How to do it...

1. Let's create a User class as a model for our JSON message:

public class User {

    private String name;
    private String email;

    public User(){        
    }

    public User(String name, String email) {
        this.name = name;
        this.email = email;
    }

    @Override
    public String toString() {
        return "User{" + "name=" + name + ", email=" + email + '}';
    }

    //DON'T FORGET THE GETTERS AND SETTERS
    //THIS RECIPE WON'T WORK WITHOUT THEM

}

2. Then, let's create a class to use JSON-B to transform an object:

public class JsonBUser {
    
    public static void main(String[] args) throws Exception {
        User user = new User("Elder", "elder@eldermoraes.com");
        
        Jsonb jb = JsonbBuilder.create();
        String jsonUser = jb.toJson(user);
        User u = jb.fromJson(jsonUser, User.class);
        
        jb.close();
        System.out.println("json: " + jsonUser);
        System.out.println("user: " + u);
        
    }
}

The result printed is:

json: {"email":"elder@eldermoraes.com","name":"Elder"}
 user: User{name=Elder, email=elder@eldermoraes.com}

The first line is the object transformed into a JSON string. The second is the same string converted into an object.