Defining classes runtime

Hi everybody!

I would like to know if there is a possibility to create new classes and make use of them during the runtime of an application. I have heard about Java Reflection API, can it be used to solve my problem ?

anybody?

Java reflection api is used for creating objects at rumtime , but the classes should be already available.It cannot create classes at runtime.It can load class , instantiate object and other related stuffs.

Why would you want to create a new class at runtime - why do you think that would be a useful feature?

Are you asking for auto generated files??

somewhere i read java file can created , compiled and executed at runtime using scripting languages

Yes, reflection gives you the methods for dynamically loading classes at runtime, and yes you can compile a class from within an application, so the parts are all there. It is not exactly simple.

You might find it a lot easier to use one of the scripting languages that can dynamically create scripts and be executed in the JVM. See Groovy, JPython, JRuby and probably a bunch more.

Bill

Thanks everybody. I'll look into those scripting languages. I wanted to know if there is a possibility to dynamically extend a Java program.
[ August 27, 2007: Message edited by: Yohan Liyanage ]

I've found the Javassist library very useful for this. Since it creates real Java classes, I'd think it would be much faster that anything that involves a scripting language (assuming that those are essentially interpreted, not compiled to bytecode).

I wanted to know if there is a possibility to dynamically extend a Java program

yes, you can dynamically extend java classes

Originally posted by harish thrivile:

yes, you can dynamically extend java classes

how ? and useful link for this.

I came across this article when I was searching the web for this problem.

Add dynamic Java code to your application By Li Yang :
http://www.javaworld.com/javaworld/jw-06-2006/jw-0612-dynamic.html

Originally posted by Rahul Bhattacharjee:
how ? and useful link for this.

As was said before, Javassist can do this. It comes with a tutorial that demonstrates how to do that.

Originally posted by Ulf Dittmer:

As was said before, Javassist can do this. It comes with a tutorial that demonstrates how to do that.

Thanks , I will lookinto it.Wasn't aware of this.