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spring-and-spring-boot

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Lab solutions for Spring and Spring Boot course

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Comprehensive hands-on exercises for learning Spring Boot fundamentals, from basic web applications to database persistence patterns.

## Prerequisites

- **Java 21** (standardized across all projects)
- **Spring Boot 4.1.0** (current version, based on Spring Framework 7)
- **Gradle 9.6.1** (provided by the wrapper)
- IDE with Spring Boot support (IntelliJ IDEA, Spring Tool Suite, or VS Code)

### Before the First Day (Student Checklist)

1. **Install JDK 21** (any distribution — Temurin, Zulu, Oracle, SDKMAN all work)
2. **Install an IDE** with Spring support (IntelliJ IDEA recommended; Community Edition is fine)
3. **Optional — Docker Desktop**: needed only for the PostgreSQL/Testcontainers exercise; everything else uses in-memory H2
4. **Optional — OpenAI API key**: needed for the text-to-speech bonus and the Spring AI lab. Create one at platform.openai.com *before class* (account setup and billing take a few minutes) and put it in an `OPENAI_API_KEY` environment variable. Everything builds and runs without it; the AI exercises simply skip
5. **Optional — OpenRouter API key**: needed for the "one key, hundreds of models" bonus. Create one at openrouter.ai (no billing required — the demo uses free models) and put it in an `OPENROUTER_API_KEY` environment variable
6. **Network note**: several labs call public APIs (jsonplaceholder.typicode.com, api.chucknorris.io, ll.thespacedevs.com, api.openai.com, openrouter.ai). If you're on a corporate network, confirm those are reachable or expect some tests to skip/fail

## Two-Day Course Agenda

- **Day 1 — Web and REST fundamentals** (labs.md, Labs 1–6): creating a project, controllers and Thymeleaf, REST controllers with `RestTestClient`, consuming APIs with `RestClient`, HTTP Interfaces, configuration with `@Value`
- **Day 2 — Data access and beyond** (labs.md, Labs 7–11): `JdbcTemplate`, `JdbcClient`, JPA and Spring Data JPA, profiles, AOP (optional), plus a taste of Spring AI (Lab 12) if time permits
- **Optional self-study** (advanced-labs.md): the complete enterprise `shopping` application — validation, DTOs, RFC 7807 error handling, transactions, and comprehensive testing

> Bean Validation, global exception handling, and Spring Security are covered in the slides; hands-on practice for the first two lives in the advanced labs, and security is deliberately pointers-only — it deserves its own course.

## Lab Materials

### 📚 **labs.md** - Comprehensive Basic Labs
Foundation labs covering Spring Boot fundamentals from web development to database persistence.

### 🚀 **advanced-labs.md** - Enterprise Development Labs  
Advanced labs building a complete shopping application with enterprise patterns. **Updated to match the final implementation exactly** - students can copy from the solution when needed:
- Progressive entity design with JPA validation and Lombok
- Spring Data repositories with custom queries and indexes
- REST API development with modern DTOs and full CRUD operations
- Global exception handling with RFC 7807 ProblemDetail
- Transaction management and comprehensive testing strategies
- YAML configuration with profile separation using `---`

## Project Structure

This repository contains five independent Spring Boot projects that demonstrate different aspects of the framework:

### 📁 **demo** - Basic Spring Boot Web Application
- **Package**: `com.kousenit.demo`
- **Purpose**: Introduction to Spring Boot web development
- **Features**:
  - Thymeleaf templating
  - REST controllers with JSON responses
  - Unit and integration testing
  - Basic web forms and static content

### 📁 **restclient** - External API Integration
- **Package**: `com.kousenit.restclient`
- **Purpose**: Consuming external REST APIs
- **Features**:
  - Modern `RestClient` for synchronous calls
  - HTTP Interfaces for declarative clients
  - JSON Placeholder API integration (no API keys required)
  - Launch Library API for space data
  - OpenAI text-to-speech: a POST with a binary (mp3) response, streamed to a file
  - OpenRouter chat: one API key, hundreds of models; defaults to the free-model router
  - Comprehensive error handling

### 📁 **persistence** - Database Access Patterns
- **Package**: `com.kousenit.persistence`
- **Purpose**: Various approaches to data persistence
- **Features**:
  - Modern `JdbcClient` (Spring Boot 3.2+)
  - Traditional `JdbcTemplate`
  - JPA with Hibernate
  - Spring Data JPA repositories
  - H2 in-memory database

### 📁 **shopping** - Enterprise Shopping Application
- **Package**: `com.kousenit.shopping`
- **Purpose**: Complete enterprise application demonstrating advanced patterns
- **Features**:
  - JPA entities with comprehensive validation and Lombok
  - Database indexes for performance optimization
  - Spring Data JPA with custom queries and sophisticated repository patterns
  - Service layer with transaction management and business logic
  - REST API with modern DTOs and full CRUD operations
  - Global exception handling with RFC 7807 ProblemDetail responses
  - YAML configuration with test profile isolation
  - Sample data initialization with profile-aware CommandLineRunner
  - Comprehensive test suite with modern @MockitoBean annotations
  - Production-ready logging and monitoring endpoints

### 📁 **springai** - Spring AI Demo
- **Package**: `com.kousenit.springai`
- **Purpose**: Calling large language models with Spring AI 2.0
- **Features**:
  - `ChatClient` fluent API with the OpenAI starter
  - Structured output mapped onto Java records
  - Tests that skip themselves when `OPENAI_API_KEY` is not set

