package cl;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;

public class CustomClassLoader extends ClassLoader
{
	public CustomClassLoader(){
		super(CustomClassLoader.class.getClassLoader());
	}
	
	public Class loadClass( String name, boolean resolve ) 
	   throws  ClassNotFoundException {
		// Our goal is to get a Class object
		Class clazz = null;
		
		// First, see if we've already dealt with this one
		clazz = findLoadedClass(name);
		
		String fileStub = name.replace( '.', '/' );
		String classFilename = "target/classes/" + fileStub+".class";
		
		try {
			// read the bytes
			byte raw[] = getBytes( classFilename );
			// try to turn them into a class
			clazz = defineClass( name, raw, 0, raw.length );
		} catch( IOException ex ) {
			// This is not a failure! If we reach here, it might
			// mean that we are dealing with a class in a library,
			// such as java.lang.Object
		}		
		
		// Maybe the class is in a library -- try loading
		// the normal way
		if (clazz==null) {
		    clazz = findSystemClass( name );
		}
		
		// Resolve the class, if any, but only if the "resolve"
		// flag is set to true
		if (resolve && clazz != null) {
		    resolveClass( clazz );
		}
		
		// If we still don't have a class, it's an error
		if (clazz == null) {
			throw new ClassNotFoundException( name );
		}
		
		return clazz;
	}
	
	// Given a filename, read the entirety of that file from disk
	// and return it as a byte array.
	private byte[] getBytes( String filename ) throws IOException {
		// Find out the length of the file
		File file = new File( filename );
		long len = file.length();
		
		// Create an array that's just the right size for the file's
		// contents
		byte raw[] = new byte[(int)len];
		
		// Open the file
		FileInputStream fin = new FileInputStream( file );
		
		// Read all of it into the array; if we don't get all,
		// then it's an error.
		int r = fin.read( raw );
		
		if (r != len) {
			throw new IOException( "Can't read all, "+r+" != "+len );
		}
		
		// Don't forget to close the file!
		fin.close();
		
		// And finally return the file contents as an array
		return raw;
	}	
}