1. What is J2EE?
J2EE stands for Java 2 Platform Enterprise Edition. It is a platform for developing and deploying enterprise-level applications using Java.

2. What are the main components of J2EE?
The main components of J2EE are Java Servlets, JavaServer Pages (JSP), Enterprise JavaBeans (EJB), Java Message Service (JMS), Java Transaction API (JTA), Java Database Connectivity (JDBC), and Java Naming and Directory Interface (JNDI).

3. What is the difference between Java and J2EE?
Java is a programming language, while J2EE is a platform for developing and deploying enterprise-level applications using Java. J2EE includes additional APIs and technologies that are specifically designed for building large-scale distributed applications.

4. What is the role of the Java Servlet in J2EE?
A Java Servlet is a server-side component that processes client requests and generates dynamic web content. It is responsible for handling HTTP requests, running business logic, and generating responses.

5. What is a JavaServer Page (JSP)?
A JavaServer Page (JSP) is a server-side technology that allows developers to embed Java code within HTML pages. JSPs are compiled into servlets during runtime and can dynamically generate web content.

6. What is the difference between a stateless and stateful session bean?
A stateless session bean does not maintain any conversational state with the client between method invocations. Each method invocation is independent and doesn’t rely on previous invocations. In contrast, a stateful session bean maintains conversational state with the client between method invocations.

7. What is object serialization in Java?
Object serialization is the process of converting an object into a byte stream, which can be saved to a file or transmitted over a network. The serialized objects can be reconstructed later by deserializing the byte stream.

8. What is the Java Naming and Directory Interface (JNDI)?
The Java Naming and Directory Interface (JNDI) is a Java API for accessing naming and directory services. It provides a standard way to interact with various naming and directory services, such as Lightweight Directory Access Protocol (LDAP) and Domain Name System (DNS).

9. What is the purpose of the Java Transaction API (JTA)?
The Java Transaction API (JTA) provides a standard way to manage distributed transactions in Java applications. It enables multiple resources (such as databases, message queues) to participate in a single transaction, ensuring atomicity, consistency, isolation, and durability (ACID) properties.

10. What is the difference between JDBC and JNDI?
JDBC (Java Database Connectivity) is an API for accessing relational databases, while JNDI (Java Naming and Directory Interface) is an API for accessing naming and directory services. JDBC is used to interact with databases, whereas JNDI is used to interact with various naming and directory services.

11. What is a Java Message Service (JMS)?
Java Message Service (JMS) is an API for sending and receiving messages between distributed systems. It provides a common way for applications to communicate asynchronously and decouples message producers from consumers.

12. What are the different types of JMS messaging models?
The different types of JMS messaging models are Point-to-Point (P2P) and Publish/Subscribe (Pub/Sub). In the P2P model, messages are sent from a sender to a specific receiver. In the Pub/Sub model, messages are sent from a publisher to multiple subscribers.

13. What is the purpose of an EJB container?
An EJB (Enterprise JavaBean) container provides a runtime environment for deploying and executing EJB components. It manages the lifecycle, concurrency, security, and transactional aspects of EJBs, allowing them to run in a distributed and scalable manner.

14. What are the different types of EJBs?
The different types of EJBs are Session Beans (stateless and stateful), Message-Driven Beans, and Entity Beans.

15. What is the purpose of the deployment descriptor (web.xml) in a J2EE application?
The deployment descriptor (web.xml) specifies the configuration and deployment settings for a J2EE web application. It defines the web components, servlet mappings, security constraints, initialization parameters, and other settings required for the application’s deployment.

16. What is an application server in J2EE?
An application server is a server that provides a runtime environment for executing J2EE applications. It provides services such as database connectivity, connection pooling, security, transaction management, and resource management to the deployed applications.

17. What is the difference between a web server and an application server?
A web server handles HTTP requests and serves static web content, while an application server provides additional services and runtime environment for executing dynamic web applications. An application server can also support web server capabilities.

18. What is the Java EE Connector Architecture (JCA)?
The Java EE Connector Architecture (JCA) defines a standard architecture for integrating Java EE applications with Enterprise Information Systems (EIS) such as databases, messaging systems, and legacy applications. It provides a standard way to connect and interact with these systems.

