Java Core Program :: Dynamic Object Creation for Classe & Invoking the same

Question

Hi,
I need to create a dynamic object for a class & invoke it.
For eg: I have a table in my DB where all the names of my java classes are stored. I need to call name from the table of the DB and call that class dynamically in my java program.
ResultSet_01 = executeQuery("select classname from class_table where class_descrip = 'Sales Invoice' ");
               while(ResultSet_01.next())
                    String class_name = ResultSet_01.getDouble("classname");
               }Now using the string in class_name that is fetched from ResultSet_01, I need to create an object for the class_name & invoke the class that is been created with the same name.
Thank in advance.
Regards,
Haider Imani

Answer 1

Well for a start since a class name is a String, not a number you'd better start by getting the name with getString() not getDouble().
You need to work with fully qualified names, (FQNs) like "com.acme.myproject.MyDynamicClass", not just the bare MyDynamicClass.
The next question is where the .class files for the dynamically loaded classes are stored. If they are part of your normal program code, on the class path, then you can use Class.forName to load the class and return a Class object. If they are in some special place you'll need to create a URLClassLoader and get the Class from that.
Generally, when you load a class this way, it should implement some known interface, or extend some know abstract class. By placing objects of the dynamic class in a reference to that interface you can use the methods defined in the interface.
The usual way of getting an instance of a dynamic class is to call newInstance() on the Class object.