How to load a .class file dynamically?

Question

Hello World ;)
Does anyone know, how I can create an object of a class, that was compiled during the runtime?
The facts:
- The user puts a grammar in. Saved to file. ANTLR generates Scanner and Parser (Java Code .java)
- I compile these file, so XYScanner.class and XYParser.class are available.
- Now I want to create an object of XYScanner (the classnames are not fixed, but I know the filename). I tried to call the constructor of XYScanner (using reflection) but nothing works and now I am really despaired!
Isn't there any way to instantiate the class in a way like
Class c = Class.forName("/home/mark/XYScanner");
c scan = new c("input.txt");
The normal call would be:
XYLexer lex = new XYLexer(new ANTLRFileStream("input.txt"));The problem using reflection is now that the parameter is a ANTLRFileStream, not only an Integer, as in this example shown:
Class cls = Class.forName("method2");
Class partypes[] = new Class[2];
partypes[0] = Integer.TYPE;
partypes[1] = Integer.TYPE;
Method meth = cls.getMethod("add", partypes);
method2 methobj = new method2();
Object arglist[] = new Object[2];
arglist[0] = new Integer(37);
arglist[1] = new Integer(47);
Object retobj = meth.invoke(methobj, arglist);
Integer retval = (Integer)retobj;
System.out.println(retval.intValue());Has anyone an idea? Thanks for each comment in advance!!!

Answer 1

Dump all of your class files into a directory.
Use the File class to list all files and iterateover
the files.NastyNot really, when you are dynamically creating code, I would expect the output to be centralized, not spread out all over the place.
>
Use a URLClassloader to load the URL that isobtained
for each file with file.toURI().toURL()(file.toURL()
is depricated in 1.6)Wrong, the URL you give it must be that of the
directory, not the class file.No, I did this quite recently, you can give it a specific class file to load.
>
Load all of the classes in this directory, thatway
any anonymous classes are loaded as well.Anonymous classes automatically loaded when the real
one isIt can't load it if it doesn't know where the code is. Since you haven't used a URL classloader to load once class file at a time, you would never encounter this. But if you loaded a class file that had an anonymous classfile it needed, would it know where to look for it?
>
From this point you should be able to just get a
class with Class.forName(name)No. Class.forName uses the classloader of the class
it's called in, which will be the system classloader.
It won't find classes loaded by a URLClassLoader.got me there.