Initialize Spring Boot backend with JWT auth

src/main/java/com/openisle/service/JwtService.java

@@ -0,0 +1,45 @@
+package com.openisle.service;
+
+import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Jwts;
+import io.jsonwebtoken.SignatureAlgorithm;
+import io.jsonwebtoken.security.Keys;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+import java.security.Key;
+import java.util.Date;
+
+@Service
+public class JwtService {
+
+    @Value("${app.jwt.secret}")
+    private String secret;
+
+    @Value("${app.jwt.expiration}")
+    private long expiration;
+
+    private Key getSigningKey() {
+        return Keys.hmacShaKeyFor(secret.getBytes());
+    }
+
+    public String generateToken(String subject) {
+        Date now = new Date();
+        Date expiryDate = new Date(now.getTime() + expiration);
+        return Jwts.builder()
+                .setSubject(subject)
+                .setIssuedAt(now)
+                .setExpiration(expiryDate)
+                .signWith(getSigningKey(), SignatureAlgorithm.HS256)
+                .compact();
+    }
+
+    public String validateAndGetSubject(String token) {
+        Claims claims = Jwts.parserBuilder()
+                .setSigningKey(getSigningKey())
+                .build()
+                .parseClaimsJws(token)
+                .getBody();
+        return claims.getSubject();
+    }
+}