edu.pdx.cs.joy.reflect.LoggingClassLoader Maven / Gradle / Ivy
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package edu.pdx.cs.joy.reflect;
import java.io.File;
import java.net.*;
/**
* This ClassLoader prints out the name of every class
* that it (or its parent) loads.
*/
public class LoggingClassLoader extends URLClassLoader {
/**
* Creates a LoggingClassLoader that loads classes from
* a given array of URLs. However, before this class loader
* attempts to load the class, it will delegate to its parent class
* loader.
*/
public LoggingClassLoader(URL[] urls, ClassLoader parent) {
super(urls, parent);
}
/**
* Invoked as this class loader is loading a class
*/
public Class loadClass(String className)
throws ClassNotFoundException {
System.out.println("Loading " + className);
return super.loadClass(className);
}
/**
* Main program that uses a LoggingClassLoader to load
* the class with the given name from a given location.
*/
public static void main(String[] args) {
File file = new File(args[0]);
String className = args[1];
try {
URL[] urls = new URL[] { file.toURL() };
ClassLoader parent = ClassLoader.getSystemClassLoader();
ClassLoader cl = new LoggingClassLoader(urls, parent);
cl.loadClass(className);
} catch (MalformedURLException ex) {
String s = "Bad URL: " + ex;
System.err.println(s);
} catch (ClassNotFoundException ex) {
String s = "Could not find class " + className;
System.err.println(s);
}
}
}