Learn Spring Boot 4 by Examining 7+ Practical Applications

Explore how Maven manages a Spring project, using pom.xml, dependencies, and the spring-boot-starter-web dependency. Learn Maven conventions over configuration and how the project object model coordinates build and packaging.

Explore the basics of a Spring Boot application, including beans, dependency injection, and key annotations such as @Bean, @SpringBootApplication, and @Controller, plus REST controllers and Maven builds.

Complete the first self assignment, explore the BeansController and its spring bean, and verify the @GetMapping('/beans') returns an array of strings after startup.

Run the second Spring Boot application on port 8002, serving static pages and a dynamic greeting via Thymeleaf templates, with a GreetingController parsing name and age.

Engage in a hands-on challenge by modifying a spring boot 4 app: return templates/greeting.html, switch the form to post, and compute age from birth date for under-18 templates.

Run the Spring Boot 4 application to see a signup form validated with not blank, not null, and digits checks, plus custom date of birth validation and a signup-completed page.

Apply bean validation to enforce a valid email for the username using the correct Bean Validation 2.0 and Hibernate Validator annotations, and resolve the BigDecimal error while reviewing DayTimeFormat guidance.

Map Java objects to relational database entities using JPA, compare object graphs to table-based data, and map POJOs with @Entity for ORM, including foreign keys and auto primary key generation.

Explore REST concepts, resources and URIs, HTTP verbs, and how to map requests to controller methods in Spring Boot with annotations, curl testing, and HTTP status code handling via HandlerAdvice.

Explore the REST architectural style for designing web APIs, using stateless, resource-based requests with standard HTTP verbs to create, read, update, and delete resources.

Run the spring boot application and use curl to query courses and enrollments, post enrollments, and observe responses such as 201 created, 404 not found, and 400 bad request.

Replace RestTemplate with RestClient in a Spring Boot 4 app, using a RestClient bean to fetch courses and manage enrollments via GET, POST, and DELETE calls.

Recap the section's practical work: rest calls with RestTemplate and RestClient, JSON translation with Jackson, and using Spring profiles to toggle beans and handle put request with a 400 status.

Use MockMVC to run controller tests without starting a web server, speeding up tests by mocking the web environment and using MockMVC assertions for fast, reliable verification.

Explore unit, web mvc tests, and integration tests for a Spring Boot enrollment controller, validating dates, mocking repositories, and verifying 201, 400, or 500 responses.

Cover the code with automatic tests, using unit tests with mocks via Mockito and validating mocked calls; explore integration tests with MockMVC and WebMVC to test a post endpoint.