Add Spring Boot Examples to Lab 3 (Generation and Refactoring)

[shawnewallace]

✅ Lab 3 Java/Spring Boot Version Complete

Created a separate Java version of Lab 3 following the successful Lab 2 pattern for focused, stack-specific learning.

Changes Summary

New File: docs/labs/lab-03-generation-and-refactoring-java.md

• Size: 1,053 lines (complete Spring Boot adaptation)
• Commit: 85fefc1

Updated Files:

• lab-03-generation-and-refactoring.md - Added cross-reference to Java version
• docs/labs/README.md - Updated Lab 3 section with both versions

Java/Spring Boot Content

Part 1: Generate REST API Endpoints (CRUD Operations)

Service Layer Methods:

• findAllTasks(TaskStatus status) with optional filtering
• findTaskById(UUID id) returning Optional
• updateTask(UUID id, UpdateTaskRequest request) with @transactional
• deleteTask(UUID id) with EntityNotFoundException

Controller Endpoints:

• GET /api/tasks with optional status query parameter
• GET /api/tasks/{id} returning 200 OK or 404 Not Found
• PUT /api/tasks/{id} with UpdateTaskRequest DTO
• DELETE /api/tasks/{id} returning 204 No Content

Spring Boot Patterns:

• @RestController with @RequestMapping("/api/tasks")
• @GetMapping, @PutMapping, @DeleteMapping annotations
• @PathVariable and @RequestParam for parameters
• ResponseEntity for flexible responses
• @ExceptionHandler for IllegalArgumentException
• @slf4j for structured logging

Testing:

• JUnit 5 unit tests for service layer with Mockito
• Integration testing patterns with @SpringBootTest

Part 2: Refactor Legacy Code

Before Issues:

• No Spring annotations
• Nested if statements (6+ levels)
• Thread.sleep() blocking operations
• Swallowed exceptions (empty catch blocks)
• No logging
• Magic numbers and poor naming
• String concatenation in loops
• Mixed concerns

After Improvements:

• @service with @slf4j annotations
• @requiredargsconstructor for constructor injection
• Guard clauses (early returns)
• Proper exception handling with logging
• ProcessingResult value object
• ProcessingType enum
• StringBuilder for efficiency
• Extracted methods: processSingleTask(), isTaskValid(), executeTaskProcessing()
• SLF4J structured logging with parameters

Expected Refactored Structure:

@Service
@Slf4j
@RequiredArgsConstructor
public class RefactoredTaskProcessor {
    private final TaskRepository taskRepository;
    private final TaskOutputWriter taskOutputWriter;
    
    public ProcessingResult processTaskBatch(List<TaskItem> tasks) {
        // Guard clauses
        // Process with proper error handling
        // Return comprehensive result
    }
}

Part 3: Object Calisthenics

Wrap Primitives:

• TaskId value object with @embeddable annotation
• Priority enum with validation
• TaskStatus enum
• JPA @EmbeddedId for value objects

First-Class Collections:

• TaskCollection wrapping List
• Immutable views with List.copyOf()
• Domain-specific operations (findById, filterByStatus)

No Abbreviations:

• Expanded: var t → Task task
• Expanded: var res → Optional<Task> result
• Expanded: int cnt → int itemCount

Tell, Don't Ask:

• Replace getters with behavior methods
• task.isCompleted() instead of checking status + completedAt

Part 4: Multi-File Refactoring

• Copilot Edits for consistent changes
• Working set management
• Review process for AI-generated changes
• Same concepts as .NET version

Extension Exercises

1. Pagination: Spring Data Pageable with PageRequest
2. Sorting: Sort.by() with multiple fields
3. Response Mapper: Dedicated TaskResponseMapper component

Design Decision: Separate Files

Continuing the Lab 2 pattern:

✅ Better Focus: Java developers see only Spring Boot patterns
✅ Manageable Size: 758 (.NET) vs 1,053 (Java) lines
✅ Clear Examples: Spring-specific annotations and patterns
✅ Easy Comparison: Cross-links for developers learning both stacks

Epic #16 Progress

With this completion: 6 of 15 issues complete (40%)

Next Steps

Continue with:

• Issue Add Modernization Scenarios to Capstone Lab (Lab 10) #27: Lab 10 (Capstone Build Agent) - Java scenarios
• Other remaining labs (Update Facilitator Guides for Bilingual (Dual-Stack) Delivery #18 Facilitator Guides, Create Modernization Agent (Mule → Spring Boot) #20-23 Custom Agents)

Lab 3 ready for Workshop 2.0 with both .NET and Java/Spring Boot support! 🎉