001/* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache license, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the license for the specific language governing permissions and 015 * limitations under the license. 016 */ 017package org.apache.logging.log4j.util; 018 019import java.lang.reflect.Method; 020import java.util.Stack; 021 022import org.apache.logging.log4j.Logger; 023import org.apache.logging.log4j.status.StatusLogger; 024 025/** 026 * <em>Consider this class private.</em> Provides various methods to determine the caller class. <h3>Background</h3> 027 * <p> 028 * This method, available only in the Oracle/Sun/OpenJDK implementations of the Java Virtual Machine, is a much more 029 * efficient mechanism for determining the {@link Class} of the caller of a particular method. When it is not available, 030 * a {@link SecurityManager} is the second-best option. When this is also not possible, the {@code StackTraceElement[]} 031 * returned by {@link Throwable#getStackTrace()} must be used, and its {@code String} class name converted to a 032 * {@code Class} using the slow {@link Class#forName} (which can add an extra microsecond or more for each invocation 033 * depending on the runtime ClassLoader hierarchy). 034 * </p> 035 * <p> 036 * During Java 8 development, the {@code sun.reflect.Reflection.getCallerClass(int)} was removed from OpenJDK, and this 037 * change was back-ported to Java 7 in version 1.7.0_25 which changed the behavior of the call and caused it to be off 038 * by one stack frame. This turned out to be beneficial for the survival of this API as the change broke hundreds of 039 * libraries and frameworks relying on the API which brought much more attention to the intended API removal. 040 * </p> 041 * <p> 042 * After much community backlash, the JDK team agreed to restore {@code getCallerClass(int)} and keep its existing 043 * behavior for the rest of Java 7. However, the method is deprecated in Java 8, and current Java 9 development has not 044 * addressed this API. Therefore, the functionality of this class cannot be relied upon for all future versions of Java. 045 * It does, however, work just fine in Sun JDK 1.6, OpenJDK 1.6, Oracle/OpenJDK 1.7, and Oracle/OpenJDK 1.8. Other Java 046 * environments may fall back to using {@link Throwable#getStackTrace()} which is significantly slower due to 047 * examination of every virtual frame of execution. 048 * </p> 049 */ 050public final class ReflectionUtil { 051 // Checkstyle Suppress: the lower-case 'u' ticks off CheckStyle... 052 // CHECKSTYLE:OFF 053 static final int JDK_7u25_OFFSET; 054 // CHECKSTYLE:OFF 055 056 private static final Logger LOGGER = StatusLogger.getLogger(); 057 private static final boolean SUN_REFLECTION_SUPPORTED; 058 private static final Method GET_CALLER_CLASS; 059 private static final PrivateSecurityManager SECURITY_MANAGER; 060 061 static { 062 Method getCallerClass; 063 int java7u25CompensationOffset = 0; 064 try { 065 final Class<?> sunReflectionClass = LoaderUtil.loadClass("sun.reflect.Reflection"); 066 getCallerClass = sunReflectionClass.getDeclaredMethod("getCallerClass", int.class); 067 Object o = getCallerClass.invoke(null, 0); 068 final Object test1 = getCallerClass.invoke(null, 0); 069 if (o == null || o != sunReflectionClass) { 070 LOGGER.warn("Unexpected return value from Reflection.getCallerClass(): {}", test1); 071 getCallerClass = null; 072 java7u25CompensationOffset = -1; 073 } else { 074 o = getCallerClass.invoke(null, 1); 075 if (o == sunReflectionClass) { 076 LOGGER.warn("You are using Java 1.7.0_25 which has a broken implementation of " 077 + "Reflection.getCallerClass."); 078 LOGGER.warn("You should upgrade to at least Java 1.7.0_40 or later."); 079 LOGGER.debug("Using stack depth compensation offset of 1 due to Java 7u25."); 080 java7u25CompensationOffset = 1; 081 } 082 } 083 } catch (final Exception e) { 084 LOGGER.info("sun.reflect.Reflection.getCallerClass is not supported. " 085 + "ReflectionUtil.getCallerClass will be much slower due to this.", e); 086 getCallerClass = null; 087 java7u25CompensationOffset = -1; 088 } 089 090 SUN_REFLECTION_SUPPORTED = getCallerClass != null; 091 GET_CALLER_CLASS = getCallerClass; 092 JDK_7u25_OFFSET = java7u25CompensationOffset; 093 094 PrivateSecurityManager psm; 095 try { 096 final SecurityManager sm = System.getSecurityManager(); 097 if (sm != null) { 098 sm.checkPermission(new RuntimePermission("createSecurityManager")); 099 } 100 psm = new PrivateSecurityManager(); 101 } catch (final SecurityException ignored) { 102 LOGGER.debug("Not allowed to create SecurityManager. " 103 + "Falling back to slowest ReflectionUtil implementation."); 104 psm = null; 105 } 106 SECURITY_MANAGER = psm; 107 } 108 109 private ReflectionUtil() { 110 } 111 112 public static boolean supportsFastReflection() { 113 return SUN_REFLECTION_SUPPORTED; 114 } 115 116 // TODO: return Object.class instead of null (though it will have a null ClassLoader) 117 // (MS) I believe this would work without any modifications elsewhere, but I could be wrong 118 119 // migrated from ReflectiveCallerClassUtility 120 public static Class<?> getCallerClass(final int depth) { 121 if (depth < 0) { 122 throw new IndexOutOfBoundsException(Integer.toString(depth)); 123 } 124 // note that we need to add 1 to the depth value to compensate for this method, but not for the Method.invoke 125 // since Reflection.getCallerClass ignores the call to Method.invoke() 126 if (supportsFastReflection()) { 127 try { 128 return (Class<?>) GET_CALLER_CLASS.invoke(null, depth + 1 + JDK_7u25_OFFSET); 129 } catch (final Exception e) { 130 // theoretically this could happen if the caller class were native code 131 LOGGER.error("Error in ReflectionUtil.getCallerClass({}).", depth, e); 132 // TODO: return Object.class 133 return null; 134 } 135 } 136 // TODO: SecurityManager-based version? 137 // slower fallback method using stack trace 138 final StackTraceElement element = getEquivalentStackTraceElement(depth + 1); 139 try { 140 return LoaderUtil.loadClass(element.getClassName()); 141 } catch (final ClassNotFoundException e) { 142 LOGGER.error("Could not find class in ReflectionUtil.getCallerClass({}).", depth, e); 143 } 144 // TODO: return Object.class 145 return null; 146 } 147 148 static StackTraceElement getEquivalentStackTraceElement(final int depth) { 149 // (MS) I tested the difference between using Throwable.getStackTrace() and Thread.getStackTrace(), and 150 // the version using Throwable was surprisingly faster! at least on Java 1.8. See ReflectionBenchmark. 151 final StackTraceElement[] elements = new Throwable().getStackTrace(); 152 int i = 0; 153 for (final StackTraceElement element : elements) { 154 if (isValid(element)) { 155 if (i == depth) { 156 return element; 157 } 158 ++i; 159 } 160 } 161 LOGGER.error("Could not find an appropriate StackTraceElement at index {}", depth); 162 throw new IndexOutOfBoundsException(Integer.toString(depth)); 163 } 164 165 private static boolean isValid(final StackTraceElement element) { 166 // ignore native methods (oftentimes are repeated frames) 167 if (element.isNativeMethod()) { 168 return false; 169 } 170 final String cn = element.getClassName(); 171 // ignore OpenJDK internal classes involved with reflective invocation 172 if (cn.startsWith("sun.reflect.")) { 173 return false; 174 } 175 final String mn = element.getMethodName(); 176 // ignore use of reflection including: 177 // Method.invoke 178 // InvocationHandler.invoke 179 // Constructor.newInstance 180 if (cn.startsWith("java.lang.reflect.") && (mn.equals("invoke") || mn.equals("newInstance"))) { 181 return false; 182 } 183 // ignore Class.newInstance 184 if (cn.equals("java.lang.Class") && mn.equals("newInstance")) { 185 return false; 186 } 187 // ignore use of Java 1.7+ MethodHandle.invokeFoo() methods 188 if (cn.equals("java.lang.invoke.MethodHandle") && mn.startsWith("invoke")) { 189 return false; 190 } 191 // any others? 