jwt.groovy

  @Grab(group='io.jsonwebtoken', module='jjwt-api', version='0.11.2')
  @Grab(group='io.jsonwebtoken', module='jjwt-impl', version='0.11.2')
  @Grab(group='io.jsonwebtoken', module='jjwt-jackson', version='0.11.2')

import io.jsonwebtoken.Claims;
import io.jsonwebtoken.ExpiredJwtException;
import io.jsonwebtoken.Jws;
import io.jsonwebtoken.Jwts;
import io.jsonwebtoken.security.Keys;
import io.jsonwebtoken.security.SignatureException;

import io.jsonwebtoken.SignatureAlgorithm

import java.time.Instant
import java.time.OffsetDateTime
import java.time.ZoneOffset
import java.time.Duration
import java.util.stream.Collectors
import java.nio.ByteBuffer

def random = new Random()
def buffer = ByteBuffer.allocate(8 * 4)

random.longs()
  .filter { it >= 0 }
  .limit(4)
  .forEach { buffer.putLong(it) }

def bytes = buffer.array()

def now = OffsetDateTime.now(ZoneOffset.UTC)
def exp = (now + Duration.ofHours(2)).toInstant()

Jwts.builder()
  .setSubject('user')
  .setExpiration(Date.from(exp))
  .setIssuedAt(Date.from(now.toInstant()))
  .setIssuer('https://example.com')
  .signWith(SignatureAlgorithm.RS256, bytes)
  .compact()