# spring-security-demo

Companion code for the Spring Security series on [ankurm.com](https://ankurm.com). Each
directory is a self-contained Maven project for one article, with its own `pom.xml`, its own
numbered documentation chapters, and its own captured output under `docs/output/` — regenerated
by that module's `scripts/run-all.sh`, never typed by hand.

| Module | Article | What it demonstrates |
|---|---|---|
| [`context-propagation/`](context-propagation/README.md) | [Spring Security Context Propagation: The Complete Guide](https://ankurm.com/spring-security-context-propagation-complete-guide/) | Whether a `SecurityContext` survives `@Async`, executors, virtual threads, `StructuredTaskScope`, Reactor, schedulers and the servlet filter chain |
| [`method-security/`](method-security/README.md) | [Method Security in Spring Security 7: `@PreAuthorize`, `@PostAuthorize` and the Proxy Traps](https://ankurm.com/spring-security-7-method-security-proxy-traps/) | What the method-security annotations do, the full SpEL surface, and the cases where the check silently does not run |
| [`filter-chain/`](filter-chain/README.md) | [The Spring Security Filter Chain Explained](https://ankurm.com/spring-security-filter-chain-explained/) | Every filter in the default chain and its order number, where a custom filter actually lands, and how to read the TRACE log |
| [`cors-csrf/`](cors-csrf/README.md) | [CORS, CSRF and SameSite in Spring Boot 4](https://ankurm.com/spring-boot-4-cors-csrf-samesite/) | Why MVC-layer CORS does not fix a security-layer preflight rejection, what `csrf.spa()` assigns, and the cookie a browser silently refuses to store |
| [`service-to-service/`](service-to-service/README.md) | [Securing Spring Boot Microservices: Token Relay, Service-to-Service JWT and mTLS](https://ankurm.com/spring-boot-microservices-token-relay-mtls/) | Whose identity arrives at the last service under relay, client credentials and token exchange — and what a resource server does not check by default |

They are related more closely than they look. `filter-chain` is about how an `Authentication`
gets into `SecurityContextHolder` in the first place and in what order; `context-propagation` is
about whether it survives leaving the request thread; `method-security` reads it back on whatever
thread it ends up on. An `@Async` method carrying `@PreAuthorize` fails with
`AuthenticationCredentialsNotFoundException` for reasons that belong to the second module, not
the third — and a custom authentication filter that never populated the context in the first
place fails the same way, for reasons that belong to the first.

`service-to-service` is the same question one process further out: `cors-csrf` and
`context-propagation` ask whether an identity survives a thread or a browser boundary, and this
one asks whether it survives an HTTP boundary — and what the service on the far side bothers to
verify about it. Its `/edge/relay-async` endpoint fails for exactly the reason
`context-propagation` documents.

`cors-csrf` is where those order numbers stop being trivia. `CorsFilter` at 1000 and `CsrfFilter`
at 1100 both sit far above `AuthorizationFilter` at 4200, and almost every confusing symptom in
that module is a consequence of one of those three positions — including a 403 that arrives as a
401 because the container re-dispatched the request to `/error` and the chain ran a second time.

## Common ground

All modules target the same verified stack: **JDK 25** (Temurin 25.0.4.1+1),
**Spring Framework 7.0.9**, **Spring Security 7.1.1** — the versions Spring Boot **4.1.1**
manages. Versions were taken from `maven-metadata.xml` on Maven Central rather than from
release announcements.

`context-propagation` additionally needs `--enable-preview`, because `StructuredTaskScope` is
still a preview API on JDK 25. `method-security` does not. `filter-chain`, `cors-csrf` and
`service-to-service` are real servlet applications: they inherit `spring-boot-starter-parent`
and run on Tomcat, because the things they demonstrate only exist inside a servlet container.
`service-to-service` runs five of them at once, and is the only module that also pulls in
Spring Cloud — a separate release train, built against Boot 4.0.8 rather than 4.1.1.

## Running a module

```bash
cd cors-csrf                # or context-propagation, method-security, filter-chain, service-to-service
./scripts/run-all.sh        # every demo plus the test suite, regenerating docs/output/
mvn test                    # just the assertions
```

`filter-chain` and `cors-csrf` also have `./scripts/run.sh <profile>` and `./scripts/stop.sh`,
because their scenarios are a running web application rather than a `main()` method.
`cors-csrf` adds `./scripts/preflight.sh`, which sends one CORS preflight and prints the headers
that decide the outcome.

## License

MIT — see [LICENSE](LICENSE).