| 1 | /* This file is part of the project "Hilbert II" - http://www.qedeq.org |
| 2 | * |
| 3 | * Copyright 2000-2014, Michael Meyling <mime@qedeq.org>. |
| 4 | * |
| 5 | * "Hilbert II" is free software; you can redistribute |
| 6 | * it and/or modify it under the terms of the GNU General Public |
| 7 | * License as published by the Free Software Foundation; either |
| 8 | * version 2 of the License, or (at your option) any later version. |
| 9 | * |
| 10 | * This program is distributed in the hope that it will be useful, |
| 11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 13 | * GNU General Public License for more details. |
| 14 | */ |
| 15 | |
| 16 | package org.qedeq.base.io; |
| 17 | |
| 18 | import java.io.File; |
| 19 | import java.io.IOException; |
| 20 | import java.io.InputStream; |
| 21 | import java.lang.reflect.InvocationTargetException; |
| 22 | import java.lang.reflect.Method; |
| 23 | import java.net.URL; |
| 24 | |
| 25 | import org.qedeq.base.trace.Trace; |
| 26 | |
| 27 | |
| 28 | /** |
| 29 | * Utility methods for accessing classes and resources using an appropriate class loader. |
| 30 | * Adapted from org.apache.myfaces.trinidad.util.ClassLoaderUtils. |
| 31 | * |
| 32 | * @author Michael Meyling |
| 33 | */ |
| 34 | public final class ResourceLoaderUtility { |
| 35 | |
| 36 | /** This class. */ |
| 37 | private static final Class CLASS = ResourceLoaderUtility.class; |
| 38 | |
| 39 | /** |
| 40 | * Constructor, should never be called. |
| 41 | */ |
| 42 | private ResourceLoaderUtility() { |
| 43 | // don't call me |
| 44 | } |
| 45 | |
| 46 | /** |
| 47 | * Loads the class with the specified name. For Java 2 callers, the current thread's context |
| 48 | * class loader is preferred, falling back on the system class loader of the caller when the |
| 49 | * current thread's context is not set, or the caller is pre Java 2. |
| 50 | * |
| 51 | * @param name Name of class to load. |
| 52 | * @return The resulting <code>Class</code> object |
| 53 | * @exception ClassNotFoundException Class was not found. |
| 54 | */ |
| 55 | public static Class loadClass(final String name) throws ClassNotFoundException { |
| 56 | return loadClass(name, null); |
| 57 | } |
| 58 | |
| 59 | /** |
| 60 | * Locates the resource with the specified name. For Java 2 callers, the current thread's |
| 61 | * context class loader is preferred, falling back on the system class loader of the caller when |
| 62 | * the current thread's context is not set, or the caller is pre Java 2. |
| 63 | * |
| 64 | * @param name Resource name. |
| 65 | * @return Resulting <code>URL</code> object. Maybe <code>null</code>. |
| 66 | */ |
| 67 | public static URL getResourceUrl(final String name) { |
| 68 | return getResourceUrl(name, ResourceLoaderUtility.class.getClassLoader()); |
| 69 | } |
| 70 | |
| 71 | /** |
| 72 | * Locates the stream resource with the specified name. For Java 2 callers, the current thread's |
| 73 | * context class loader is preferred, falling back on the system class loader of the caller when |
| 74 | * the current thread's context is not set, or the caller is pre Java 2. |
| 75 | * |
| 76 | * @param name the name of the resource |
| 77 | * @return the resulting <code>InputStream</code> object |
| 78 | */ |
| 79 | public static InputStream getResourceAsStream(final String name) { |
| 80 | return getResourceAsStream(name, null); |
| 81 | } |
| 82 | |
| 83 | /** |
| 84 | * Loads the class with the specified name. For Java 2 callers, the current thread's context |
| 85 | * class loader is preferred, falling back on the class loader of the caller when the current |
| 86 | * thread's context is not set, or the caller is pre Java 2. If the callerClassLoader is null, |
| 87 | * then fall back on the system class loader. |
| 88 | * |
| 89 | * @param name the name of the class |
| 90 | * @param callerClassLoader the calling class loader context |
| 91 | * @return the resulting <code>Class</code> object |
| 92 | * @exception ClassNotFoundException if the class was not found |
| 93 | */ |
| 94 | public static Class loadClass(final String name, final ClassLoader callerClassLoader) |
| 95 | throws ClassNotFoundException { |
| 96 | Class clazz = null; |
| 97 | |
| 98 | try { |
| 99 | final ClassLoader loader = getContextClassLoader(); |
| 100 | |
| 101 | if (loader != null) { |
| 102 | clazz = loader.loadClass(name); |
| 103 | } |
| 104 | } catch (ClassNotFoundException e) { |
| 105 | // treat as though loader not set |
| 106 | } |
| 107 | |
| 108 | if (clazz == null) { |
| 109 | if (callerClassLoader != null) { |
| 110 | clazz = callerClassLoader.loadClass(name); |
| 111 | } else { |
| 112 | clazz = Class.forName(name); |
| 113 | } |
| 114 | } |
| 115 | |
| 116 | return clazz; |
| 117 | } |
| 118 | |
| 119 | /** |
| 120 | * Locates the resource with the specified name. For Java 2 callers, the current thread's |
| 121 | * context class loader is preferred, falling back on the class loader of the caller when the |
| 122 | * current thread's context is not set, or the caller is pre Java 2. If the callerClassLoader is |
