jenkins script get credentials to json string

jenkins_script_get_credentials_to_json_string.groovy

import groovy.json.JsonOutput
def get_credentials() {
    def creds = com.cloudbees.plugins.credentials.CredentialsProvider.lookupCredentials(
        com.cloudbees.plugins.credentials.common.StandardUsernameCredentials.class,
        Jenkins.instance,
        null,
        null
    )
    credentials = []
    for(c in creds) {
        def cred = [:]
        if(c instanceof com.cloudbees.jenkins.plugins.sshcredentials.impl.BasicSSHUserPrivateKey){
            cred['type'] = 'BasicSSHUserPrivateKey'
            attrs = cred['attrs'] = [:]
            attrs['id'] = c.id
            attrs['desc'] = c.description
            attrs['privateKeys'] = c.privateKeySource.getPrivateKeys()
            attrs['passphrase'] = c.getPassphrase()
            attrs['privateKey'] = c.getPrivateKey()
            attrs['isUsernameSecret'] = c.isUsernameSecret()
            attrs['username'] = c.getUsername()
            attrs['scope'] = c.getScope()
        }
        if (c instanceof com.cloudbees.plugins.credentials.impl.UsernamePasswordCredentialsImpl){
            cred['type'] = 'UsernamePasswordCredentialsImpl'
            attrs = cred['attrs'] = [:]
            attrs['id'] = c.id
            attrs['desc'] = c.description
            attrs['username'] = c.username
            attrs['password'] = c.password
            attrs['isUsernameSecret'] = c.isUsernameSecret()
            attrs['scope'] = c.getScope()
        }
        credentials.add(cred)
    }
    return JsonOutput.toJson(credentials)
}
print(get_credentials())