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Table of contents
1.
Introduction to J2EE
2.
J2EE Interview Questions for Freshers
2.1.
1. What is J2EE?
2.2.
2. What is a servlet?
2.3.
3. What is a JSP?
2.4.
4. What is EJB?
2.5.
5. What is JMS?
2.6.
6. What is JTA?
2.7.
7. What is JPA?
2.8.
8. What is the difference between stateful and stateless session beans?
2.9.
9. What is the difference between a session and a cookie?
2.10.
10. What is the role of JMS in J2EE?
3.
Intermediate Level J2EE interview questions
3.1.
11. What are the components of J2EE?
3.2.
12. What is the difference between a local and a remote interface in EJB?
3.3.
13. What is the purpose of the Java Persistence API?
3.4.
14. What are a JNDI lookup and JDBC driver?
3.5.
15. What is the purpose of the web.xml file in a J2EE web application?
3.6.
16. What is a servlet filter?
3.7.
17. What is the difference between a JTA transaction and a JDBC transaction?
3.8.
18. What is a JAX-RS API?
3.9.
19. What is the purpose of the @Transactional annotation in Spring?
3.10.
20. What is the difference between a stateless and a stateful session bean?
4.
Advanced Level J2EE interview questions
4.1.
21. How would you design a large-volume email notification system using J2EE?
4.2.
22. How would you identify causes for performance issues in a J2EE application?
4.3.
23. What is the difference between JAX-WS and JAX-RS?
4.4.
24. What is a container-managed transaction?
4.5.
25. What is a security realm in J2EE?
4.6.
26. What is the purpose of the @PreDestroy annotation in a J2EE application?
4.7.
27. What is the difference between a JTA transaction and a local transaction?
4.8.
28. What is a Java EE Connector Architecture (JCA) adapter?
4.9.
29. What is the difference between EJB and POJO?
4.10.
30. What is the role of a deployment descriptor in a J2EE application?
5.
Conclusion
Last Updated: May 30, 2024
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J2EE Interview Questions

Author Tashmit
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Introduction to J2EE

J2EE (Java Enterprise Edition) standards, introduced by Oracle (formerly Sun Microsystems), provide a framework and set of APIs for developing scalable, secure, and portable enterprise-level applications. Key technologies in J2EE include JSP and Servlets, which simplify the creation of large-scale business applications. 

J2EE Interview Questions

In this article, we will get to know the J2EE interview question. J2EE, an abbreviation of Java 2 Platform Enterprise Edition, is a platform independently used to develop, build and deploy a web-based enterprise online application. Let us look at beginner-level, intermediate-level, and advanced-level J2EE interview questions.

Read About, AEM Interview Questions

J2EE Interview Questions for Freshers

1. What is J2EE?

Answer: Java 2 Platform Enterprise Edition is used to develop, build and deploy a web-based enterprise online application. It includes many components, such as servlets, JSPs, EJBs, and JMS, which help developers build scalable and reliable enterprise applications.

2. What is a servlet?

Answer: A servlet is a Java class that can dynamically develop content for web pages. It is a server-side component that receives and responds to HTTP requests from clients. Servlets are commonly used to create content dynamically, such as displaying information from a database or processing user input.

You can know more about What is Servlet here.

3. What is a JSP?

Answer: Java Server Pages is a technology for creating a dynamic, server-side web page. It allows developers to embed Java code into HTML pages, making it easier to build dynamic content. JSP pages are rephrased into servlets and then compiled to bytecode, which can be executed on the server side.

4. What is EJB?

Answer: Enterprise Java Beans is a server-side component architecture for building distributed, transactional, and scalable enterprise applications. EJB components are written in Java and are managed by the EJB container, which provides services such as transaction management, security, and persistence.

5. What is JMS?

Answer: Java Message Service, a specification for messaging between Java applications. It defines a standard set of APIs for sending and receiving messages between two or more clients using a synchronous or asynchronous communication model.

6. What is JTA?

Answer: JTA stands for Java Transaction API, a specification for managing distributed transactions in Java applications. It allows multiple resource managers, such as databases or messaging systems, to participate in a single transaction, ensuring that all the operations are completed or rolled back as a single unit of work.