19. What is an application client in J2EE?
An application client is a type of Java client that directly interacts with the business logic and services provided by the server-side EJB components. It can be a standalone Java program or a desktop application.

20. What is the difference between J2EE and Java Standard Edition (Java SE)?
Java Standard Edition (Java SE) is the core Java platform that provides the foundation for developing general-purpose applications. J2EE, on the other hand, extends Java SE with additional APIs and technologies specifically designed for building enterprise-level applications.

1. What is J2EE?
J2EE (Java 2 Enterprise Edition) is a platform-independent Java-based technology used for developing distributed enterprise-level applications.

2. What are the components of a J2EE application?
A J2EE application consists of the following components:
– Application client
– Web module
– EJB module
– Resource adapter module

3. What is the difference between EJB and Servlet?
EJB (Enterprise JavaBeans) is a server-side component used for developing scalable and secure business applications, whereas Servlet is a Java class used for handling HTTP requests and generating responses.

4. What is the purpose of JNDI (Java Naming and Directory Interface)?
JNDI is used in J2EE applications to locate and access distributed objects, such as EJB components and database connections.

5. Explain the concept of EJB container and its types.
EJB container is a runtime environment responsible for managing the life cycle of EJBs. There are two types of EJB containers:
– Web container: manages the life cycle of Servlets and JSPs, also known as Web components.
– EJB container: manages the life cycle of Enterprise JavaBeans.

6. What are the transaction attributes in EJB?
There are five transaction attributes in EJB:
– Required
– RequiresNew
– Mandatory
– NotSupported
– Supports

7. What is the difference between stateless and stateful EJBs?
Stateless EJBs do not maintain client-specific data between method invocations, while stateful EJBs maintain conversational state with clients between method invocations.

8. What is the purpose of JMS (Java Message Service)?
JMS is a messaging standard used for asynchronous communication between loosely coupled components in a distributed application.

9. What is the difference between JSP and JSF?
JSP (JavaServer Pages) is a technology used for generating dynamic web content. JSF (JavaServer Faces) is a Java-based web application framework that simplifies the development of user interfaces for web applications.

10. Explain the concept of dependency injection in J2EE.
Dependency injection is a design pattern used in J2EE applications to reduce coupling between components. In dependency injection, the dependencies of a component are injected into it rather than being created or looked up by the component itself.

11. What is the purpose of the Web.xml file in a J2EE application?
The Web.xml file is the deployment descriptor for a web application and contains configuration information such as servlet mappings, URL patterns, and security constraints.

12. What is Object Relational Mapping (ORM)?
ORM is a technique used to map data between an object-oriented programming language and a relational database. It simplifies the process of storing, retrieving, and manipulating data in a database using object-oriented approaches.

13. What is the purpose of the DAO (Data Access Object) pattern?
The DAO pattern is used to separate the data access logic from business logic in an application. It provides a consistent and reusable interface for accessing data from various data sources.

14. What are the different types of session tracking in J2EE?
There are three types of session tracking in J2EE:
– Cookies
– URL rewriting
– Hidden form fields

15. What is the purpose of Java EE Connector Architecture (JCA)?
JCA provides a standard way of integrating enterprise information systems and applications with Java EE applications. It allows Java EE applications to interact with Enterprise Information Systems (EIS) using resource adapters.

16. Explain the concept of container-managed security in J2EE.
Container-managed security is a security model provided by the J2EE container. It allows the server to handle authentication and authorization of users without requiring the application to implement security mechanisms.

17. What are the different types of EJBs?
There are three types of EJBs:
– Session beans
– Entity beans
– Message-driven beans

18. What is the purpose of JTA (Java Transaction API)?
JTA provides a standard Java API for managing distributed transactions in a J2EE environment. It allows multiple resources, such as databases and message queues, to participate in a single transaction.

19. Explain the concept of interceptors in J2EE.
Interceptors are used to intercept and modify the business logic of an enterprise application. They can be used to add additional functionality to an application, such as logging, auditing, and exception handling.

20. What is the purpose of JAX-RS (Java API for RESTful Web Services)?
JAX-RS is a Java API used for building RESTful web services. It provides a set of annotations and classes for defining and implementing RESTful APIs in a simple and easy-to-use manner.