Reflection is a powerful thing to get extended class info at runtime. If you are loaded classes into your application dynamically then Java Reflection is the right thing to get the structure of the classes. Reflection uses java class: Class. The object of the 'Class class' can hold all the information of the class and have getter methods to extract and manipulate this information.
// Creates an object of Class String
Class cl = Class.forName("java.lang.String");
// returns all the constructors of the class.
Constructor cnst [] = cl.getConstructors();
// returns all the declared fields of the class.
Field fld [] = cl.getDeclaredFields();