1. What is a JavaBeans? Explain with an example.

JavaBeans is a Java-based component model that allows developers to

create reusable, modular components that can be easily integrated into
larger applications. JavaBeans components are typically used to
encapsulate data and business logic, making it easier to develop and
maintain complex systems.
Characteristics of JavaBeans
JavaBeans components have the following characteristics:
1. Encapsulation: JavaBeans components encapsulate data and behavior,
making it easier to modify and extend the component without affecting
other parts of the system.
2. Reusability: JavaBeans components are designed to be reusable,
making it easier to develop and maintain complex systems.
3. Modularity: JavaBeans components are modular, making it easier to
develop and test individual components without affecting other parts of
the system.
4. Configurability: JavaBeans components can be configured using
properties, making it easier to customize the behavior of the component.
Example of a JavaBeans Component
Here is an example of a simple JavaBeans component that represents a
person:
java
public class PersonBean {
private String name;
private int age;
public PersonBean() {}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
}
 2. Write down five differences between JavaBean and EJB (Enterprise
Java Bean).

Here are five key differences between JavaBean and EJB:

1. Purpose:
- JavaBean: A JavaBean is a reusable software component that encapsulates
data and behavior. Its primary purpose is to provide a simple way to create
reusable components.
- EJB: An EJB is a server-side component that provides a way to develop
distributed, transactional, and scalable applications. Its primary purpose is to
provide a robust and scalable way to develop enterprise-level applications.
2. Complexity:
- JavaBean: JavaBeans are relatively simple and lightweight components.
- EJB: EJBs are more complex and heavyweight components that require a
deeper understanding of distributed systems, transactions, and security.
3. Scope:
- JavaBean: JavaBeans are typically used within a single application or
module.
- EJB: EJBs are designed to be used across multiple applications and
modules, and can be deployed across multiple servers.
4. Lifecycle:
- JavaBean: JavaBeans have a simple lifecycle that is managed by the
developer.
- EJB: EJBs have a more complex lifecycle that is managed by the EJB
container. The container is responsible for creating, activating, and passivating
EJB instances.
5. Transaction Support:
- JavaBean: JavaBeans do not provide built-in transaction support.
 - EJB: EJBs provide built-in transaction support, which allows developers to
write transactional code that is managed by the EJB container.

In summary, JavaBeans are simple, lightweight components that are suitable for
developing small to medium-sized applications, while EJBs are more complex,
heavyweight components that are suitable for developing large-scale,
distributed, and transactional applications.

3. Write down about Types of EJB? And also write difference between
Stateful Session bean and Stateless Session bean.

There are three main types of Enterprise JavaBeans (EJB):

1. Stateless Session Bean (SLSB): A stateless session bean does not
maintain any state between method calls. Each method call is
independent, and the bean instance is not associated with a specific client.
2. Stateful Session Bean (SFSB): A stateful session bean maintains its
state between method calls. The bean's state is stored in the bean instance
itself, and the bean instance is associated with a specific client.
3. Entity Bean (EB): An entity bean represents a business entity, such as a
customer or an order. Entity beans are typically used to encapsulate data
and behavior related to a specific business entity.
4. Message-Driven Bean (MDB): A message-driven bean is a type of EJB
that is designed to handle asynchronous messages. MDBs are typically
used to handle JMS (Java Message Service) messages.
Difference between Stateful Session Bean and Stateless Session Bean
Here are the main differences between stateful session beans and stateless
session beans:
Stateful Session Bean (SFSB)
- Maintains state between method calls
- Bean instance is associated with a specific client
- Supports transactions and concurrency control
- More complex and heavyweight than SLSB
Stateless Session Bean (SLSB)
- Does not maintain state between method calls
- Bean instance is not associated with a specific client
- Supports transactions, but concurrency control is not necessary
- Simpler and more lightweight than SFSB
Key differences
- State maintenance: SFSB maintains state, while SLSB does not.
- Bean instance association: SFSB is associated with a specific client,
while SLSB is not.
- Complexity: SFSB is more complex and heavyweight than SLSB.
- Concurrency control: SFSB requires concurrency control, while SLSB
does not.
 In summary, SFSB is suitable for applications that require maintaining
state between method calls, while SLSB is suitable for applications that
do not require state maintenance.

4. What is NPM (Node Package Manager) in Node.js?

NPM (Node Package Manager) is the package manager for Node.js,

allowing developers to easily install, update, and manage dependencies
for their projects.
Features of NPM
1. Package Installation: NPM allows developers to easily install packages
from the npm registry using the npm install command.
2. Dependency Management: NPM manages dependencies for a project
by creating a package.json file that lists the dependencies and their
versions.
3. Package Updates: NPM allows developers to update packages to the
latest version using the npm update command.
4. Package Uninstallation: NPM allows developers to uninstall packages
using the npm uninstall command.
5. Package Publishing: NPM allows developers to publish their own
packages to the npm registry.
Commands in NPM
1. npm init: Initializes a new npm project by creating a package.json file.
2. npm install: Installs a package and its dependencies.
3. npm update: Updates a package to the latest version.
4. npm uninstall: Uninstalls a package.
5. npm publish: Publishes a package to the npm registry.
6. npm run: Runs a script defined in the package.json file.
Benefits of NPM
1. Easy Dependency Management: NPM makes it easy to manage
dependencies for a project.
2. Large Ecosystem: NPM has a large ecosystem of packages that can be
easily installed and used.
3. Easy Package Updates: NPM makes it easy to update packages to the
latest version.
4. Easy Package Publishing: NPM makes it easy to publish packages to
the npm registry.
Example of Using NPM
Here is an example of using NPM to install the Express.js package:
npm install express
This command installs the Express.js package and its dependencies. The
 package.json file is updated to reflect the new dependency.
5. Explain about Callback Concepts Events in Node.js.