## Quick Start

### Build All Projects
```bash
# From the root directory
./gradlew build

# Or build individual projects
cd demo && ./gradlew build
cd restclient && ./gradlew build
cd persistence && ./gradlew build
cd shopping && ./gradlew build
cd springai && ./gradlew build
```

### Run Applications
```bash
# Demo application (port 8080)
cd demo && ./gradlew bootRun

# REST client examples
cd restclient && ./gradlew bootRun

# Persistence examples with H2 console
cd persistence && ./gradlew bootRun

# Shopping application (port 8080)
cd shopping && ./gradlew bootRun
```

### Run Tests
```bash
# All tests
./gradlew test

# Specific project tests
cd demo && ./gradlew test
cd restclient && ./gradlew test
cd persistence && ./gradlew test
cd shopping && ./gradlew test
```

## Key Learning Topics

### Modern Spring Boot Features
- **Spring Boot 4.1.0** with Java 21 features
- **Records** for immutable data classes and DTOs
- **Text blocks** for readable SQL and JSON
- **RestClient** as the modern replacement for RestTemplate
- **RestTestClient** (Spring Framework 7) for fluent integration testing
- **JdbcClient** as the modern alternative to JdbcTemplate
- **@MockitoBean** replacing deprecated @MockBean
- **Lombok** for reducing boilerplate with proper IDE integration
- **YAML configuration** with `---` profile separation
- **RFC 7807 ProblemDetail** for standardized error responses

### Web Development
- RESTful web services with `@RestController`
- Server-side rendering with Thymeleaf
- Static content and form handling
- HTTP client integration patterns

### Data Access
- **Modern JDBC**: JdbcClient and JdbcTemplate patterns
- **JPA Entity Mapping**: Annotations and relationship management
- **Spring Data JPA**: Repository pattern with automatic query generation
- **Database Configuration**: Multi-environment setup with profiles
- **Connection Management**: H2 for development, PostgreSQL for production

### Configuration Management
- **Property Injection**: `@Value` annotation for external configuration
- **Profile-Specific Properties**: `application-{profile}.yml` files
- **Environment Variables**: Secure configuration for production
- **Feature Toggles**: Profile-based conditional bean creation

### Testing
- **Unit Testing**: JUnit 5 with comprehensive assertions and modern patterns
- **Integration Testing**: `@SpringBootTest` with profile activation and test isolation
- **Web Layer Testing**: `@WebMvcTest` with MockMVC for REST API testing
- **Service Layer Testing**: `@MockitoBean` for dependency mocking
- **Entity Validation Testing**: Bean validation with constraint violation testing
- **Database Testing**: Repository testing with `@DataJpaTest`
- **Profile Testing**: `@ActiveProfiles` for environment-specific tests

## API Integrations

### JSON Placeholder (No API Key Required)
- **Users API**: Complex nested JSON structures with address and company data
- **Posts API**: Complete CRUD operations (GET, POST, DELETE)
- **Configuration**: Externalized URLs and timeouts with `@Value` annotation
- **Demonstrates**: Modern record classes, full HTTP method support, robust error handling

### Launch Library API
- **Space Expeditions**: Active expedition and astronaut assignment data
- **Demonstrates**: RestClient usage, nested JSON mapping, stream processing

### OpenAI (springai project; API key required)
- **Chat and structured output**: `ChatClient` demos in the `springai` project
- **Configuration**: Reads the `OPENAI_API_KEY` environment variable; builds cleanly without it

### OpenRouter (restclient project; API key required)
- **Chat completions**: hand-rolled `RestClient` + records against OpenRouter's OpenAI-compatible API — one key covers hundreds of models
- **Free-model router**: defaults to `openrouter/free` (configurable via `openrouter.model`), which picks a currently available free model and reports which one answered
- **Configuration**: Reads the `OPENROUTER_API_KEY` environment variable; tests skip without it

## Development Environment

### Recommended IDEs
- **IntelliJ IDEA Ultimate** - Full Spring Boot support
- **Spring Tool Suite** - Eclipse-based with Spring tools
- **VS Code** - With Spring Boot extensions

### Database Access

**Development Profile (default):**
- **H2 Console**: http://localhost:8080/h2-console
- **JDBC URL**: `jdbc:h2:mem:shopping` (or project-specific name)
- **Username**: `sa`
- **Password**: (empty)

**Profile Switching:**
```bash
# Run with different profiles
./gradlew bootRun --args='--spring.profiles.active=dev'    # H2 (default)
./gradlew bootRun --args='--spring.profiles.active=test'   # H2 optimized for testing
./gradlew bootRun --args='--spring.profiles.active=prod'   # PostgreSQL via Testcontainers

# Shopping application with debug logging
cd shopping && ./gradlew bootRun --args='--spring.profiles.active=dev'
```

**Shopping Application Endpoints:**
- **H2 Console**: http://localhost:8080/h2-console
- **Health Check**: http://localhost:8080/actuator/health
- **API Documentation**: http://localhost:8080/api/v1/products

### Optional Requirements

**Docker Desktop (for advanced testing):**
- Required for PostgreSQL Testcontainers integration
- Production profile tests will be skipped if Docker is unavailable
- All core functionality works without Docker using H2 database

## Modern Java Features Used

- **Records** - Immutable data classes for JSON mapping
- **Text Blocks** - Readable multi-line SQL queries
- **Pattern Matching** - Enhanced switch expressions
- **Local Variable Type Inference** - `var` keyword usage
- **Optional** - Null-safe API responses

## Contributing

This project follows modern Spring Boot best practices:
- Package structure: `com.kousenit.*`
- Java 21 features throughout
- Comprehensive test coverage
- Modern dependency management
- Clean separation of concerns

## License

See [LICENSE](LICENSE) file for details.