import io.jsonwebtoken.SigningKeyResolverAdapter; //导入依赖的package包/类
private Jws<Claims> parseTokenFromBase64EncodedString(final String base64EncodedToken) throws JwtException {
    try {
        return Jwts.parser().setSigningKeyResolver(new SigningKeyResolverAdapter() {
            @Override
            public byte[] resolveSigningKeyBytes(JwsHeader header, Claims claims) {
                final String identity = claims.getSubject();

                // Get the key based on the key id in the claims
                final String keyId = claims.get(KEY_ID_CLAIM, String.class);
                final Key key = keyService.getKey(keyId);

                // Ensure we were able to find a key that was previously issued by this key service for this user
                if (key == null || key.getKey() == null) {
                    throw new UnsupportedJwtException("Unable to determine signing key for " + identity + " [kid: " + keyId + "]");
                }

                return key.getKey().getBytes(StandardCharsets.UTF_8);
            }
        }).parseClaimsJws(base64EncodedToken);
    } catch (final MalformedJwtException | UnsupportedJwtException | SignatureException | ExpiredJwtException | IllegalArgumentException e) {
        // TODO: Exercise all exceptions to ensure none leak key material to logs
        final String errorMessage = "Unable to validate the access token.";
        throw new JwtException(errorMessage, e);
    }
}
 

import io.jsonwebtoken.SigningKeyResolverAdapter; //导入依赖的package包/类
private static Claims getBody(String jwt) {
  return Jwts.parser()
    .setSigningKeyResolver(new SigningKeyResolverAdapter() {
        @Override
        public Key resolveSigningKey(JwsHeader header, Claims claims) {
          String subject = claims.getSubject();
          if (subject == null || subject.isEmpty()) 
            throw new MissingClaimException(header, claims, "Subject is not provided in JWT.");

          if (!userToKeyMap.containsKey(subject)) 
            throw new SignatureException("Signing key is not reqistred for the subject.");
          
          return userToKeyMap.get(subject);
        }})
    .parseClaimsJws(jwt)
    .getBody();   
}
 

import io.jsonwebtoken.SigningKeyResolverAdapter; //导入依赖的package包/类
/**
 * Gets the value of the <em>exp</em> claim of a JWT.
 * 
 * @param token The token.
 * @return The expiration.
 * @throws NullPointerException if the token is {@code null}.
 * @throws IllegalArgumentException if the given token contains no <em>exp</em> claim.
 */
public static final Date getExpiration(final String token) {

    if (token == null) {
        throw new NullPointerException("token must not be null");
    }

    final AtomicReference<Date> result = new AtomicReference<>();

    try {
        Jwts.parser().setSigningKeyResolver(new SigningKeyResolverAdapter() {

            @SuppressWarnings("rawtypes")
            @Override
            public Key resolveSigningKey(JwsHeader header, Claims claims) {
                Date exp = claims.getExpiration();
                if (exp != null) {
                    result.set(exp);
                }
                return DUMMY_KEY;
            }
        }).parse(token);
    } catch (JwtException e) {
        // expected since we do not know the signing key
    }

    if (result.get() == null) {
        throw new IllegalArgumentException("token contains no exp claim");
    } else {
        return result.get();
    }
}