Java examples for Reflection:Class Loader
Returns an instance of the given class name, by calling the default constructor.
/*//from w w w . j ava 2 s . c o m * $Id: ClassUtil.java 709153 2008-10-30 12:54:10Z apetrelli $ * * Licensed to the Apache Software Foundation (ASF) under one * or more contributor license agreements. See the NOTICE file * distributed with this work for additional information * regarding copyright ownership. The ASF licenses this file * to you 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. */ import java.lang.reflect.InvocationTargetException; import java.lang.reflect.Method; public class Main{ /** * Returns an instance of the given class name, by calling the default * constructor. * * @param className The class name to load and to instantiate. * @return The new instance of the class name. * @throws CannotInstantiateObjectException If something goes wrong during * instantiation. * @since 2.0.7 */ public static Object instantiate(String className) { return instantiate(className, false); } /** * Returns an instance of the given class name, by calling the default * constructor. * * @param className The class name to load and to instantiate. * @param returnNull If <code>true</code>, if the class is not found it * returns <code>true</code>, otherwise it throws a * <code>TilesException</code>. * @return The new instance of the class name. * @throws CannotInstantiateObjectException If something goes wrong during instantiation. * @since 2.0.7 */ public static Object instantiate(String className, boolean returnNull) { ClassLoader original = Thread.currentThread() .getContextClassLoader(); if (original == null) { Thread.currentThread().setContextClassLoader( ClassUtil.class.getClassLoader()); } try { Class<?> namedClass = Class.forName(className); return namedClass.newInstance(); } catch (ClassNotFoundException e) { if (returnNull) { return null; } throw new CannotInstantiateObjectException( "Unable to resolve factory class: '" + className + "'", e); } catch (IllegalAccessException e) { throw new CannotInstantiateObjectException( "Unable to access factory class: '" + className + "'", e); } catch (InstantiationException e) { throw new CannotInstantiateObjectException( "Unable to instantiate factory class: '" + className + "'. Make sure that this class has a default constructor", e); } finally { // If the original context classloader of the current thread was // null, it must be reset. if (original == null) { Thread.currentThread().setContextClassLoader(null); } } } }