| 123 | * null, then fall back on the system class loader. |
| 124 | * |
| 125 | * @param name the name of the resource |
| 126 | * @param callerClassLoader the calling class loader context |
| 127 | * @return the resulting <code>URL</code> object |
| 128 | */ |
| 129 | public static URL getResourceUrl(final String name, final ClassLoader callerClassLoader) { |
| 130 | checkResourceName(name); |
| 131 | |
| 132 | URL url = null; |
| 133 | |
| 134 | final ClassLoader loader = getContextClassLoader(); |
| 135 | |
| 136 | if (loader != null) { |
| 137 | url = loader.getResource(name); |
| 138 | } |
| 139 | |
| 140 | if (url == null) { |
| 141 | // no success, now we try the given class loader |
| 142 | if (callerClassLoader != null) { |
| 143 | url = callerClassLoader.getResource(name); |
| 144 | } else { |
| 145 | // last try: get resource via classpath |
| 146 | url = ClassLoader.getSystemResource(name); |
| 147 | } |
| 148 | } |
| 149 | return url; |
| 150 | } |
| 151 | |
| 152 | /** |
| 153 | * Locates the resource stream with the specified name. For Java 2 callers, the current thread's |
| 154 | * context class loader is preferred, falling back on the class loader of the caller when the |
| 155 | * current thread's context is not set, or the caller is pre Java 2. If the callerClassLoader is |
| 156 | * null, then fall back on the system class loader. |
| 157 | * |
| 158 | * @param name the name of the resource |
| 159 | * @param callerClassLoader the calling class loader context |
| 160 | * @return the resulting <code>InputStream</code> object |
| 161 | */ |
| 162 | public static InputStream getResourceAsStream(final String name, |
| 163 | final ClassLoader callerClassLoader) { |
| 164 | checkResourceName(name); |
| 165 | |
| 166 | InputStream stream = null; |
| 167 | |
| 168 | final ClassLoader loader = getContextClassLoader(); |
| 169 | |
| 170 | if (loader != null) { |
| 171 | stream = loader.getResourceAsStream(name); |
| 172 | } |
| 173 | if (stream == null) { |
| 174 | if (callerClassLoader != null) { |
| 175 | stream = callerClassLoader.getResourceAsStream(name); |
| 176 | } else { |
| 177 | stream = ClassLoader.getSystemResourceAsStream(name); |
| 178 | } |
| 179 | } |
| 180 | |
| 181 | return stream; |
| 182 | } |
| 183 | |
| 184 | /** |
| 185 | * Dynamically accesses the current context class loader. Returns <code>null</code> if there is |
| 186 | * no per-thread context class loader. Also if the JRE is below 1.2 or something else went wrong |
| 187 | * the method returns <code>null</code>. |
| 188 | * |
| 189 | * @return ClassLoader. |
| 190 | */ |
| 191 | public static ClassLoader getContextClassLoader() { |
| 192 | try { |
| 193 | final Method method = Thread.class.getMethod("getContextClassLoader", null); |
| 194 | return (ClassLoader) method.invoke(Thread.currentThread(), null); |
| 195 | } catch (RuntimeException e) { |
| 196 | return null; |
| 197 | } catch (IllegalAccessException e) { |
| 198 | return null; |
| 199 | } catch (InvocationTargetException e) { |
| 200 | return null; |
| 201 | } catch (NoSuchMethodException e) { |
| 202 | return null; |
| 203 | } |
| 204 | } |
| 205 | |
| 206 | private static void checkResourceName(final String name) { |
| 207 | if ((name != null) && name.startsWith("/")) { |
| 208 | Trace.info(CLASS, "ClassLoaderUtility", "checkResourceName", |
| 209 | "resource name not portable: " + name); |
| 210 | |
| 211 | } |
| 212 | } |
| 213 | |
| 214 | /** |
| 215 | * Get resource file. The resource is located within the file system if it exists already. |
| 216 | * If not it is loaded as resource and then saved as a file. |
| 217 | * |
| 218 | * @param startDirectory Start looking from this directory. |
| 219 | * @param resourceDirectoryName Within this directory |
| 220 | * (relative to <code>startDirectory</code>). |
| 221 | * @param resourceName Look for this resource file. |
| 222 | * @return Resource file. |
| 223 | */ |
| 224 | public static File getResourceFile(final File startDirectory, |
| 225 | final String resourceDirectoryName, final String resourceName) { |
| 226 | final File resourceDir = new File(startDirectory, resourceDirectoryName); |
| 227 | final File resource = new File(resourceDir, resourceName); |
| 228 | if (!resource.exists()) { |
| 229 | final URL url = getResourceUrl(resourceDirectoryName + "/" + resourceName); |
| 230 | if (url == null) { |
| 231 | Trace.info(ResourceLoaderUtility.class, "getResourceUrlAndMakeLocalCopy", |
| 232 | "URL not found for: " + resourceDirectoryName + "/" + resourceName); |
| 233 | return null; |
| 234 | } |
| 235 | try { |
| 236 | if (!resourceDir.exists()) { |
| 237 | if (!resourceDir.mkdirs()) { |
| 238 | Trace.info(ResourceLoaderUtility.class, "getResourceUrlAndMakeLocalCopy", |
| 239 | "creation failed: " + resourceDir); |
| 240 | } |
| 241 | } |
| 242 | IoUtility.saveFile(url, resource); |
| 243 | } catch (IOException e) { |
| 244 | Trace.fatal(ResourceLoaderUtility.class, "getResourceUrlAndMakeLocalCopy", |
| 245 | "resource can not be saved", e); |
| 246 | } |
| 247 | } |
| 248 | return resource; |
| 249 | } |
| 250 | |
| 251 | } |