Spring Boot API: Insurance Quote Application

Build APIs That Work—Clearly, Confidently, and With Purpose

Spring Boot API: Insurance Quote Application will help you master Spring Boot, Java, and Test-Driven Development by building a real-world insurance quote application, guided by clear, practical steps and hands-on coding exercises.

Discover how to design robust APIs, implement microservices, and apply Agile best practices with user stories, Gherkin scenarios, and comprehensive testing strategies.

Whether you’re a beginner or refining your skills, this book empowers you to create scalable, maintainable software solutions for today’s enterprise environments

Gerry Byrne

Discover how to design robust APIs, implement microservices, and apply Agile best practices with user stories, Gherkin scenarios, and comprehensive testing strategies.

Whether you’re a beginner or refining your skills, this book empowers you to create scalable, maintainable software solutions for today’s enterprise environments

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About the Book

Looking for a Spring Boot API book that goes beyond boilerplate code? Spring Boot API: Insurance Quote Application is a hands‑on guide for developers who want to build real, production‑ready applications. Whether you’re new to Spring Boot or refining your Agile skills, this book walks you through the full development lifecycle—from user stories and Gherkin scenarios to Test‑Driven Development, layered architecture, microservices integration, and API testing with Postman, Swagger, and mocking frameworks.

Software architecture isn’t just about layers, endpoints, and data flow—it’s about people. Behind every controller is a user story. Behind every test case is a team striving to build with confidence. This book invites you to see Spring Boot development not just as a technical craft, but as a human one. Through clear diagrams, real‑world APIs, and thoroughly commented code, you’ll explore how thoughtful design can shape better software.

Inside, you will build three APIs in the form of microservices that power a dynamic insurance platform. You’ll explore:

Agile development with real‑life scenarios
Test‑Driven Development using JUnit
Testing with Mockito
Spring Boot layering: controllers, services, repositories, DTOs, and exceptions
JPA with H2 database, validation, and response entities
Pagination and dynamic search endpoints for user‑facing data
Deployment on a Tomcat server with practical configuration tips

With consistent terminology and clearly explained code examples, this book helps you connect the dots between backend architecture and real‑world impact. Each technical decision—every layer, test, and naming convention—isn’t just about code quality, it’s about making life easier for:

The developer who inherits your code
The learner trying to understand the flow
The user who relies on the application to solve a real problem

Take your Spring Boot skills to the next level and build APIs that truly work—with clarity, confidence, and purpose.

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About the Author

Gerry Byrne

Gerry Byrne is a Senior Technical Trainer at a Forbes 100 company, where he specializes in upskilling software engineers who build business critical applications. With a long career as a teacher, lecturer, and corporate trainer, Gerry brings a rare blend of academic rigor and real-world insight to his instruction.

He has delivered technical training across a wide spectrum of languages and frameworks, including Java, Spring, C#, Python, and JavaScript. His expertise in Spring Boot and API development is grounded in years of hands-on experience teaching modern enterprise technologies to engineers at all stages of their careers, from new graduates to those re-entering the workforce, to seasoned professionals.

Gerry’s approach to training emphasizes clarity, practical application, and a deep understanding of how software development fits into commercial environments. Whether introducing Test-Driven Development or guiding teams through the intricacies of RESTful API design, he equips learners with the tools they need to thrive in today’s fast-paced tech landscape.

