Interview Questions
Interview Questions
Java Full Stack Development
Full Stack Development means working on both client-side and server-side of an application, along with database design and deployment.
As a Full Stack Developer, my role includes:
- Designing responsive UI using frameworks like React/Angular
- Developing backend APIs using Java/Node/Python
- Designing and optimizing databases (SQL/NoSQL)
- Handling authentication, security, and performance
- Deploying applications and managing CI/CD pipelines
I also collaborate with product, QA, and DevOps teams to deliver scalable solution
MVC stands for Model-View-Controller, a design pattern commonly used in web development. In Java Full Stack, the Model represents the data and business logic (often implemented using Java and frameworks like Hibernate), the View is the user interface (HTML, CSS, JavaScript), and the Controller manages the communication between the Model and View (Java, Spring).
Spring is a comprehensive framework for Java development. In Full Stack Development, Spring is often used for building the back-end or server-side of applications. It provides features like dependency injection, aspect-oriented programming, and a wide range of modules that simplify the development of enterprise-level applications.
Hibernate is an object-relational mapping (ORM) framework for Java. In Java Full Stack, Hibernate is commonly used to simplify database interactions by mapping Java objects to database tables. It allows developers to work with Java objects rather than SQL queries, making database interactions more intuitive and object-oriented.
RESTful APIs (Representational State Transfer) are used to enable communication between the front-end and back-end components of a web application. In Java Full Stack, developers often use frameworks like Spring Boot to create RESTful APIs. These APIs facilitate the exchange of data between the client (front end) and the server (back end).
JSON (JavaScript Object Notation) is a lightweight data interchange format widely used in Java Full Stack Development. It is used to transmit data between a server and a web application as an alternative to XML. JSON is easy to parse and generate, making it a preferred choice for data exchange in modern web development.
Angular and React are popular front-end frameworks for building interactive user interfaces. In Java Full Stack, these frameworks are often used to create dynamic and responsive front-end applications. They communicate with the back-end (built using Java and Spring, for example) through RESTful APIs, enabling a seamless integration between the front-end and back-end components.
Maven and Gradle are build automation tools used in Java Full Stack Development to manage the project’s build lifecycle. They help in managing dependencies, compiling code, running tests, and packaging the application for deployment. These tools streamline the development process and ensure consistency in project structure.
Dependency injection is a design pattern used in the Spring Framework to achieve loose coupling between components. In Java Full Stack, Spring’s IoC (Inversion of Control) container manages the dependencies of a Java application by injecting the required objects into classes rather than having the classes create the objects themselves. This promotes modularity, testability, and easier maintenance.
Security is crucial in web applications. In Java Full Stack, security measures are implemented at various levels. For example, Spring Security is commonly used to secure the back-end by handling authentication and authorization. On the front-end, secure coding practices, HTTPS, and measures like input validation are implemented to prevent common vulnerabilities such as Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF).
- User sends a request from browser (UI)
- Request goes through frontend routing
- API call is made to backend server
- Backend validates authentication & authorization
- Business logic is executed
- Database is queried
- Response is sent back as JSON
- Frontend updates UI using state management
This flow ensures separation of concerns and scalability.
- Props are inputs passed from parent to child components and are read-only.
- State is managed inside a component and can change over time.
Example:
A UserProfile component receives username as props, while isLoggedIn is state that changes after login.
Props allow reusability, while state controls dynamic behavior.
REST (Representational State Transfer) is an architectural style for building APIs.
Key principles:
Stateless: Each request contains all information
Client–Server: Separation of concerns
Uniform Interface: Standard HTTP methods
Resource-based: Uses URLs to represent resources
Cacheable: Responses can be cached
REST APIs are lightweight, scalable, and widely used.
JWT (JSON Web Token) is used for stateless authentication.
Flow:
- User logs in with credentials
- Server generates JWT containing user info
- Token sent to client
- Client sends token in Authorization header
- Server validates token
Advantages:
- No session storage
- Scalable
- Faster authentication
- Suitable for microservices
SQL databases (MySQL, PostgreSQL):
- Fixed schema
- ACID compliance
- Suitable for financial and transactional systems
NoSQL databases (MongoDB, Cassandra):
- Flexible schema
- Horizontally scalable
- Suitable for big data, real-time apps
Choice depends on data structure, scale, and consistency needs.
Indexes are data structures that improve query performance by reducing data scans.
Advantages:
- Faster SELECT queries
Disadvantages:
- Slower INSERT/UPDATE operations
- Extra storage
Indexes should be used on frequently searched columns, not on frequently updated ones.
Microservices architecture breaks application into independent services.
