Add enum-based courses and configuration properties example

Author: gabriele.sisinna

README.md

@@ -34,6 +34,8 @@ Full repo learning notes are in [docs/README.md](./docs/README.md).
 - JPA + H2 persistence
 - basic authentication with Spring Security
 - unit, repository, and integration tests
+- enums
+- `@ConfigurationProperties`
 
 ## Start here
 
@@ -48,7 +50,8 @@ Read these files in order:
 7. `src/main/java/com/example/demo/spring/service/StudentService.java`
 8. `src/main/java/com/example/demo/spring/persistence/service/CourseService.java`
 9. `src/main/java/com/example/demo/spring/persistence/controller/CourseController.java`
-10. `src/test/java/com/example/demo/spring/persistence/controller/CourseControllerIntegrationTest.java`
+10. `src/main/java/com/example/demo/spring/config/AppLearningProperties.java`
+11. `src/test/java/com/example/demo/spring/persistence/controller/CourseControllerIntegrationTest.java`
 
 ## Package guide
 
@@ -76,6 +79,8 @@ Read these files in order:
   - request and response models
 - `com.example.demo.spring.persistence`
   - validation, JPA, H2, and security examples
+- `com.example.demo.spring.config`
+  - OpenAPI config and typed configuration properties
 
 ## Run the app
 
@@ -142,19 +147,44 @@ Get secured courses with basic auth:
 curl -u student:password http://localhost:8080/api/courses
 ```
 
+Show typed configuration properties:
+
+```bash
+curl http://localhost:8080/api/learning-info
+```
+
 Create a secured database-backed course:
 
 ```bash
 curl -u student:password -X POST http://localhost:8080/api/courses \
   -H "Content-Type: application/json" \
   -d '{
     "title": "Spring Data JPA",
-    "level": "intermediate",
+    "level": "INTERMEDIATE",
     "durationInHours": 7,
     "published": true
   }'
 ```
 
+Update a course:
+
+```bash
+curl -u student:password -X PUT http://localhost:8080/api/courses/1 \
+  -H "Content-Type: application/json" \
+  -d '{
+    "title": "Updated Java Generics",
+    "level": "ADVANCED",
+    "durationInHours": 10,
+    "published": false
+  }'
+```
+
+Delete a course:
+
+```bash
+curl -u student:password -X DELETE http://localhost:8080/api/courses/2
+```
+
 ## Swagger and OpenAPI
 
 After starting the app with `./gradlew bootRun`, open:
@@ -193,7 +223,7 @@ Different test layers in this repo:
 
 - unit tests: small classes without Spring, such as `StudentTest` and `CourseServiceTest`
 - repository tests: JPA + H2 with a Spring Boot integration test, such as `CourseRepositoryTest`
-- integration tests: full Spring Boot + MockMvc, such as `StudentControllerTest` and `CourseControllerIntegrationTest`
+- integration tests: full Spring Boot + MockMvc, such as `StudentControllerTest`, `CourseControllerIntegrationTest`, and `LearningInfoControllerTest`
 
 ## GitHub CI
 
@@ -226,9 +256,11 @@ It runs on every push and pull request, sets up Java 17, and executes:
 - Inheritance: `Person`, `LearningStudent`
 - Generics: `Box<T>`
 - Streams: `StudentAnalytics`
+- Enums: `CourseLevel`
 - Exceptions: `InvalidScoreException`, `StudentNotFoundException`
 - Annotations: `@LearningExample`, `@Service`, `@RestController`, `@RestControllerAdvice`, `@Entity`, `@Valid`
 - Dependency injection: `StudentController` gets `StudentService`, `StudentService` gets `InMemoryStudentRepository`
 - Validation: `CreateCourseRequest`
 - Persistence: `CourseEntity`, `CourseRepository`, H2
 - Security: HTTP basic auth for `/api/courses/**` with user `student` / `password`
+- Typed configuration: `AppLearningProperties` bound from `application.yml`

docs/java-basics.md

@@ -159,6 +159,18 @@ Key idea:
 - generics let you write reusable classes while keeping type safety
 - `Box<String>` and `Box<Integer>` use the same class with different types
 
+## Enums
+
+Example:
+
+- `spring/persistence/model/CourseLevel.java`
+
+Key idea:
+
+- enums model a fixed set of allowed values
+- they are safer than raw strings
+- they work well for states, levels, and categories
+
 ## Streams and lambdas
 
 Example:

docs/spring-boot.md

@@ -107,6 +107,19 @@ Flow:
 3. invalid input triggers an exception
 4. `ApiExceptionHandler` turns it into a clean error response
 
+## Configuration properties
+
+Main files:
+
+- `AppLearningProperties`
+- `LearningInfoController`
+
+Key idea:
+
+- `@ConfigurationProperties` maps structured YAML into a typed Java object
+- this is cleaner than scattering config lookups through the code
+- the `/api/learning-info` endpoint makes the bound values visible at runtime
+
 ## Exception handling
 
 Main example:
@@ -134,6 +147,7 @@ Key ideas:
 
 - `@Entity` maps a class to a database table
 - a `JpaRepository` gives CRUD operations
+- `CourseLevel` enum keeps the `level` field restricted to valid values
 - H2 provides an in-memory database for easy learning
 - `data.sql` seeds example rows at startup