ExceptionUtils.java

/****************************************************************************
 * Copyright (C) 2013 ecsec GmbH.
 * All rights reserved.
 * Contact: ecsec GmbH (info@ecsec.de)
 *
 * This file is part of the Open eCard App.
 *
 * GNU General Public License Usage
 * This file may be used under the terms of the GNU General Public
 * License version 3.0 as published by the Free Software Foundation
 * and appearing in the file LICENSE.GPL included in the packaging of
 * this file. Please review the following information to ensure the
 * GNU General Public License version 3.0 requirements will be met:
 * http://www.gnu.org/copyleft/gpl.html.
 *
 * Other Usage
 * Alternatively, this file may be used in accordance with the terms
 * and conditions contained in a signed written agreement between
 * you and ecsec GmbH.
 *
 ***************************************************************************/

package org.openecard.common.util;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;


/**
 * Collection of utility functions for exception processing.
 *
 * @author Tobias Wich <tobias.wich@ecsec.de>
 */
public class ExceptionUtils {

    /**
     * Checks the given exception's cause path for the given types.
     * The types are checked in reverse order, meaning the last given type is the expected type of first cause. When the
     * cause path is as expected, the returned object is cast to the expected type.<br/>
     * The function works when the given types are not {@code Throwable} classes, however in that case it will never
     * return an object.
     *
     * @param <T> Return type of the expected Throwable object.
     * @param <C> Typed class of the expected Throwable object.
     * @param ex The root exception whose cause path should be checked.
     * @param returnClass Typed class of the expected Throwable object.
     * @param cs Classes of the Throwables in between the path.
     * @return The expected Throwable object, or null if the path is not correctly typed or does not exist.
     */
    public static <T extends Throwable, C extends Class<T>> T matchPath(Throwable ex, C returnClass,
	    Class<?>... cs) {
	// TODO: optimize reverse processing
	ArrayList<Class<?>> classList = new ArrayList<Class<?>>(cs.length);
	classList.addAll(Arrays.asList(cs));
	Collections.reverse(classList);
	// trace back exceptions in list
	for (Class<?> next : classList) {
	    Throwable nextEx = ex.getCause();
	    if (! (nextEx != null && next.isInstance(nextEx))) {
		// instance not of the desired type or not existing
		return null;
	    }
	    ex = nextEx;
	}
	// check last instance for the desired type
	Throwable nextEx = ex.getCause();
	if (! (nextEx != null && returnClass.isInstance(nextEx))) {
	    // instance not of the desired type or not existing
	    return null;
	}
	return returnClass.cast(nextEx);
    }

}