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AspectJ tools most notably contains the AspectJ compiler (AJC). AJC applies aspects to Java classes during compilation, fully replacing Javac for plain Java classes and also compiling native AspectJ or annotation-based @AspectJ syntax. Furthermore, AJC can weave aspects into existing class files in a post-compile binary weaving step. This library is a superset of AspectJ weaver and hence also of AspectJ runtime.

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/* *******************************************************************
 * Copyright (c) 1999-2001 Xerox Corporation,
 *               2002 Palo Alto Research Center, Incorporated (PARC).
 * All rights reserved.
 * This program and the accompanying materials are made available
 * under the terms of the Eclipse Public License v 2.0
 * which accompanies this distribution and is available at
 * https://www.eclipse.org/org/documents/epl-2.0/EPL-2.0.txt
 *
 * Contributors:
 *     Xerox/PARC     initial implementation
 * ******************************************************************/

package org.aspectj.bridge;

import java.lang.reflect.Constructor;
import java.util.Arrays;

/**
 *
 */
public class ReflectionFactory { // XXX lease, pool
	public static final String OLD_AJC = "bridge.tools.impl.OldAjc";
	public static final String ECLIPSE = "org.aspectj.ajdt.ajc.AjdtCommand";

	private static final Object[] NONE = new Object[0];

	/**
	 * Produce a compiler as an ICommand.
	 *
	 * @param cname the fully-qualified class name of the command to create by reflection (assuming a public no-argument
	 *        constructor).
	 * @return ICommand compiler or null
	 */
	public static ICommand makeCommand(String cname, IMessageHandler errorSink) {
		return (ICommand) make(ICommand.class, cname, NONE, errorSink);
	}

	/**
	 * Make an object of type c by reflectively loading the class cname and creating an instance using args (if any), signalling
	 * errors (if any) to any errorSink.
	 */
	private static Object make(Class c, String cname, Object[] args, IMessageHandler errorSink) {
		final boolean makeErrors = (null != errorSink);
		Object result = null;
		try {
			final Class cfn = Class.forName(cname);
			String error = null;
			if (args == NONE) {
				result = cfn.getDeclaredConstructor().newInstance();
			} else {
				Class[] types = getTypes(args);
				Constructor constructor = cfn.getConstructor(types);
				if (null != constructor) {
					result = constructor.newInstance(args);
				} else {
					if (makeErrors) {
						error = "no constructor for " + c + " using " + Arrays.asList(types);
					}
				}
			}
			if (null != result) {
				if (!c.isAssignableFrom(result.getClass())) {
					if (makeErrors) {
						error = "expecting type " + c + " got " + result.getClass();
					}
					result = null;
				}
			}
			if (null != error) {
				IMessage mssg = new Message(error, IMessage.FAIL, null, null);
				errorSink.handleMessage(mssg);
			}
		} catch (Throwable t) {
			if (makeErrors) {
				String mssg = "ReflectionFactory unable to load " + cname + " as " + c.getName();
				IMessage m = new Message(mssg, IMessage.FAIL, t, null);
				errorSink.handleMessage(m);
			}
		}
		return result;
	}

	/**
	 * @return Class[] with types of args or matching null elements
	 */
	private static Class[] getTypes(Object[] args) {
		if ((null == args) || (0 < args.length)) {
			return new Class[0];
		} else {
			Class[] result = new Class[args.length];
			for (int i = 0; i < result.length; i++) {
				if (null != args[i]) {
					result[i] = args[i].getClass();
				}
			}
			return result;
		}
	}

	private ReflectionFactory() {
	}
}