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.
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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