Introduction to Java Servlet Interview Questions and Answers
Java Servlet is a web component that is based on Java Enterprise Edition technology. It is a kind of software component that extends the capabilities of a web server or an application server. Servlets handle the requests and responses of a client i.e. a web browser that can be on any platform through a web server or application server. Java Servlets reside in a web container or also called a servlet container where the container handles the requests and redirects or dispatches the responses based on the mapping of the servlets as per the Deployment Descriptor where DD (Deployment Descriptor) is a mapping file that resides and is configured in a web application to map the web requests correctly. DD helps in getting the requests and responses mapped correctly through the webserver.
Now, if you are looking for a job that is related to Java Servlet then you need to prepare for the 2021 Java Servlet Interview Questions. It is true that every interview is different as per the different job profiles. Here, we have prepared the important Java Servlet Interview Questions and Answers which will help you get success in your interview.
In this 2020 Java Servlet Interview Questions article, we shall present 10 most important and frequently asked Java Servlet interview questions. These 2021 Java Servlet interview questions are divided into two parts are as follows:
Part 1 – Java Servlet Interview Questions (Basic)
This first part covers basic Interview Questions and Answers.
Q1. What is a Java Servlet?
A Java Servlet is a web component in which its lifecycle is managed by a servlet container present in a web server. A Servlet is nothing but a simple Java class that extends the features of a Servlet interface by implementing the Java Servlet API by conforming and complying with the Java EE standards. A servlet could establish communication in the form of a client-server protocol. A Servlet is a javax. servlet package which can be used by adding as a dependency or in a library to utilize its functionalities or features.
Q2. What are the features of Servlet?
This is the basic Interview Questions asked in an interview. The different features of a Servlet are –
- It has a dependency on the Java Standard Edition version 5 i.e., J2SE 5.0.
- It supports annotations features that reduce the code complexity and enables loose coupling in code.
- It helps in loading the class using web.xml i.e. called Deployment Descriptor.
- It is portable and easy to use and implement.
- It is robust, efficient and scalable.
- It has different features such as exception handling, garbage collection, security mechanism, etc.,
- It is less prone to memory leaks and memory management faults.
Q3. What are the different phases of Java Servlet Life Cycle?
There are different phases in the Life Cycle of a Java Servlet, they are Initialization of Servlet, Service implementation and Destroying the Servlet. :
- Initialization: In this stage, init() method of the servlet will be called and executed to initialize the servlet.
- Service: In this stage, the service() method of the servlet is called to process the request and return the response to the client through a web server.
- Destroy: In this stage, the destroy() method is called, which is the last phase of the Servlet where the servlet instance or the object will be destroyed and finally it will be garbage collected.
Q4. What are the different functionalities of the Servlet Container?
This is the basic Java Servlet Interview Questions asked in an interview. The below is the list of few functionalities of Servlet Container but are not exhausted :
- It handles the life cycle management of a servlet.
- It supports the communication mechanism between a web browser and the servlet.
- It supports multithreading which in turn supports in the execution of the multiple servlets.
- It has declarative inbuilt security features, JSP (Java Server pages) support.
- It implements java enterprise architecture.
- It supports concurrency, security, transaction, deployment, lifecycle management, automatic garbage collection, and a few other services.
Q5. Explain the architecture of the Servlet Life Cycle?
The different components in the architecture of the Servlet Life Cycle are Servlet, Servlet Container, Web Server, a network established between the servlet container and the client web browser. The different methods of a servlet instance can be called once the servlet is enabled to initialize by the servlet container. Servlet is a thread-safe component. A Servlet Container instantiates different servlets in the form of different threads where each servlet’s lifecycle can be handled in each thread. Many servlet threads can be instantiated and they will be managed by the Servlet Container efficiently. The Servlet Container complies with the Java EE Standards in a Server.
Part 2 – Java Servlet Interview Questions (Advanced)
Let us now have a look at the advanced Interview Questions.
Q6. What is HTTP Servlet?
An HTTP Servlet is a Servlet that supports HTTP protocol and its different HTTP methods such as HTTP GET, HTTP PUT, HTTP POST, HTTP DELETE and HTTP PATCH. The different methods in the Servlet are doGet(), doPost(), doPut(), doTrace(), doOptions(). HttpServlet is an abstract class of the Servlet API. It exists in javax.servlet package. It extends GenericServlet. It will not have any abstract methods in it.
Q7. What is a Servlet Filter?
A Servlet Filter is used to filter the requests and responses of the client in a Servlet Container. This can be implemented by using filter elements in the Deployment Descriptor i.e., web.xml of the web application. It also performs some form of post-processing after filtering the request of the client. Servlet filters are portable and can be easily integrated with the Servlet components which are a kind of pluggable. Filters can be in multiple numbers with to filter the servlet requests and responses. The Servlet Filter lifecycle method are init(), doFilter() and destroy() which are similar to Servlet except the Service() method where the servlet will be initialized, performs filtering operations and destroys the filter instance or object.
Q8. What are the different Servlet Filters?
The different Servlet filters available are Data compression Filters, Authentication Filters, Filters which triggers the resources access events, Encryption Filters, Logging, Auditing Filters, Tokenizing Filters, and Image Conversion Filters.
Q9. What is a Session in Servlet?
This is the popular Java Servlet Interview Questions asked in an interview. A Session is a period of an interval in which the state of the Servlet is maintained in the Servlet Container. This process is called Session Management in the Servlet. Session tracking can also be maintained in Servlet by tracking the state of a user. As HTTP Servlet is stateless, Session can be used along with HttpServlet to maintain HTTP Session.
Q10. What are the different protocols supported by HttpServlet?
The different protocols supported by HTTPSerlvet are HTTP (Hyper Text Transfer Protocol)and HTTPS (Hyper Text Transfer Protocol Secure).
This has been a guide to the list of Java Servlet Interview Questions and Answers so that the candidate can crackdown these Interview Questions easily. Here in this post, we have studied top Java Servlet Interview Questions which are often asked in interviews. You may also look at the following articles to learn more –