ReflectionUtils.java

/*******************************************************************************
 * Copyright (c) 2014, 2015 itemis AG and others.
 *
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     Jan Köhnlein (itemis AG) - initial API and implementation (#427106)
 *     Matthias Wienand (itemis AG) - add methods and javadoc
 *
 *******************************************************************************/
package org.eclipse.gef.common.reflect;

import java.lang.reflect.Field;

/**
 * Allows to access the value of private fields.
 *
 * @author Jan Koehnlein
 * @author mwienand
 * 
 */
public class ReflectionUtils {

	/**
	 * Returns the value of the specified private field for the given
	 * <i>owner</i>.
	 * 
	 * @param <T>
	 *            The type of the field value.
	 * 
	 * @param owner
	 *            {@link Object} from which the field is read.
	 * @param fieldName
	 *            Name of the field to read.
	 * @return The value of the specified field for the given <i>owner</i>.
	 */
	@SuppressWarnings("unchecked")
	public static <T> T getPrivateFieldValue(Object owner, String fieldName) {
		Field field = getPrivateField(owner, fieldName);
		try {
			return (T) field.get(owner);
		} catch (IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

	/**
	 * Tries to find the field specified by <i>fieldName</i> in the class
	 * hierarchy of the given <i>owner</i>. If the field can be found, it is
	 * made accessible, so that its value can be read and written.
	 * 
	 * @param owner
	 *            {@link Object} from which the {@link Field} should be
	 *            extracted.
	 * @param fieldName
	 *            The name of the field.
	 * @return {@link Field} if it can be found, otherwise <code>null</code>.
	 */
	public static Field getPrivateField(Object owner, String fieldName) {
		Class<? extends Object> currentClass = owner.getClass();
		Field field = null;
		do {
			try {
				field = currentClass.getDeclaredField(fieldName);
			} catch (NoSuchFieldException e) {
				currentClass = currentClass.getSuperclass();
				if (currentClass == null) {
					return null;
				}
			}
		} while (field == null);
		field.setAccessible(true);
		return field;
	}

	/**
	 * Sets the value of the specified private field for the given <i>owner</i>
	 * to the given <i>value</i>.
	 * 
	 * @param <T>
	 *            The type of the field value.
	 * 
	 * @param owner
	 *            {@link Object} for which the field is set.
	 * @param fieldName
	 *            Name of the field.
	 * @param value
	 *            New value for the field.
	 */
	public static <T> void setPrivateFieldValue(Object owner, String fieldName,
			T value) {
		Field field = getPrivateField(owner, fieldName);
		try {
			field.set(owner, value);
		} catch (IllegalAccessException e) {
			throw new RuntimeException(e);
		}
	}

}