Postman pre-request script to automatically get a bearer token from Keycloak and save it for reuse

postman-pre-request-for-keycloak.js

const echoPostRequest = {
  url: '127.0.0.1:8180/auth/realms/master/protocol/openid-connect/token',
  method: 'POST',
  header: 'Content-Type:application/x-www-form-urlencoded',
  body: {
    mode: 'urlencoded',
    urlencoded: [
            { key: 'client_id', value: 'admin-cli' },
            { key: 'username', value: 'admin' },
            { key: 'password', value: 'admin' },
            { key: 'grant_type', value: 'password' }
    ]
  }
};

var getToken = true;

if (!pm.environment.get('accessTokenExpiry') || 
    !pm.environment.get('currentAccessToken')) {
    console.log('Token or expiry date are missing');
} else if (pm.environment.get('accessTokenExpiry') <= (new Date()).getTime() + 5000) {
    console.log('Token is expired or is going to expire in 5 seconds');
} else {
    getToken = false;
    console.log('Token and expiry date are all good');
}

if (getToken === true) {
    pm.sendRequest(echoPostRequest, function (err, res) {
    console.log(err ? err : res.json());
        if (err === null) {
            console.log('Saving the token and expiry date');
            var responseJson = res.json();
            pm.environment.set('currentAccessToken', responseJson.access_token);
    
            var expiryDate = new Date();
            expiryDate.setSeconds(expiryDate.getSeconds() + responseJson.expires_in);
            pm.environment.set('accessTokenExpiry', expiryDate.getTime());
        }
    });
}