Created token validator

src/identity/controller/Validator.java

+package identity.controller;
+
+import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Jwts;
+import io.jsonwebtoken.SignatureAlgorithm;
+import io.jsonwebtoken.SignatureException;
+import io.jsonwebtoken.impl.crypto.MacProvider;
+
+import javax.crypto.spec.SecretKeySpec;
+import java.security.Key;
+import java.util.Date;
+
+public class Validator {
+
+    private static Key key = MacProvider.generateKey();
+    private final static long ttlMillis = 600000;
+
+    public static String generateToken(String username) {
+        SignatureAlgorithm signatureAlgorithm = SignatureAlgorithm.HS256;
+
+        long nowMillis = System.currentTimeMillis();
+        long expMillis = nowMillis + ttlMillis;
+        Date now = new Date(nowMillis);
+        Date exp = new Date(expMillis);
+
+        String jwt = Jwts.builder()
+                .setSubject(username)
+                .setIssuedAt(now)
+                .setExpiration(exp)
+                .signWith(signatureAlgorithm, key)
+                .compact();
+
+        return jwt;
+
+    }
+
+    public static String validate(String jwt) {
+        String subject = "unauthorized";
+
+        try {
+            Claims claims = Jwts.parser().setSigningKey(key).parseClaimsJws(jwt).getBody();
+            subject = claims.getSubject();
+            if (isExpired(claims.getExpiration())) {
+                subject = "expired";
+            }
+        } catch (SignatureException e) {
+            e.printStackTrace();
+        }
+
+        return subject;
+    }
+
+    private static boolean isExpired(Date expiration) {
+        long nowMillis = System.currentTimeMillis();
+        Date now = new Date(nowMillis);
+        return expiration.before(now);
+    }
+}