Setup publish over ftp plugin configuration with groovy.

configureFTP.groovy

import hudson.util.Secret;
import jenkins.plugins.publish_over_ftp.BapFtpHostConfiguration;
import jenkins.plugins.publish_over_ftp.options.FtpPluginDefaults;
import net.sf.json.JSONObject;
import org.kohsuke.stapler.StaplerRequest;
import jenkins.model.*;

// Plugin configuration
def connectionName = "ftp";
def hostname = "mydomain.com";
def username = "user";
def encryptedPassword = new Secret("password").getEncryptedValue();
def remoteRootDir = "/";
def port = 21;
def timeout = 300000;
def useActiveData = false;
def encoding = "UTF-8";
def disableMakeNestedDirs = false;
def disableRemoteVerification = false;

def plugin = Jenkins.getInstance().getDescriptor("jenkins.plugins.publish_over_ftp.BapFtpPublisherPlugin");

StaplerRequest req = [
  bindJSONToList: { a, b ->
    return new Collections.SingletonList(new BapFtpHostConfiguration(connectionName, hostname, username, encryptedPassword,
      remoteRootDir, port, timeout, useActiveData, encoding, disableMakeNestedDirs, disableRemoteVerification));
  },
  bindJSON      : { a, b ->
    return new FtpPluginDefaults();
  }
] as StaplerRequest;

plugin.configure(req, new JSONObject());
plugin.save();
println "FTP Publisher successfully configured.";