Common Servlet Interview Questions (With Sample Answers)

Servlets are an important part of Java EE and web applications. When applying for jobs in this field, the interviewer might ask you questions that require you to have a deep understanding of servlet technology. Having a brief idea of servlet interview questions can increase your chances of getting the job. In this article, we discuss some common servlet interview questions along with their sample answers.

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Commonly asked servlet interview questions

There are various kinds of servlet interview questions that the interviewer may ask you. They may intend to know if you are the right fit for the role for which you are interviewing. Here are some common servlet questions to help you prepare:

1. Describe the life cycle of a servlet.

This may be the first question the interviewer asks. Before getting into in-depth questions, they may try to test your basic understanding of servlets. Consider answering this question by telling them the steps involved in the life cycle of a servlet.

Example: "The life cycle of a servlet comprises the entire process, from its creation to its destruction. It includes steps like loading of a servlet class, creation of a servlet instance, initialising the servlet, requesting the service and finally destroying the servlet."

2. Explain what WAR means.

The interviewer may ask you this question to gauge your understanding of terminologies related to servlets. When you answer this question, start by explaining what WAR means and describe its usage. Make sure you keep the answer brief and precise.

Example: "The word WAR stands for Web Archive. It is used to create compressed versions of web applications and is also helpful in deploying it."

3. Tell us different ways of destroying a servlet session.

The interviewer may ask you this question to test your practical knowledge of the subject. Answer this question by explaining ways of destroying a servlet session. You may consider explaining two or more ways of doing so.

Example: "There are two ways of destroying a servlet session. The first way is to shut down the server. The second way is to use the session.invalidate() method which causes the container to force quit the session."

4. How is servlet chaining performed?

The interviewer may ask you some questions like this to understand if you have some experience in this field. To answer this question, briefly state the process of servlet chaining based on your experience. You may also start by explaining servlet chaining.

Example: "The method of combining two or more servlets to service one request is called servlet chaining. In this technique, programmers often use one servlet's output data as the input of the following servlet. They repeat it till the last servlet is hit. After the last step, the final servlet's output gets delivered to the client."

5. Explain the differences between a session and a cookie.

Interviewers may ask this question to test your knowledge on both topics. Briefly state the difference between both a session and a cookie to prove your understanding of the subject. You can also compare both.

Example: "The primary differences between a session and a cookie are their size and speed. Sessions are stored on the device server while cookies are stored in the client. Besides that, sessions can store large amounts of data whereas cookies can only store strings. Compared to sessions, cookies are much faster."

6. What is a cookie?

This question is likely to come up in your interview for a job involving web applications as cookies are an essential part of the job role. Answer this question by defining a cookie and explaining the types of cookies. You can also consider explaining their usage in depth.

Example: "Cookies are small bits of data stored in the form of text files. They are used to store information like user IDs, passwords and other information that might be helpful in identifying a user's device and network. They also help improve the web browsing experience. All cookies have a unique ID specific to the user's computer. It passes the information to the server which then analyses it to serve the users' needs. There are two different types of cookies, which are HTTP cookies and Magic cookies.

Magic cookie's primary function is to store login information. It is an older version of cookies that stores data and sends it without any changes. Whereas HTTP cookies are an evolved version of the magic cookie which stores the user's browsing information to provide better experiences. Some people may misuse it to track activity or invade a user's privacy."

7. Discuss the advantages of servlet chains.

Servlet chains have many advantages owing to their wide usage. In this question, you can discuss some of the advantages which you may have experienced yourself. This can help the interviewer gain confidence in your abilities.

Example: "Some of the advantages of executing servlet chains as per my experience are that servlet chains make it easy to reverse changes as one can undo them quickly. Besides that, servlet chains do not perform and execute the script each time. Instead, they add the content to the cache for later. Using servlet chains can assist in managing content dynamically. This maintains all restrictions and ensures that it displays postscript images properly."

8. Are servlets better than computer-generated imagery? If yes, why?

Interviewers may be keen to know if you are genuinely interested in the job for which you are applying. To measure your confidence, they may ask you this question to know if you believe that servlets are the better technology. Think about how servlets are better than computer-generated imagery and list those reasons one by one.

Example: "Yes, servlets are better than computer-generated imagery. Servlets are faster than computer-generated imagery as they create threads instead of executing a new process each time. They have complete access to the java class library which computer-generated imagery does not have. Servlets can also communicate with applets, software and databases with the help of java class libraries, which improves their efficiency. Finally, servlets are a safer alternative to computer-generated imagery as they use security restrictions powered by the java security manager."

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9. Why are servlets used widely?

An employer looks for team members that understand the market and latest technologies. They might ask this question to check your awareness of the market. Based on your understanding of servlet, answer this question by stating why are they common compared to other technologies.

Example: "The fact that servlets are platform-independent java classes and are put together to platform-neutral byte code, is why they are popular. One can dynamically upload them to servers, which most professionals prefer."

10. What does a filter mean?

At this stage, the interviewer might want to know if you are aware of certain technical terminologies. Tell the interviewer what a filter is and its usage to answer this question. Try to keep your answer short.

Example: "A filter is a reusable code that enables the transformation of content in the header, response and HTTP requests."

11. Can you explain what servlet mapping is?

Use this opportunity to showcase your deep understanding of the subject. Explain what servlet mapping is and share examples of it. Keep your answer short and precise.

Example: "Servlet mapping enables how we access a servlet. When the client provides a URL, servlet mapping dictates which java servlet to invoke and maps the path to invoke the servlet. One can do it by entering a series of commands that map out the content of the page."

12. Which interface is used by servlets?

Servlet only uses one interface. The interview might ask you this question to test your confidence. Answer this question by naming that interface.

Example: 'All servlets only use the servlet interface.'

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13. What is a session?

To answer this question, define a session in short. This may help the interviewer understand your expertise in the field. You may also define the use of a session.

Example: "A session is used by a servlet to track the user's interaction with the web application through multiple HTTP requests."

15. How is a servlet loaded?

State the steps of loading a servlet to give a well-informed and clear answer to your interviewer. Their intention behind this question is to gauge your practical expertise in the field. Since this is a technical question, try to provide a precise answer in brief.

Example: "A servlet is loaded when the server receives a request. After which, the server starts. Once it answers all the requests correctly, the administrator loads manually."

Read more: Technical Interview Questions And Example Answers

16. What are the benefits of using cookies?

It is important for a programmer to have an in-depth understanding of cookies, which is what the interviewer wants to ensure. Answer this question by mentioning the primary benefits of cookies. You can either keep this answer short or provide details based on your knowledge.

Example: "Cookies enable the storage of information for a long period of time without interacting with the server. It can queue small or medium-size data."

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