Making a class loader

Question

I am developing a class loader that will load plugins into my software. I have a jar file with two things in it, the package containing my code, and a text file containing the name of the class that I want to load from the jar. Is there a way for my app to read the text in the file and get the class name, then load the class with that name from the jar file?

I think you just have to write it. What is your problem ? Your entry point will be a class that reads the text file, loads the classes and then does whatever you want — Dici, Jan 04 '15 at 20:05
I think that this [answer][1] should suffice. It is that easy. [1]: http://stackoverflow.com/questions/9819318/create-new-classloader-to-reload-class — Alessandro Santini, Jan 04 '15 at 20:06

score 0 · Accepted Answer · answered Jan 04 '15 at 20:25

This is the code that works:

content = new Scanner(new File("plugins/" + listOfFiles[i].getName().replaceAll(".jar", "") + "/" + "plugin.cfg")).useDelimiter("\\Z").next();

URL[] urls = null;
try {
    File dir = new File("plugins/" + listOfFiles[i].getName());
    URL url = dir.toURL();
    urls = new URL[]{url};
} catch (MalformedURLException e) {

}

try {
    ClassLoader cl = new URLClassLoader(urls);
    Class cls = cl.loadClass(content.replaceAll("Main-Class:", ""));
    Method enable = cls.getMethod("enable", (Class<?>[]) null);
    enable.invoke(enable, null);
}catch (Exception e) {
    System.out.println("One of the installed plugins might have an invalid plugin.cfg.");
}

The code reads a file with the name of the main class in it, and then loads that class from the jar file it extracted earlier.

Making a class loader

1 Answers1