Add hibernate-demo: get() vs load(), merge() vs refresh(), inserting objects (Hibernate 7.4.1.Final + Spring Boot 4.1.0)

2026-08-26 17:26:04 +00:00
commit 5533c6c8fe
24 changed files with 1653 additions and 0 deletions
--- a/README.md
+++ b/README.md
@@ -0,0 +1,99 @@
+# hibernate-demo
+
+Companion repository for three ankurm.com posts on Hibernate 7's persistence-context APIs:
+`get()` vs `load()`/`getReference()`, `merge()` vs `refresh()`, and inserting objects
+efficiently. Every claim in those posts that comes from this repo traces to a script here and a
+captured transcript in `docs/output/` — nothing is asserted that wasn't actually run.
+
+## Versions
+
+| Component | Version |
+|---|---|
+| Hibernate ORM | `7.4.1.Final` (GA 2026-06-09) |
+| Spring Boot | `4.1.0` (GA 2026-06-10) |
+| Java | `25` (LTS) |
+| H2 | in-memory, managed by Spring Boot |
+
+See [`docs/00-versions.md`](docs/00-versions.md) for how these were verified and a trap worth
+knowing about if you bump the Spring Boot version.
+
+## Quickstart
+
+```bash
+git clone https://ankurm.com/git.app/asmhatre/hibernate-demo.git
+cd hibernate-demo
+./scripts/run.sh getvsload
+```
+
+Requires JDK 25 and a network connection the first time (Maven needs to fetch plugins online
+before `-o` offline mode works for subsequent runs).
+
+## Profiles
+
+Each profile is a `CommandLineRunner` against an in-memory H2 database. There is no web server —
+every run starts, executes its scenario, prints the result, and exits.
+
+| Profile | Runs | Chapter |
+|---|---|---|
+| `getvsload` | `session.get()` vs `session.getReference()`, proxies, `LazyInitializationException` | [docs/01-get-vs-load.md](docs/01-get-vs-load.md) |
+| `mergerefresh` | `merge()` vs `refresh()` against a `@Version`-ed entity | [docs/02-merge-vs-refresh.md](docs/02-merge-vs-refresh.md) |
+| `insert-identity` | Batch insert attempt with `GenerationType.IDENTITY` | [docs/03-inserting-objects.md](docs/03-inserting-objects.md) |
+| `insert-sequence` | The same insert, with `GenerationType.SEQUENCE` | [docs/03-inserting-objects.md](docs/03-inserting-objects.md) |
+
+```bash
+./scripts/run.sh getvsload
+./scripts/run.sh mergerefresh
+./scripts/run.sh insert-identity
+./scripts/run.sh insert-sequence
+```
+
+## Regenerating captured output
+
+```bash
+./scripts/run-all.sh
+```
+
+Regenerates every file in `docs/output/` from a real run. `scripts/clean_output.py` strips JVM
+noise and a harmless duplicate SQL echo line so the committed transcripts stay readable —
+nothing else is edited by hand.
+
+## Documentation index
+
+| Chapter | Covers |
+|---|---|
+| [00 — Versions](docs/00-versions.md) | Verified version pins, and the Spring Boot patch that silently changes which Hibernate patch you get |
+| [01 — get() vs load()](docs/01-get-vs-load.md) | Proxy deferral, `LazyInitializationException`, proxy identity vs `equals()` |
+| [02 — merge() vs refresh()](docs/02-merge-vs-refresh.md) | Optimistic locking, which method fails loudly vs silently |
+| [03 — Inserting objects](docs/03-inserting-objects.md) | `IDENTITY` vs `SEQUENCE` and JDBC batching, with `hibernate.generate_statistics` as evidence |
+
+## Captured output index
+
+| File | Scenario |
+|---|---|
+| [docs/output/get-vs-load.txt](docs/output/get-vs-load.txt) | `getvsload` |
+| [docs/output/merge-vs-refresh.txt](docs/output/merge-vs-refresh.txt) | `mergerefresh` |
+| [docs/output/insert-identity.txt](docs/output/insert-identity.txt) | `insert-identity` |
+| [docs/output/insert-sequence.txt](docs/output/insert-sequence.txt) | `insert-sequence` |
+
+## Layout
+
+```
+hibernate-demo/
+├── pom.xml
+├── LICENSE
+├── scripts/
+│   ├── run.sh              start one profile, run it, exit
+│   ├── run-all.sh          regenerate every docs/output/ file
+│   └── clean_output.py     strip JVM noise + a duplicate SQL echo line from a raw capture
+├── src/main/java/com/ankurm/hibernatedemo/
+│   ├── HibernateDemoApplication.java
+│   ├── model/               Book, WidgetIdentity, WidgetSequence
+│   └── scenario/            one CommandLineRunner per profile
+└── docs/
+    ├── 00-versions.md .. 03-inserting-objects.md
+    └── output/*.txt         captured, unedited console transcripts
+```
+
+## License
+
+MIT — see [LICENSE](LICENSE).