.xml) that are provided in the servlet configuration.

84. What does “interServlet communication” imply to you?

Ans:

• InterServlet communication is the exchange of information within a web application between various servlets.
• Request forwarding, request attributes, session attributes, and application-level scope (ServletContext) are some of the technologies that can be used to do this.

85. When you say “Servlet Chaining,” what do you mean?

Ans:

• To handle a client request, several servlets are linked together in a process known as servlet chaining.
• It is possible to send an input from one servlet to another.
• Attained by employing techniques such as `RequestDispatcher.forward()`.

86. Describe the procedures for creating JDBC connections.

Ans:

• JDBC package import: Bring in the required JDBC packages, such as {java.sql.*}.
• JDBC driver loading and registration: Install and set up the JDBC driver that is compatible with your database.
• Create a Connection: To connect to the database, use {DriverManager.getConnection(url, username, password)}.
• Make a statement: To run SQL queries, create an object called `Statement` or `PreparedStatement`.

87. How does one go about inserting a servlet into a package?

Ans:

• Create a directory structure: that corresponds to your servlet’s package hierarchy. If your servlet, for instance, is a part of the package com.example.servlets
• Locate Servlet Source File: Make sure the servlet source file is saved in the right directory. if the name of your servlet is `MyServlet}.
• Put the package declaration in there: Now that your `MyServlet.java` file is open, add the package declaration at the top.

88. How can a servlet be used to produce a cookie?

Ans:

`HttpServletResponse` object in order to transmit the cookie to the client’s browser and set it. A cookie is a little bit of information sent by the server to the client, which is stored in the client’s browser for use in subsequent requests to the same server. In order to store the data, a `Cookie} object representing the name-value pair must first be instantiated. This data may include user-specific information like a username or preferences.

89. What distinguishes a context attribute from a context parameter?

Ans:

Parameter for Context:

• Set up in the file web.xml.
• Pertains to the complete online programme.

Context Attribute:

• Using the `ServletContext` object, set and retrieve programmatically.
• Open to every servlet within the web application.

90. Describe Pure Servlet.

Ans:

A “Pure Servlet” is a term used to describe a servlet-based web development methodology that exclusively uses Java servlets and excludes the use of frameworks or any supplementary technologies such as JavaServer Pages (JSP). Servlets are Java classes that increase a server’s capacity to process client requests and produce dynamic content.

91. How is JSP translated?

Ans:

Servlets are usually generated from JavaServer Pages (JSP) in the first stage of execution. JSP files are translated into corresponding servlets during the translation process, and the servlet container subsequently compiles and runs the servlets. The dynamic content supplied in the original JSP file is produced by the servlet code that results from this translation, which is carried out automatically by the JSP container or server.

92. In servlet, how can a session be created?

Ans:

• Obtain the session object for HTTP: From the `HttpServletRequest`, obtain the `HttpSession` object. This can be accomplished by utilising the `getSession()` method, and if a new session is needed, optionally passing {true}.
• Assign Session Properties: To store properties that must be kept during the session, use the `setAttribute()` method of the `HttpSession` object.
• Acquire Session Properties: In future queries, retrieve session characteristics as needed.

93. Which interface should every servlet implement?

Ans:

The `javax.servlet.Servlet` interface ought to be implemented by every Java servlet. The methods that a servlet class has to implement in order to reply to client requests are specified by the `Servlet` interface. It has functions that let servlets initialise, process requests, and free up resources, like `init()`, `service()`, and `destroy()`.

94. What new features does Servlet 2.5 offer?

Ans:

The Java Servlet API received a number of enhancements and new features with Servlet 2.5. Among the noteworthy contributions are:

• Java annotations (`@WebServlet}, `@WebFilter}, etc.) may now be used to annotate Servlets, which eliminates the need for a lot of setup in the deployment descriptor (web.xml).
• Security through Programming: Annotations allow security limitations to be defined programmatically in the servlet code.
• The advent of web fragments, which let libraries and frameworks add to the web.xml configuration without changing the primary deployment descriptor, is known as web fragmentation.

95. How long does a Servlet unload?

Ans:

When the application terminates or the container chooses to recover resources, the servlet container unloads the servlets. When a servlet is being pulled out of service, the `destroy()` method within the servlet lifecycle is invoked. By using this technique, the servlet can release any resources it is holding, including thread pools and database connections.