How to set userData with the Box2DMapObjectParser

/* In the properties of an object in the Tiled editor, you can use Aliases#userData.
 * for example:
 * userData: some string
 * or like this:
 * userData: 1
 *
 * If you create the map programmatically you can set any Objects like e.g. a Sprite as user data of course. */

// Then the user data will be where you put it in.
Body body = parser.getBodies().get("some body");
Object userData = body.getUserData();

// The same works for fixtures and joints.
Fixture fixture = parser.getFixtures().get("some fixture");
Object userData = fixture.getUserData()

Joint joint = parser.getJoints().get("some joint");
Object userData = joint.getUserData();