jwt service

src/main/java/io/spring/application/JwtService.java

@@ -2,6 +2,10 @@ package io.spring.application;
 
 import io.spring.application.user.UserData;
 
+import java.util.Optional;
+
 public interface JwtService {
     String toToken(UserData userData);
+
+    Optional<String> getSubFromToken(String token);
 }

src/main/java/io/spring/infrastructure/service/DefaultJwtService.java

@@ -0,0 +1,49 @@
+package io.spring.infrastructure.service;
+
+import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Jws;
+import io.jsonwebtoken.Jwts;
+import io.jsonwebtoken.SignatureAlgorithm;
+import io.jsonwebtoken.SignatureException;
+import io.spring.application.JwtService;
+import io.spring.application.user.UserData;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Service;
+
+import java.util.Date;
+import java.util.Optional;
+
+@Service
+public class DefaultJwtService implements JwtService {
+    private String secret;
+    private int sessionTime;
+
+    public DefaultJwtService(@Value("${jwt.secret}") String secret,
+                             @Value("${jwt.sessionTime}") int sessionTime) {
+        this.secret = secret;
+        this.sessionTime = sessionTime;
+    }
+
+    @Override
+    public String toToken(UserData userData) {
+        return Jwts.builder()
+            .setSubject(userData.getUsername())
+            .setExpiration(expireTimeFromNow())
+            .signWith(SignatureAlgorithm.HS512, secret)
+            .compact();
+    }
+
+    @Override
+    public Optional<String> getSubFromToken(String token) {
+        try {
+            Jws<Claims> claimsJws = Jwts.parser().setSigningKey(secret).parseClaimsJws(token);
+            return Optional.ofNullable(claimsJws.getBody().getSubject());
+        } catch (Exception e) {
+            return Optional.empty();
+        }
+    }
+
+    private Date expireTimeFromNow() {
+        return new Date(System.currentTimeMillis() + sessionTime * 1000);
+    }
+}