Node.js is an event-driven, non-blocking I/O model that uses

callbacks and events to handle asynchronous operations.
Callbacks
A callback is a function that is passed as an argument to another function,
which is then executed when a specific operation is complete. Callbacks
are used to handle asynchronous operations, such as reading a file or
making a network request.
Types of Callbacks
1. Synchronous Callbacks: These callbacks are executed immediately,
blocking the execution of the code.
2. Asynchronous Callbacks: These callbacks are executed at a later time,
allowing the code to continue executing without blocking.
Events
Events are used to notify the application of specific occurrences, such as
the completion of an asynchronous operation. Node.js provides an events
module that allows developers to create and handle events.
Types of Events
1. Synchronous Events: These events are emitted immediately, blocking
the execution of the code.
2. Asynchronous Events: These events are emitted at a later time,
allowing the code to continue executing without blocking.
Event Emitters
Event emitters are objects that emit events. Node.js provides an
EventEmitter class that can be used to create event emitters.
Event Listeners
Event listeners are functions that are registered to handle specific events.
When an event is emitted, the corresponding event listener is executed.
Example of Using Callbacks and Events
Here is an example of using callbacks and events to read a file:
const fs = require('fs');
const EventEmitter = require('events');
class FileReader extends EventEmitter {
constructor(filename) {
super();
 this.filename = filename;
}
read() {
fs.readFile(this.filename, (err, data) => {
if (err) {
this.emit('error', err);
} else {
this.emit('data', data);
}
});
}
}
const reader = new FileReader('example.txt');
reader.on('data', (data) => {
console.log(data.toString());
});
reader.on('error', (err) => {
console.error(err);
});
reader.read();
In this example, the FileReader class extends the EventEmitter class and emits
events when the file is read successfully or when an error occurs. The event
listeners are registered using the on method, and the read method is used to read
the file.

6. What is Node.js and also define about Environment Setup in

Node.js?

Node.js is a JavaScript runtime environment that allows developers to run

JavaScript on the server-side. It provides an event-driven, non-blocking
I/O model that makes it lightweight and efficient. Node.js is built on
Chrome's V8 JavaScript engine and provides a rich ecosystem of
packages and modules that can be easily installed and used.
Node.js is commonly used for:
1. Web Development: Node.js can be used to build fast and scalable web
applications using frameworks like Express.js and Koa.js.
2. Microservices: Node.js can be used to build microservices that
communicate with each other using APIs.
3. Real-time Applications: Node.js can be used to build real-time
applications like chatbots, live updates, and gaming.
4. IoT Development: Node.js can be used to build IoT applications that
interact with devices and sensors.
Environment Setup in Node.js
To set up a Node.js environment, you need to follow these steps:
 1. Install Node.js: Download and install Node.js from the official Node.js
website.
2. Install a Code Editor: Install a code editor like Visual Studio Code,
Sublime Text, or Atom.
3. Install a Package Manager: Node.js comes with a package manager
called npm (Node Package Manager). You can also use yarn as an
alternative package manager.
4. Create a New Project: Create a new project folder and navigate to it in
your terminal or command prompt.
5. Initialize a New Node.js Project: Run the command npm init or yarn
init to create a new package.json file.
6. Install Dependencies: Install dependencies like Express.js, MongoDB,
or other packages required for your project.
7. Write Your Code: Write your Node.js code in a file like app.js or
index.js.
8. Run Your Code: Run your Node.js code using the command node
app.js or node index.js.
Example of a Simple Node.js Project
Here is an example of a simple Node.js project that uses Express.js to
create a web server:
const express = require('express');
const app = express();
app.get('/', (req, res) => {
res.send('Hello World!');
});
app.listen(3000, () => {
console.log('Server started on port 3000');
});

7. What is MongoDB? Explain about different operation on MongoDB

Database, collection and document.

MongoDB is a popular, open-source, document-oriented NoSQL

database that allows for flexible and scalable data storage. It is designed
to handle large amounts of data and provides high performance,
scalability, and flexibility.

Different Operations on MongoDB

Here are the different operations that can be performed on MongoDB

databases, collections, and documents:
Database Operations
1. Create Database: Create a new database using the use command.
Example: use mydatabase
2. Drop Database: Delete a database using the db.dropDatabase()
method.
Example: db.dropDatabase()
3. List Databases: List all databases using the show dbs command.
Example: show dbs

Collection Operations
1. Create Collection: Create a new collection using the
db.createCollection() method.
Example: db.createCollection("mycollection")
2. Drop Collection: Delete a collection using the db.collection.drop()
method.
Example: db.mycollection.drop()
3. List Collections: List all collections in a database using the show
collections command.
Example: show collections

Document Operations
1. Insert Document: Insert a new document into a collection using the
db.collection.insert() method.
Example: db.mycollection.insert({name: "John", age: 30})
2. Find Document: Retrieve one or more documents from a collection
using the db.collection.find() method.
Example: db.mycollection.find({name: "John"})
3. Update Document: Update one or more documents in a collection
using the db.collection.update() method.
Example: db.mycollection.update({name: "John"}, {$set: {age: 31}})
4. Delete Document: Delete one or more documents from a collection
using the db.collection.remove() method.
Example: db.mycollection.remove({name: "John"})

Other Operations
1. Indexing: Create indexes on one or more fields in a collection to
improve query performance.
Example: db.mycollection.createIndex({name: 1})
2. Aggregation: Perform aggregation operations on data in a collection,
such as grouping, sorting, and filtering.
Example: db.mycollection.aggregate([{ $group: { _id: "$name", count:
{ $sum: 1 } } }])