7. What is JPA?

Answer: JPA stands for Java Persistence API, a specification for object-relational mapping in Java applications. It provides standard APIs for mapping Java objects to database tables and performing CRUD operations on the database. It allows developers to write database-agnostic code and reduces the amount of boilerplate code needed to manage database interactions.

8. What is the difference between stateful and stateless session beans?

Answer: Stateful session beans are EJB components that maintain a conversational state with the client. This means they can store data related to a particular client and carry it across multiple method invocations. In contrast, stateless session beans are EJB components that do not maintain any state across numerous method invocations. They are often used for processing one-off requests or performing small, stateless tasks.

9. What is the difference between a session and a cookie?

Answer: A session is a logical object created by the web container to maintain the state of a user's interaction with a web application. It can store user-specific data on the server side, and the user can access it throughout their session with the application. On the other hand, a cookie is a small text file stored on the client side that can be used to store user-specific data. The server sends it to the client's browser, and the browser keeps it locally.

10. What is the role of JMS in J2EE?

Answer: Java Messaging Service is a standard messaging API that allows Java applications to send and receive messages asynchronously. It is used to decouple the components of a distributed application, allowing them to communicate without needing to know the details of each other's implementation. JMS can be used to implement publish/subscribe, point-to-point, and request/reply messaging patterns.

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Intermediate Level J2EE interview questions

11. What are the components of J2EE?

Answer: The main components of J2EE are as follows:
 

  • Servlets: Java classes that dynamically generate content for web pages.
     
  • Java Server Pages: a technology for creating dynamic, server-side web pages.
     
  • Enterprise JavaBeans (EJB): components that encapsulate the business logic of an application.
     
  • Java Messaging Service: a messaging standard that allows Java applications to send and receive messages asynchronously.
     
  • Java Naming and Directory Interface (JNDI): a standard for accessing naming and directory services.
     
  • Java Transaction API: a standard for managing distributed transactions.

12. What is the difference between a local and a remote interface in EJB?

Answer: A local interface is used for EJBs accessed within the same JVM (Java Virtual Machine) as the client application. This means that the client and the EJB are running in the same process space, so there is no need for network communication. In contrast, a remote interface is used for EJBs accessed from a different JVM or a client application running on another machine. This requires network communication, so a remote interface defines a set of methods that can be accessed over the network.

13. What is the purpose of the Java Persistence API?

Answer: The Java Persistence API specifies Object-Relational Mapping in J2EE. It provides a standard way to map Java objects to database tables and perform CRUD operations on the database. JPA reduces the boilerplate code (boilerplate code is the part of code that can be used multiple times at different places) that is used to manage database interactions and allows developers to write database-agnostic code. 

14. What are a JNDI lookup and JDBC driver?

Answer: Java Naming and Directory Interface (JNDI) is a Java API that provides naming and directory functionality. A JNDI lookup can locate a named object in a distributed environment.

Java Database Connectivity is a Java API used to interact with relational databases. A JDBC driver is a software component that enables Java applications to interact with a specific type of database. JDBC has four types of drivers: Type 1, Type 2, Type 3, and Type 4.

15. What is the purpose of the web.xml file in a J2EE web application?

Answer: The web.xml file is a deployment descriptor for a J2EE web application. It contains information about the web application, such as servlets, filters, and context parameters.

16. What is a servlet filter?

Answer: A servlet filter is a component that intercepts HTTP requests and responses to perform additional processing on them. It is used for authentication, logging, and URL rewriting tasks.

17. What is the difference between a JTA transaction and a JDBC transaction?

Answer: The difference between JTA and JDBC transactions are as follows:

AspectJTA transactionJDBC transaction
TransactionsJTA transactions can involve multiple transactional resources such as databases, message queues, and other services that support transaction managementJDBC transactions are limited to a single database.
AbstractionIt provides a higher-level transaction management API, allowing the application to coordinate transactions across multiple resources.

It provides a lower-level transaction management API limited to a single database.

 

ConcurrencyIt uses optimistic concurrency control, which allows multiple transactions to execute concurrently and commit changes at the end of the transaction.It uses pessimistic concurrency control, which locks the database resources until the transaction is completed.