192 return true; 193 } 194 195 // migrated from ClassLoaderContextSelector 196 public static Class<?> getCallerClass(final String fqcn) { 197 return getCallerClass(fqcn, Strings.EMPTY); 198 } 199 200 // migrated from Log4jLoggerFactory 201 public static Class<?> getCallerClass(final String fqcn, final String pkg) { 202 if (supportsFastReflection()) { 203 boolean next = false; 204 Class<?> clazz; 205 for (int i = 2; null != (clazz = getCallerClass(i)); i++) { 206 if (fqcn.equals(clazz.getName())) { 207 next = true; 208 continue; 209 } 210 if (next && clazz.getName().startsWith(pkg)) { 211 return clazz; 212 } 213 } 214 // TODO: return Object.class 215 return null; 216 } 217 if (SECURITY_MANAGER != null) { 218 return SECURITY_MANAGER.getCallerClass(fqcn, pkg); 219 } 220 try { 221 return LoaderUtil.loadClass(getCallerClassName(fqcn, pkg, new Throwable().getStackTrace())); 222 } catch (final ClassNotFoundException ignored) { 223 // no problem really 224 } 225 // TODO: return Object.class 226 return null; 227 } 228 229 // added for use in LoggerAdapter implementations mainly 230 public static Class<?> getCallerClass(final Class<?> anchor) { 231 if (supportsFastReflection()) { 232 boolean next = false; 233 Class<?> clazz; 234 for (int i = 2; null != (clazz = getCallerClass(i)); i++) { 235 if (anchor.equals(clazz)) { 236 next = true; 237 continue; 238 } 239 if (next) { 240 return clazz; 241 } 242 } 243 return Object.class; 244 } 245 if (SECURITY_MANAGER != null) { 246 return SECURITY_MANAGER.getCallerClass(anchor); 247 } 248 try { 249 return LoaderUtil.loadClass(getCallerClassName(anchor.getName(), Strings.EMPTY, 250 new Throwable().getStackTrace())); 251 } catch (final ClassNotFoundException ignored) { 252 // no problem really 253 } 254 return Object.class; 255 } 256 257 private static String getCallerClassName(final String fqcn, final String pkg, final StackTraceElement... elements) { 258 boolean next = false; 259 for (final StackTraceElement element : elements) { 260 final String className = element.getClassName(); 261 if (className.equals(fqcn)) { 262 next = true; 263 continue; 264 } 265 if (next && className.startsWith(pkg)) { 266 return className; 267 } 268 } 269 return Object.class.getName(); 270 } 271 272 // migrated from ThrowableProxy 273 public static Stack<Class<?>> getCurrentStackTrace() { 274 // benchmarks show that using the SecurityManager is much faster than looping through getCallerClass(int) 275 if (SECURITY_MANAGER != null) { 276 final Class<?>[] array = SECURITY_MANAGER.getClassContext(); 277 final Stack<Class<?>> classes = new Stack<>(); 278 classes.ensureCapacity(array.length); 279 for (final Class<?> clazz : array) { 280 classes.push(clazz); 281 } 282 return classes; 283 } 284 // slower version using getCallerClass where we cannot use a SecurityManager 285 if (supportsFastReflection()) { 286 final Stack<Class<?>> classes = new Stack<>(); 287 Class<?> clazz; 288 for (int i = 1; null != (clazz = getCallerClass(i)); i++) { 289 classes.push(clazz); 290 } 291 return classes; 292 } 293 return new Stack<>(); 294 } 295 296 /** 297 * 298 */ 299 static final class PrivateSecurityManager extends SecurityManager { 300 301 @Override 302 protected Class<?>[] getClassContext() { 303 return super.getClassContext(); 304 } 305 306 protected Class<?> getCallerClass(final String fqcn, final String pkg) { 307 boolean next = false; 308 for (final Class<?> clazz : getClassContext()) { 309 if (fqcn.equals(clazz.getName())) { 310 next = true; 311 continue; 312 } 313 if (next && clazz.getName().startsWith(pkg)) { 314 return clazz; 315 } 316 } 317 // TODO: return Object.class 318 return null; 319 } 320 321 protected Class<?> getCallerClass(final Class<?> anchor) { 322 boolean next = false; 323 for (final Class<?> clazz : getClassContext()) { 324 if (anchor.equals(clazz)) { 325 next = true; 326 continue; 327 } 328 if (next) { 329 return clazz; 330 } 331 } 332 return Object.class; 333 } 334 } 335}