Spring Security 7.1 JWT authentication on Spring Boot 4.1

Runnable companion for https://ankurm.com/spring-security-7-1-jwt-authentication-guide/

- login -> token issue -> OncePerRequestFilter -> SecurityContext, end to end
- HS256 and RS256 variants (RS256 publishes a real JWKS endpoint)
- the same API secured by the built-in oauth2ResourceServer().jwt(), for comparison
- 11 documentation chapters under docs/, interlinked with the code
- docs/output/ is real captured output, regenerated by scripts/run-all.sh
- 13 passing tests pinning the 401-vs-403 contract and the CSRF failure

Verified against Spring Boot 4.1.1, Spring Security 7.1.1, JDK 25.0.4.1.

scripts/expiry-demo.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# Requires: --spring.profiles.active=hs256,shortlived  (2-second access tokens)
+set -u
+BASE="${1:-http://localhost:8080}"
+show() {
+  local out; out=$(curl -sS -D /tmp/.h -o /tmp/.b -w '%{http_code}' "$@")
+  printf 'HTTP %s\n' "$out"
+  grep -iE '^www-authenticate:' /tmp/.h | sed 's/\r$//'
+  [ -s /tmp/.b ] && { python3 -m json.tool < /tmp/.b 2>/dev/null | head -6 || cat /tmp/.b; }
+  echo
+}
+hr(){ printf '\n%s\n' "--------------------------------------------------------------------------"; }
+
+echo "=========================================================================="
+echo " jwt-auth-demo - token expiry and the 60-second clock skew"
+echo " profiles: hs256,shortlived   (access-token-ttl = 2s)"
+echo "=========================================================================="
+
+TOK=$(curl -sS -X POST "$BASE/api/auth/login" -H 'Content-Type: application/json' \
+      -d '{"username":"alice","password":"alice-password"}' | python3 -c 'import json,sys;print(json.load(sys.stdin)["accessToken"])')
+
+hr; echo "# T+0s  - fresh token"; echo; show "$BASE/api/me" -H "Authorization: Bearer $TOK"
+
+hr; echo "# T+5s  - exp has passed, but JwtTimestampValidator allows 60s of clock skew"
+echo "#         by default, so the token is STILL accepted. This surprises people"
+echo "#         who write a test that sleeps past exp and expects a 401."
+echo; sleep 5; show "$BASE/api/me" -H "Authorization: Bearer $TOK"
+
+hr; echo "# T+65s - past exp + the 60s skew window. Now it is refused."
+echo; sleep 60; show "$BASE/api/me" -H "Authorization: Bearer $TOK"
+
+hr; echo "# end"