Java Class.forName() from distant directory

问题

I am currently loading Java classes using Class.forName() to load it.

clazz = Class.forName("interfaces.MyClass");

But now I want to load classes from different directory, I have tried to set classpath by

clazz = Class.forName("-cp \"C:/dir\" distantinterfaces.DistantClass");

With no success and ClassNotFoundException. Full path to distant class is:

C:/dir/distantinterfaces/DistantClass.class

回答1:

Use an URLClassLoader for this. The code might be something along the lines of:

File f = new File("C:/dir");
URL[] cp = {f.toURI().toURL()};
URLClassLoader urlcl = new URLClassLoader(cp);
Class clazz = urlcl.loadClass("distantinterfaces.DistantClass");

回答2:

Either the directory is in the classpath, and you can use Class.forName() (which only accepts fuly qualified name classes, and not -cp command line options), or it's not in the classpath and you should then use a custom class loader.

You're not saying what you really want to do (why are you loading classes dynamically), but your best bet is to have the directory in the classpath.

回答3:

You have to create an instance of ClassLoader which is aware of the directory with classes. See stackoverflow questions tagged urlclassloader.

来源：https://stackoverflow.com/questions/16335305/java-class-forname-from-distant-directory