Benefits:
- Independent deployment
- Scalability
- Fault isolation
Challenges:
- Network latency
- Data consistency
- Monitoring complexity
Used in large-scale distributed systems.
- Frontend: Lazy loading, memoization, CDN
- Backend: Caching, async processing, API optimization
- Database: Indexing, query optimization
- Infrastructure: Load balancing, horizontal scaling
Performance optimization is continuous and data-driven.
- Identify issue using monitoring/logs
- Analyze root cause
- Apply hotfix if critical
- Communicate with stakeholders
- Deploy fix
- Perform post-mortem analysis
- Implement preventive measures
This ensures system stability and continuous improvement.
Common challenges in automation testing include test script maintenance, handling dynamic elements, selecting appropriate test cases for automation, and dealing with different environments. These challenges can be addressed through regular code reviews, adopting good coding practices, using version control, and implementing robust test data management strategies. Regular updates to automation scripts to accommodate changes in the application are also essential.
Automation Testing
Yes, upon successfully completing the Online Automation Testing (Java Selenium) Course, you will receive a course completion certificate. This certificate can be a valuable addition to your professional portfolio and showcase your proficiency in automation testing.
Automation testing offers advantages such as faster execution, repeatability, reusability of test scripts, increased test coverage, early detection of defects, and the ability to run tests in parallel. It also reduces the need for human intervention in repetitive tasks.
Examples of popular automation testing tools include Selenium (for web applications), Appium (for mobile applications), JUnit and TestNG (for Java), and PyTest (for Python). These tools provide features like cross-browser testing, parallel test execution, and support for various programming languages.
Selenium is an open-source automation testing framework widely used for web applications. It provides a suite of tools for different testing needs. Selenium WebDriver allows interaction with web elements, while Selenium Grid facilitates parallel test execution across multiple browsers and platforms.
TestNG is a testing framework for Java, inspired by JUnit and NUnit. It supports parallel execution, test parameterization, grouping of test methods, and the generation of test reports. TestNG is often used in conjunction with Selenium for writing and managing test scripts.
The Page Object Model is a design pattern used in automation testing, particularly in Selenium. It involves creating a separate class for each web page or component, encapsulating the page’s elements and operations. This enhances code maintainability and reusability by keeping the page-specific code isolated.
Dynamic elements on a web page may change their attributes or state during runtime. Techniques to handle dynamic elements include using explicit waits (WebDriver Wait in Selenium), waiting for specific conditions, and using dynamic locators. XPath and CSS selectors can also be crafted to handle dynamic attributes.
Continuous Integration is a development practice where code changes are automatically built, tested, and integrated into a shared repository multiple times a day. Automation testing plays a crucial role in CI by executing test scripts automatically whenever code changes are pushed, ensuring early detection of defects.
BDD is a software development approach that encourages collaboration between developers, testers, and non-technical stakeholders. Tools like Cucumber and JBehave facilitate BDD in automation testing by allowing the creation of feature files written in a natural language format. These files can then be translated into executable test scripts.
Common challenges in automation testing include test script maintenance, handling dynamic elements, selecting appropriate test cases for automation, and dealing with different environments. These challenges can be addressed through regular code reviews, adopting good coding practices, using version control, and implementing robust test data management strategies. Regular updates to automation scripts to accommodate changes in the application are also essential.
REST API Testing
REST (Representational State Transfer) is an architectural style for designing networked applications. REST API testing involves verifying that the APIs adhere to REST principles, and it includes testing the functionality, security, performance, and reliability of the APIs.
RESTful APIs are designed to be stateless, scalable, and lightweight. They use standard HTTP methods (GET, POST, PUT, DELETE) for operations and often return data in JSON or XML format. Traditional web services, like SOAP, are more rigid in structure and use XML for data exchange.
The common HTTP methods are: 1) GET: Retrieve data
2)POST: Create a new resource
3)PUT: Update an existing resource
4)DELETE: Remove a resource
These methods align with CRUD operations (Create, Read, Update, Delete).
Authentication in REST API testing is often done using API keys, OAuth tokens, or other authentication mechanisms. Authorization is typically managed through roles and permissions associated with the user or client making the API request.
API endpoints are specific URLs or URIs that represent resources in a RESTful API. Each endpoint corresponds to a specific functionality or data entity. For example, /users might represent a collection of user resources, and /users/{id} might represent a specific user.
Postman is a popular API testing tool that allows testers and developers to create, share, test, and document APIs. It provides a user-friendly interface for making API requests, organizing them into collections, and writing test scripts for automation.
Postman supports various authentication methods, including API keys, OAuth, and basic authentication. In Postman, you can add authentication details in the request settings, allowing you to test secured APIs.