Table of Contents

Spring Boot API: Electrical Items Insurance

What you will learn
On completing the learning, you will
Introduction - Spring Boot Electrical Items Insurance
1 AGILE USER STORIES
- What Is a User Story?
- Why Are User Stories Important?
- User Stories and Acceptance Criteria
- How to Write Effective User Stories
- User Stories in Agile Workflows
- Sprint Planning
- Continuous Collaboration
- TDD and BDD Integration
- Examples of User Stories in an Online Insurance System
- User Stories in Gherkin Format
- What is Gherkin?
- The GWT Structure
- Explaining Gherkin with an Insurance Company Example
- Scenario analysis
2 QUICK SPRING BOOT SETUP
- Creating a Simple Spring Boot Project
- What is pom.xml?
- Analysis of the pom.xml code sections
- Creating a Basic Controller
- Analysis of the HealthCheckController code
- Analysis of the DemoApplication code
- Creating a Basic Model
- Analysis of the DemoApplication code
- Analysis of the mapping code
- Creating a Basic Service
- Analysis of the mapping code
- Creating a Basic DTO
- What is a DTO?
- Analysis of the QuoteResponseDto?
- Analysis of the calculatequotevaluedto mapping?
- Summarizing our basic API
3 TEST-DRIVEN DEVELOPMENT
- JUnit 5 versus JUnit 4
- Creating a Maven Project
- pom.xml
- Product Type Factor Tests
- More Tests
- Product Value Factor Tests
- Calculate Quote Tests
- More robust testing
- Separation of Concerns
- Modularity
- Maintainability
- Testability
- Application of Separation of Concern in Java and Other Languages
- Separation of Concern for the business logic
- Separation of Concern for the tests
- Create a test suite
- Understanding the manifest and jar files
- Configure the project to build a jar file
- Maven configuration (command/script)
- Summary
4 SPRING BOOT API – INSURANCE QUOTE BACKEND
- Explanation of common layers
- User Stories
- Project setup
- Starter poms
- The Model Class
- Data Transfer Objects (DTO)
- The Repository Class
- The Service Class
- Create functionality
- Read functionality
- Update functionality
- Delete functionality
- Find record by its id functionality
- RestTemplate
- External Service Client
- The Exception Classes
- The Controller Class
- HTTP responses
- Handling HTTP Requests with Spring's Mapping Annotations
- Adding database functionality
- Configuring the database
- Server Port
- Database setup
- JPA & Hibernate Configuration
- H2 Console Access
- SQL Records
- The Application Class – the main method
- Test the endpoints
- CORS
- HTTP Client in IntelliJ IDEA Ultimate Edition
- Download Postman
- Testing the API with Postman
- The database table
- Derived Queries - (SQL Queries)
- Naming convention
- Supported Keywords
- Basic Derived Query
- Using GreaterThan
- Using LessThan
- Using And
- Using Or
- Using Between
- Using Like
- Using In
- Using OrderBy
- Optional
- Derived queries in the Repository layer
- Derived queries in the Service layer
- Derived queries in the Controller layer
- Why These Endpoints Belong in the Controller
- Test the SQL endpoints
- Quote Calculations as a service
5 PRODUCT DESCRIPTION MICROSERVICE
- Creating a Maven Project for the Microservice
- Project setup
- The database table
- Testing the API with Postman
6 CUSTOMER MICROSERVICE
- Creating a Maven Project for the Microservice
- Project setup
- Database Records
- The database table
- Testing the API with Postman
7 TESTING THE MICROSERVICES INTEGRATION
8 PAGINATION AND DYNAMIC SEARCHING
- Pagination with sorting
- Dynamic searching
9 VALIDATION
- Layered approach for where and what to validate
- Global Exception handler
- Entity Field Validation
- Controller Method Validation
- Query Parameter Validation
10 MOCKING
- Introduction to mocking
- Why We Use Mocking
- Mockito – A Popular Mocking Framework
11 LOGGING
- Introduction to logging with SLF4J
- Controller Layer Logging
- Testing the API with Postman
- Testing the API controllers with Postman
- Service Layer Logging
- Testing the API service methods with Postman
- Repository Layer Logging
- Exceptions Layer Logging
12 SWAGGER
- Introduction to Swagger
- What is Swagger?
- The Springdoc OpenAPI Dependency
- Compatibility with Spring Boot Versions
- Swagger Integration with our application
- Generated Endpoints and API Documentation
- Documenting our InsuredItem endpoints
- Testing and Interactive Features
- Schema Generation and Validation Documentation
- Advanced Endpoint Documentation
13 RESTTEMPLATE AND WEBCLIENT
- RestTemplate - A Classic Approach
- WebClient - A Modern, Reactive Solution
- Analysis of the WebClientConfig code
- Analysis of the ProductClientService code
- Analysis of the CustomerController getProductTypes() code
- Analysis of the ProductClientService code
- Analysis of the CustomerController getProductDescriptionByType() code
- Separate Configuration Class Approach (CustomerMicroservice)
- Main Application Class Approach (InsuredItem Microservice)
14 GLOSSARY OF TERMS
- Spring API terms
- WebClient terms

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