| /* |
| * 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.apache.cocoon.jnet; |
| |
| import java.lang.reflect.Field; |
| import java.lang.reflect.Modifier; |
| import java.net.URL; |
| import java.net.URLStreamHandler; |
| import java.net.URLStreamHandlerFactory; |
| |
| /** |
| * The installer is a general purpose class to install an own {@link URLStreamHandlerFactory} in any environment. |
| */ |
| public class URLStreamHandlerFactoryInstaller { |
| |
| public static void setURLStreamHandlerFactory(URLStreamHandlerFactory factory) throws Exception { |
| try { |
| // if we can set the factory, its the first! |
| URL.setURLStreamHandlerFactory(new ParentableURLStreamHandlerFactory(factory, null)); |
| } catch (Error err) { |
| ParentableURLStreamHandlerFactory currentFactory = getCurrentFactory(); |
| setCurrentFactory(new ParentableURLStreamHandlerFactory(factory, currentFactory)); |
| } |
| } |
| |
| private static ParentableURLStreamHandlerFactory getCurrentFactory() throws Exception { |
| Field factoryField = getFactoryField(); |
| |
| URLStreamHandlerFactory currentFactory = (URLStreamHandlerFactory) factoryField.get(null); |
| if (currentFactory instanceof ParentableURLStreamHandlerFactory) { |
| return (ParentableURLStreamHandlerFactory) currentFactory; |
| } |
| |
| return new ParentableURLStreamHandlerFactory(currentFactory, null); |
| } |
| |
| private static Field getFactoryField() throws Exception { |
| // let's use reflection to get the field holding the factory |
| final Field[] fields = URL.class.getDeclaredFields(); |
| |
| for (int i = 0; i < fields.length; i++) { |
| Field current = fields[i]; |
| if (Modifier.isStatic(current.getModifiers()) && current.getType().equals(URLStreamHandlerFactory.class)) { |
| current.setAccessible(true); |
| return current; |
| } |
| } |
| |
| throw new Exception("Unable to detect static field in the URL class for the URLStreamHandlerFactory." |
| + " Please report this error together with your exact environment to the Apache Excalibur project."); |
| } |
| |
| private static void setCurrentFactory(ParentableURLStreamHandlerFactory parentableURLStreamHandlerFactory) throws Exception { |
| Field factoryField = getFactoryField(); |
| factoryField.set(null, parentableURLStreamHandlerFactory); |
| } |
| |
| private static class ParentableURLStreamHandlerFactory implements URLStreamHandlerFactory { |
| |
| private final URLStreamHandlerFactory factory; |
| private final ParentableURLStreamHandlerFactory parent; |
| |
| public ParentableURLStreamHandlerFactory(URLStreamHandlerFactory factory, ParentableURLStreamHandlerFactory parent) { |
| super(); |
| this.parent = parent; |
| this.factory = factory; |
| } |
| |
| public URLStreamHandler createURLStreamHandler(String protocol) { |
| URLStreamHandler handler = this.factory.createURLStreamHandler(protocol); |
| |
| if (handler == null && this.parent != null) { |
| handler = this.parent.createURLStreamHandler(protocol); |
| } |
| |
| return handler; |
| } |
| } |
| } |