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Diffstat (limited to 'sdnr/wt/odlux/core/model/src/main/java/com/opensymphony/xwork2/util/ClassLoaderUtil.java')
| -rw-r--r-- | sdnr/wt/odlux/core/model/src/main/java/com/opensymphony/xwork2/util/ClassLoaderUtil.java | 235 |
1 files changed, 235 insertions, 0 deletions
diff --git a/sdnr/wt/odlux/core/model/src/main/java/com/opensymphony/xwork2/util/ClassLoaderUtil.java b/sdnr/wt/odlux/core/model/src/main/java/com/opensymphony/xwork2/util/ClassLoaderUtil.java new file mode 100644 index 000000000..10705b0ea --- /dev/null +++ b/sdnr/wt/odlux/core/model/src/main/java/com/opensymphony/xwork2/util/ClassLoaderUtil.java @@ -0,0 +1,235 @@ +/* + * Copyright 2002-2003,2009 The Apache Software Foundation. + * + * 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 com.opensymphony.xwork2.util; + +import java.io.IOException; +import java.io.InputStream; +import java.net.URL; +import java.util.*; + + +/** + * This class is extremely useful for loading resources and classes in a fault tolerant manner + * that works across different applications servers. + * + * It has come out of many months of frustrating use of multiple application servers at Atlassian, + * please don't change things unless you're sure they're not going to break in one server or another! + * + * It was brought in from oscore trunk revision 147. + * + * @author $Author$ + * @version $Revision$ + */ +public class ClassLoaderUtil { + //~ Methods //////////////////////////////////////////////////////////////// + + /** + * Load all resources with a given name, potentially aggregating all results + * from the searched classloaders. If no results are found, the resource name + * is prepended by '/' and tried again. + * + * This method will try to load the resources using the following methods (in order): + * <ul> + * <li>From Thread.currentThread().getContextClassLoader() + * <li>From ClassLoaderUtil.class.getClassLoader() + * <li>callingClass.getClassLoader() + * </ul> + * + * @param resourceName The name of the resources to load + * @param callingClass The Class object of the calling object + */ + public static Iterator<URL> getResources(String resourceName, Class callingClass, boolean aggregate) throws IOException { + + AggregateIterator<URL> iterator = new AggregateIterator<URL>(); + + iterator.addEnumeration(Thread.currentThread().getContextClassLoader().getResources(resourceName)); + + if (!iterator.hasNext() || aggregate) { + iterator.addEnumeration(ClassLoaderUtil.class.getClassLoader().getResources(resourceName)); + } + + if (!iterator.hasNext() || aggregate) { + ClassLoader cl = callingClass.getClassLoader(); + + if (cl != null) { + iterator.addEnumeration(cl.getResources(resourceName)); + } + } + + if (!iterator.hasNext() && (resourceName != null) && ((resourceName.length() == 0) || (resourceName.charAt(0) != '/'))) { + return getResources('/' + resourceName, callingClass, aggregate); + } + + return iterator; + } + + /** + * Load a given resource. + * + * This method will try to load the resource using the following methods (in order): + * <ul> + * <li>From Thread.currentThread().getContextClassLoader() + * <li>From ClassLoaderUtil.class.getClassLoader() + * <li>callingClass.getClassLoader() + * </ul> + * + * @param resourceName The name IllegalStateException("Unable to call ")of the resource to load + * @param callingClass The Class object of the calling object + */ + public static URL getResource(String resourceName, Class callingClass) { + URL url = Thread.currentThread().getContextClassLoader().getResource(resourceName); + + if (url == null) { + url = ClassLoaderUtil.class.getClassLoader().getResource(resourceName); + } + + if (url == null) { + ClassLoader cl = callingClass.getClassLoader(); + + if (cl != null) { + url = cl.getResource(resourceName); + } + } + + if ((url == null) && (resourceName != null) && ((resourceName.length() == 0) || (resourceName.charAt(0) != '/'))) { + return getResource('/' + resourceName, callingClass); + } + + return url; + } + + /** + * This is a convenience method to load a resource as a stream. + * + * The algorithm used to find the resource is given in getResource() + * + * @param resourceName The name of the resource to load + * @param callingClass The Class object of the calling object + */ + public static InputStream getResourceAsStream(String resourceName, Class callingClass) { + URL url = getResource(resourceName, callingClass); + + try { + return (url != null) ? url.openStream() : null; + } catch (IOException e) { + return null; + } + } + + /** + * Load a class with a given name. + * + * It will try to load the class in the following order: + * <ul> + * <li>From Thread.currentThread().getContextClassLoader() + * <li>Using the basic Class.forName() + * <li>From ClassLoaderUtil.class.getClassLoader() + * <li>From the callingClass.getClassLoader() + * </ul> + * + * @param className The name of the class to load + * @param callingClass The Class object of the calling object + * @throws ClassNotFoundException If the class cannot be found anywhere. + */ + public static Class loadClass(String className, Class callingClass) throws ClassNotFoundException { + try { + return Thread.currentThread().getContextClassLoader().loadClass(className); + } catch (ClassNotFoundException e) { + try { + return Class.forName(className); + } catch (ClassNotFoundException ex) { + try { + return ClassLoaderUtil.class.getClassLoader().loadClass(className); + } catch (ClassNotFoundException exc) { + return callingClass.getClassLoader().loadClass(className); + } + } + } + } + + /** + * Aggregates Enumeration instances into one iterator and filters out duplicates. Always keeps one + * ahead of the enumerator to protect against returning duplicates. + */ + static class AggregateIterator<E> implements Iterator<E> { + + LinkedList<Enumeration<E>> enums = new LinkedList<Enumeration<E>>(); + Enumeration<E> cur = null; + E next = null; + Set<E> loaded = new HashSet<E>(); + + public AggregateIterator<E> addEnumeration(Enumeration<E> e) { + if (e.hasMoreElements()) { + if (cur == null) { + cur = e; + next = e.nextElement(); + loaded.add(next); + } else { + enums.add(e); + } + } + return this; + } + + public boolean hasNext() { + return (next != null); + } + + public E next() { + if (next != null) { + E prev = next; + next = loadNext(); + return prev; + } else { + throw new NoSuchElementException(); + } + } + + private Enumeration<E> determineCurrentEnumeration() { + if (cur != null && !cur.hasMoreElements()) { + if (enums.size() > 0) { + cur = enums.removeLast(); + } else { + cur = null; + } + } + return cur; + } + + private E loadNext() { + if (determineCurrentEnumeration() != null) { + E tmp = cur.nextElement(); + int loadedSize = loaded.size(); + while (loaded.contains(tmp)) { + tmp = loadNext(); + if (tmp == null || loaded.size() > loadedSize) { + break; + } + } + if (tmp != null) { + loaded.add(tmp); + } + return tmp; + } + return null; + + } + + public void remove() { + throw new UnsupportedOperationException(); + } + } +}
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