| /* |
| * 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. |
| */ |
| package org.ki.util; |
| |
| import org.apache.commons.logging.Log; |
| import org.apache.commons.logging.LogFactory; |
| |
| import java.io.InputStream; |
| import java.lang.reflect.Constructor; |
| |
| /** |
| * Utility method library used to conveniently interact with <code>Class</code>es, such as acquiring them from the |
| * application <code>ClassLoader</code>s and instantiating Objects from them. |
| * |
| * @author Les Hazlewood |
| * @since 0.1 |
| */ |
| public class ClassUtils { |
| |
| //TODO - complete JavaDoc |
| |
| /** Private internal log instance. */ |
| private static final Log log = LogFactory.getLog(ClassUtils.class); |
| |
| /** |
| * Returns the specified resource by checking the current thread's |
| * {@link Thread#getContextClassLoader() context class loader}, then the |
| * current ClassLoader (<code>ClassUtils.class.getClassLoader()</code>), then the system/application |
| * ClassLoader (<code>ClassLoader.getSystemClassLoader()</code>, in that order, using |
| * {@link ClassLoader#getResourceAsStream(String) getResourceAsStream(name)}. |
| * |
| * @param name the name of the resource to acquire from the classloader(s). |
| * @return the InputStream of the resource found, or <code>null</code> if the resource cannot be found from any |
| * of the three mentioned ClassLoaders. |
| * @since 0.9 |
| */ |
| public static InputStream getResourceAsStream(String name) { |
| InputStream is = null; |
| ClassLoader cl = Thread.currentThread().getContextClassLoader(); |
| if (cl != null) { |
| is = cl.getResourceAsStream(name); |
| } |
| |
| if (is == null) { |
| if (log.isTraceEnabled()) { |
| log.trace("Resource [" + name + "] was not found via the thread context ClassLoader. Trying the " + |
| "current ClassLoader..."); |
| } |
| cl = ClassUtils.class.getClassLoader(); |
| is = cl.getResourceAsStream(name); |
| if (is == null) { |
| if (log.isTraceEnabled()) { |
| log.trace("Resource [" + name + "] was not found via the current class loader. Trying the " + |
| "system/application ClassLoader..."); |
| } |
| cl = ClassLoader.getSystemClassLoader(); |
| is = cl.getResourceAsStream(name); |
| if (is == null && log.isTraceEnabled()) { |
| log.trace("Resource [" + name + "] was not found via the thread context, current, or " + |
| "system/application ClassLoaders. All heuristics have been exhausted. Returning null."); |
| } |
| } |
| } |
| return is; |
| } |
| |
| /** |
| * Attempts to load the specified class name from the current thread's |
| * {@link Thread#getContextClassLoader() context class loader}, then the |
| * current ClassLoader (<code>ClassUtils.class.getClassLoader()</code>), then the system/application |
| * ClassLoader (<code>ClassLoader.getSystemClassLoader()</code>, in that order. If any of them cannot locate |
| * the specified class, an <code>UnknownClassException</code> is thrown (our RuntimeException equivalent of |
| * the JRE's <code>ClassNotFoundException</code>. |
| * |
| * @param fqcn the fully qualified class name to load |
| * @return the located class |
| * @throws UnknownClassException if the class cannot be found. |
| */ |
| public static Class forName(String fqcn) throws UnknownClassException { |
| Class clazz = null; |
| ClassLoader cl = Thread.currentThread().getContextClassLoader(); |
| if (cl != null) { |
| try { |
| clazz = cl.loadClass(fqcn); |
| } catch (ClassNotFoundException e) { |
| if (log.isTraceEnabled()) { |
| log.trace("Unable to load class named [" + fqcn + |
| "] from the thread context ClassLoader. Trying the current ClassLoader..."); |
| } |
| } |
| } |
| if (clazz == null) { |
| cl = ClassUtils.class.getClassLoader(); |
| try { |
| clazz = cl.loadClass(fqcn); |
| } catch (ClassNotFoundException e1) { |
| if (log.isTraceEnabled()) { |
| log.trace("Unable to load class named [" + fqcn + "] from the current ClassLoader. " + |
| "Trying the system/application ClassLoader..."); |
| } |
| cl = ClassLoader.getSystemClassLoader(); |
| try { |
| clazz = cl.loadClass(fqcn); |
| } catch (ClassNotFoundException ignored) { |
| if (log.isTraceEnabled()) { |
| log.trace("Unable to load class named [" + fqcn + "] from the " + |
| "system/application ClassLoader."); |
| } |
| } |
| } |
| } |
| |
| if (clazz == null) { |
| String msg = "Unable to load class named [" + fqcn + "] from the thread context, current, or " + |
| "system/application ClassLoaders. All heuristics have been exausted. Class could not be found."; |
| throw new UnknownClassException(msg); |
| } |
| return clazz; |
| } |
| |
| public static boolean isAvailable(String fullyQualifiedClassName) { |
| try { |
| forName(fullyQualifiedClassName); |
| return true; |
| } catch (UnknownClassException e) { |
| return false; |
| } |
| } |
| |
| public static Object newInstance(String fqcn) { |
| return newInstance(forName(fqcn)); |
| } |
| |
| public static Object newInstance(String fqcn, Object... args) { |
| return newInstance(forName(fqcn), args); |
| } |
| |
| public static Object newInstance(Class clazz) { |
| if (clazz == null) { |
| String msg = "Class method parameter cannot be null."; |
| throw new IllegalArgumentException(msg); |
| } |
| try { |
| return clazz.newInstance(); |
| } catch (Exception e) { |
| throw new org.ki.util.InstantiationException("Unable to instantiate class [" + clazz.getName() + "]", e); |
| } |
| } |
| |
| public static Object newInstance(Class clazz, Object... args) { |
| Class[] argTypes = new Class[args.length]; |
| for (int i = 0; i < args.length; i++) { |
| argTypes[i] = args[i].getClass(); |
| } |
| Constructor ctor = getConstructor(clazz, argTypes); |
| return instantiate(ctor, args); |
| } |
| |
| public static Constructor getConstructor(Class clazz, Class... argTypes) { |
| try { |
| return clazz.getConstructor(argTypes); |
| } catch (NoSuchMethodException e) { |
| throw new IllegalStateException(e); |
| } |
| |
| } |
| |
| public static Object instantiate(Constructor ctor, Object... args) { |
| try { |
| return ctor.newInstance(args); |
| } catch (Exception e) { |
| String msg = "Unable to instantiate Permission instance with constructor [" + ctor + "]"; |
| throw new org.ki.util.InstantiationException(msg, e); |
| } |
| } |
| |
| |
| } |