@Grab('io.jsonwebtoken:jjwt:0.7.0')
import io.jsonwebtoken.*

def secret = 'password'
def payload = [
    id: '123',
    name: 'Jon Doe',
    email: 'jon@doe.com'
]

def jwt = Jwts.builder().setClaims(payload).signWith(SignatureAlgorithm.HS256, secret.bytes).compact();

println jwt

Jwts.parser().setSigningKey(secret.bytes).parseClaimsJws(jwt).body