18. What is a JAX-RS API?

Answer: Java API for RESTful Web Services is a Java programming language API for creating RESTful web services. It is a standard Java API for building web services that follow the REST (Representational State Transfer) architectural pattern. REST is a lightweight architecture based on the HTTP protocol and is used to make web services easy to use, scalable, and maintainable.

19. What is the purpose of the @Transactional annotation in Spring?

Answer: The @Transactional annotation is used in Spring to mark a method as transactional. It specifies the transactional behaviour of the process, such as the propagation level, isolation level, and rollback rules.

20. What is the difference between a stateless and a stateful session bean?

Answer: A stateless session bean does not maintain any conversational state with a client, whereas a stateful session bean keeps a conversational shape across multiple method invocations.

Must Read Web Developer Interview Questions

Advanced Level J2EE interview questions

21. How would you design a large-volume email notification system using J2EE?

Answer: We can use the JavaMail API with a thread pool to parallelly send notifications without blocking the main thread. We can also add a retrying mechanism and an error logger for handling errors.

22. How would you identify causes for performance issues in a J2EE application?

Answer: To address performance issues in a J2EE application, we'd gather performance data using tools like JConsole or New Relic. Then, we'd analyze code and configuration for bottlenecks in SQL queries, caching, and threading. Optimizations like indexing, cache tuning, and thread pooling would also be applied to enhance performance.

23. What is the difference between JAX-WS and JAX-RS?

Answer: JAX-WS (Java API for XML-based Web Services) is a standard Java API for creating SOAP-based web services, while JAX-RS (Java API for RESTful Web Services) is a standard Java API for creating RESTful web services. The critical difference between the two is that JAX-WS is XML-based and relies on the SOAP protocol, while JAX-RS is based on the HTTP protocol and uses JSON or XML to exchange data.

24. What is a container-managed transaction?

Answer: A container-managed transaction (CMT) is managed by the J2EE container rather than by the application itself. In a CMT, the container automatically manages the transaction boundaries, rollbacks, and commit operations, simplifying the application developer's programming model.

25. What is a security realm in J2EE?

Answer: A security realm is a collection of users, groups, roles, and permissions that define the security policies for a J2EE application. The security realm is managed by the J2EE container, which provides a centralized way to authenticate and authorize users and enforce access control policies.

26. What is the purpose of the @PreDestroy annotation in a J2EE application?

Answer: The @PreDestroy annotation marks a method called when a J2EE component is being destroyed. This method can be used to perform cleanup tasks, such as releasing resources, closing database connections, or stopping background threads.

27. What is the difference between a JTA transaction and a local transaction?

Answer: A JTA (Java Transaction API) transaction is a distributed transaction that involves multiple resources, such as databases or messaging systems, and is managed by the J2EE container. A local transaction is a transaction that involves only a single resource and is governed by the application itself.

28. What is a Java EE Connector Architecture (JCA) adapter?

Answer: A JCA adapter is a software component that provides a standard way to connect a J2EE application to a resource, such as a database, an email system, or a legacy system. The adapter implements the JCA specification, which defines the standard interfaces for connecting to a resource and managing transactions, security, and error handling.

29. What is the difference between EJB and POJO?

Answer: EJB (Enterprise Java Beans) is a component model for building server-side business logic. Whereas POJO (Plain Old Java Object) is a simple Java object that is not bound by any specific framework or technology. EJBs offer distributed transactions, security, and concurrency management features, while POJOs are simple and lightweight.

30. What is the role of a deployment descriptor in a J2EE application?

Answer: A deployment descriptor is an XML file that provides configuration information for a J2EE application. It specifies the location of the components, the dependencies between the elements, and the security settings, among other things.

Conclusion

In conclusion, this article discussed a wide range of J2EE interview questions, categorized into basic, intermediate, and advanced levels. These questions are important for anyone preparing for J2EE interviews, as they cover fundamental concepts like servlets, JSPs, EJBs, JMS, and advanced topics such as performance optimization, email notification systems, and security realms. You can check out our other articles:

You can also consider our Interview Preparation Course to give your career an edge over others.

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