Script for generating a JWT token.

GenerateJWT.groovy

import javax.crypto.Mac
import javax.crypto.spec.SecretKeySpec
@Grab(group='commons-codec', module='commons-codec', version='1.10')
import org.apache.commons.codec.binary.Base64

def jwtTokenHeader = '''{
  "typ": "JWT",
  "alg": "HS256"
}'''

def jwtTokenClaims = """{
  "exp": ${Long.MAX_VALUE},
  "userName": "test",
  "otherInfo": 12
}"""

try {
    String secret = 'secret'
    String message = Base64.encodeBase64String(jwtTokenHeader.bytes) + '.' + Base64.encodeBase64String(jwtTokenClaims.bytes)
    
    Mac sha256_HMAC = Mac.getInstance('HmacSHA256')
    SecretKeySpec key = new SecretKeySpec(secret.bytes, 'HmacSHA256')
    sha256_HMAC.init(key)
    
    String hash = Base64.encodeBase64String(sha256_HMAC.doFinal(message.bytes))
    println "${message}.${hash}"
}
catch (e) {
    e.printStackTrace()
}