ContextClassloader.java

package main;

import java.util.Hashtable;
import java.io.ByteArrayInputStream;
import java.io.FileInputStream;

public class ContextClassloader extends ClassLoader {
    private Hashtable classes = new Hashtable();

    public ContextClassloader() {
    }

    /**
     * This sample function for reading class implementations reads
     * them from the local file system
     */
    private byte getClassImplFromDataBase(String className)[] {
    	System.out.println("        >>>>>> Fetching the implementation of "+className);
    	byte result[];
    	try {
    	    FileInputStream fi = new FileInputStream("store\\"+className+".impl");
    	    result = new byte[fi.available()];
    	    fi.read(result);
    	    return result;
    	} catch (Exception e) {

    	    /*
    	     * If we caught an exception, either the class wasnt found or it
    	     * was unreadable by our process.
    	     */
    	    return null;
    	}
    }

    /**
     * This is a simple version for external clients since they
     * will always want the class resolved before it is returned
     * to them.
     */
    public Class loadClass(String className) throws ClassNotFoundException {
        return (loadClass(className, true));
    }

    /**
     * This is the required version of loadClass which is called
     * both from loadClass above and from the internal function
     * FindClassFromClass.
     */
    public synchronized Class loadClass(String className, boolean resolveIt)
    	throws ClassNotFoundException {
        Class result;
        byte  classData[];

        System.out.println("        >>>>>> Load class : "+className);

        if(className == "railo.loader.servlet.CFMLServlet") {        	
        	/* Check our local cache of classes */
        	result = (Class)classes.get(className);
        	if (result != null) {
        		System.out.println("        >>>>>> returning cached result.");
        		return result;
        	}
            /* Try to load it from our repository */
            classData = getClassImplFromDataBase(className);
            if (classData == null) {
                throw new ClassNotFoundException();
            }

            /* Define it (parse the class file) */
            result = defineClass(classData, 0, classData.length);
            if (result == null) {
                throw new ClassFormatError();
            }

            if (resolveIt) {
                resolveClass(result);
            }

            classes.put(className, result);
            System.out.println("        >>>>>> Returning newly loaded class.");
        }
        

        /* Check with the primordial class loader */
        try {
            result = super.findSystemClass(className);
            System.out.println("        >>>>>> returning system class (in CLASSPATH).");
            return result;
        } catch (ClassNotFoundException e) {
        	System.out.println("        >>>>>> Not a system class.");
            throw new ClassNotFoundException();
        }

    }
}