ReflectionUtil.java

/*
 * Copyright 2016 Christoph Böhme
 *
 * Licensed under the Apache License, Version 2.0 the "License";
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.culturegraph.mf.commons.reflection;

/**
 * Utility functions for dynamically loading classes and calling setters on
 * them.
 *
 * @author Christoph Böhme
 */
public final class ReflectionUtil {

	private ReflectionUtil() {
		throw new AssertionError("No instances allowed");
	}

	public static ClassLoader getContextClassLoader() {
		final ClassLoader loader = Thread.currentThread().getContextClassLoader();
		if (loader == null) {
			throw new ReflectionException("Class loader could not be found.");
		}
		return loader;
	}

	public static <T> ConfigurableClass<? extends T> loadClass(String className,
			Class<T> baseType) {
		return loadClass(getContextClassLoader(), className, baseType);
	}

	public static <T> ConfigurableClass<? extends T> loadClass(ClassLoader loader,
			String className, Class<T> baseType) {
		final Class<?> clazz;
		try {
			clazz = loader.loadClass(className);
		} catch (ClassNotFoundException e) {
			throw new ReflectionException("Class not found: " + className, e);
		}
		if (!baseType.isAssignableFrom(clazz)) {
			throw new ReflectionException(className + " must extend or implement " +
					baseType.getName());
		}
		@SuppressWarnings("unchecked")  // protected by isAssignableFrom check
		final Class<? extends T> castedClass = (Class<? extends T>) clazz;
		return new ConfigurableClass<>(castedClass);
	}

}