{
    "result":{
        "birthday_at":"0000-00-00",
        "first_name":"Serhiy",
        "level":5,
        "last_name":"Radkivskiy",
        "gender":0
    },
    "cmd":"INFO",
    "service":{
        "code":0,
        "error_desc":""
    }
}

public class UserInfo
{
  public Date birthday_at;
  public String first_name;
  public String last_name;
  public int level;
  public int gender;
}

import com.adobe.serialization.json

var obj:Object = JSON.decode( jsonString );
var user:UserInfo = new UserInfo();

for ( var prop:String in obj )
    user[prop] = obj[prop];