Claude
ba709737de
Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5 Co-Authored-By: Claude Sonnet 5.5 <[email protected]> Claude-Session: https://claude.ai/code/session_01HhW8LD8r3EigoBaCGrQZx5
52 lines
2.2 KiB
Markdown
52 lines
2.2 KiB
Markdown
# project-structure
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Companion project for the article **[Spring Boot Project Structure: Package-by-Layer vs Package-by-Feature](https://ankurm.com/spring-boot-project-structure/)** on **[ankurm.com](https://ankurm.com)**.
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One small library application (books, plus loans in the feature layout) written twice, with the same
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HTTP API, so the only difference between the two is where the files live. Every console block quoted in
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the article came out of `output/`, written by the test suite, so a claim that stops being true turns the
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build red.
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There is deliberately **no `docs/` folder**: the deeper material lives in collapsible sections inside the
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article itself.
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## Versions
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| Spring Boot | 4.1.1 |
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| Spring Framework | 7.0.9 |
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| JDK | 21 (OpenJDK 21.0.12) |
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| Maven | 3.9 |
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The module was compiled and run on JDK 21 only; it has not been run on JDK 25.
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## Quickstart
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```bash
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mvn test # runs everything and rewrites output/01-04
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./scripts/run-all.sh # same, then lists output/
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mvn spring-boot:run # starts the recommended (by-feature) layout on :8080
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```
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## Source layout
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| Package | What it is |
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| `bylayer/` | package-by-layer: `controller/`, `service/`, `repository/`, `model/`, `dto/`, `exception/` |
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| `byfeature/book/` | the book feature: everything package-private except `BookCatalog`, the feature's public API |
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| `byfeature/loan/` | the loan feature: uses books only through `BookCatalog` |
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| `byfeature/shared/` | cross-cutting: `ApiException` and the one `@RestControllerAdvice` |
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Both applications have their own `@SpringBootApplication` (`ByLayerApp`, `ByFeatureApp`), and each scans
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only its own package, so the two never see each other's beans.
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## Captured output
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| File | What it shows |
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| `01-package-trees.txt` | the real source tree of both layouts (9 files vs 15 files) |
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| `02-public-surface.txt` | every top-level type and whether it is `public`: 9 of 9 by layer, 3 of 15 by feature |
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| `03-compiler-boundary.txt` | the same one-line shortcut (`new BookRepository()` from another package): compiles by layer, rejected by `javac` by feature |
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| `04-same-api-both-layouts.txt` | five identical requests against both layouts, plus the loan feature's three requests |
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