How to load an arbitrary java .class file from the filesystem and reflect on it?

Question

I want to make a command-line utility that does some operations based on reflection of external class files. I would pass in a path to .class files or source files(possibly wildcards). At some point during the execution, I need to get Class objects for each class, not knowing their package names beforehand. What would it take to do this? What can I look at to get started? I also have access to the classes' source files.

this is in java 1.6.

also, would it be easier to get class objects from the source by using the java compiler API?

Answer 1

You will need to create a ClassLoader and use defineClass to create a Class from the file you've read. Add dynamic Java code to your application is an interesting to read about such things, it even describes the compilation of the sources.

Answer 2

If you don't know the name of the package, you can find that out by reading the file with an appropriate library, such as ObjectWeb's ASM. In fact, if you are just trying to find out information about the class file, then you might not want to use reflection at all.