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| 1 | /* | ||
| 2 | * Copyright (c) 2003, 2008, Oracle and/or its affiliates. All rights reserved. | ||
| 3 | * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | ||
| 4 | * | ||
| 5 | * This code is free software; you can redistribute it and/or modify it | ||
| 6 | * under the terms of the GNU General Public License version 2 only, as | ||
| 7 | * published by the Free Software Foundation. Oracle designates this | ||
| 8 | * particular file as subject to the "Classpath" exception as provided | ||
| 9 | * by Oracle in the LICENSE file that accompanied this code. | ||
| 10 | * | ||
| 11 | * This code is distributed in the hope that it will be useful, but WITHOUT | ||
| 12 | * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | ||
| 13 | * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | ||
| 14 | * version 2 for more details (a copy is included in the LICENSE file that | ||
| 15 | * accompanied this code). | ||
| 16 | * | ||
| 17 | * You should have received a copy of the GNU General Public License version | ||
| 18 | * 2 along with this work; if not, write to the Free Software Foundation, | ||
| 19 | * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | ||
| 20 | * | ||
| 21 | * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA | ||
| 22 | * or visit www.oracle.com if you need additional information or have any | ||
| 23 | * questions. | ||
| 24 | */ | ||
| 25 | |||
| 26 | package javax.management.remote.rmi; | ||
| 27 | |||
| 28 | import java.security.ProtectionDomain; | ||
| 29 | |||
| 30 | /** | ||
| 31 | <p>A class loader that only knows how to define a limited number | ||
| 32 | of classes, and load a limited number of other classes through | ||
| 33 | delegation to another loader. It is used to get around a problem | ||
| 34 | with Serialization, in particular as used by RMI (including | ||
| 35 | RMI/IIOP). The JMX Remote API defines exactly what class loader | ||
| 36 | must be used to deserialize arguments on the server, and return | ||
| 37 | values on the client. We communicate this class loader to RMI by | ||
| 38 | setting it as the context class loader. RMI uses the context | ||
| 39 | class loader to load classes as it deserializes, which is what we | ||
| 40 | want. However, before consulting the context class loader, it | ||
| 41 | looks up the call stack for a class with a non-null class loader, | ||
| 42 | and uses that if it finds one. So, in the standalone version of | ||
| 43 | javax.management.remote, if the class you're looking for is known | ||
| 44 | to the loader of jmxremote.jar (typically the system class loader) | ||
| 45 | then that loader will load it. This contradicts the class-loading | ||
| 46 | semantics required. | ||
| 47 | |||
| 48 | <p>We get around the problem by ensuring that the search up the | ||
| 49 | call stack will find a non-null class loader that doesn't load any | ||
| 50 | classes of interest, namely this one. So even though this loader | ||
| 51 | is indeed consulted during deserialization, it never finds the | ||
| 52 | class being deserialized. RMI then proceeds to use the context | ||
| 53 | class loader, as we require. | ||
| 54 | |||
| 55 | <p>This loader is constructed with the name and byte-code of one | ||
| 56 | or more classes that it defines, and a class-loader to which it | ||
| 57 | will delegate certain other classes required by that byte-code. | ||
| 58 | We construct the byte-code somewhat painstakingly, by compiling | ||
| 59 | the Java code directly, converting into a string, copying that | ||
| 60 | string into the class that needs this loader, and using the | ||
| 61 | stringToBytes method to convert it into the byte array. We | ||
| 62 | compile with -g:none because there's not much point in having | ||
| 63 | line-number information and the like in these directly-encoded | ||
| 64 | classes. | ||
| 65 | |||
| 66 | <p>The referencedClassNames should contain the names of all | ||
| 67 | classes that are referenced by the classes defined by this loader. | ||
| 68 | It is not necessary to include standard J2SE classes, however. | ||
| 69 | Here, a class is referenced if it is the superclass or a | ||
| 70 | superinterface of a defined class, or if it is the type of a | ||
| 71 | field, parameter, or return value. A class is not referenced if | ||
| 72 | it only appears in the throws clause of a method or constructor. | ||
| 73 | Of course, referencedClassNames should not contain any classes | ||
| 74 | that the user might want to deserialize, because the whole point | ||
| 75 | of this loader is that it does not find such classes. | ||
| 76 | */ | ||
| 77 | |||
| 78 | class NoCallStackClassLoader extends ClassLoader { | ||
| 79 | /** Simplified constructor when this loader only defines one class. */ | ||
| 80 | public NoCallStackClassLoader(String className, | ||
| 81 | byte[] byteCode, | ||
| 82 | String[] referencedClassNames, | ||
| 83 | ClassLoader referencedClassLoader, | ||
| 84 | ProtectionDomain protectionDomain) { | ||
| 85 | this(new String[] {className}, new byte[][] {byteCode}, | ||
| 86 | referencedClassNames, referencedClassLoader, protectionDomain); | ||
| 87 | } | ||
| 88 | |||
| 89 | public NoCallStackClassLoader(String[] classNames, | ||
| 90 | byte[][] byteCodes, | ||
| 91 | String[] referencedClassNames, | ||
| 92 | ClassLoader referencedClassLoader, | ||
| 93 | ProtectionDomain protectionDomain) { | ||
| 94 | super(null); | ||
| 95 | |||
| 96 | /* Validation. */ | ||
| 97 | if (classNames == null || classNames.length == 0 | ||
| 98 | || byteCodes == null || classNames.length != byteCodes.length | ||
| 99 | || referencedClassNames == null || protectionDomain == null) | ||
| 100 | throw new IllegalArgumentException(); | ||
| 101 | for (int i = 0; i < classNames.length; i++) { | ||
| 102 | if (classNames[i] == null || byteCodes[i] == null) | ||
| 103 | throw new IllegalArgumentException(); | ||
| 104 | } | ||
| 105 | for (int i = 0; i < referencedClassNames.length; i++) { | ||
| 106 | if (referencedClassNames[i] == null) | ||
| 107 | throw new IllegalArgumentException(); | ||
| 108 | } | ||
| 109 | |||
| 110 | this.classNames = classNames; | ||
| 111 | this.byteCodes = byteCodes; | ||
| 112 | this.referencedClassNames = referencedClassNames; | ||
| 113 | this.referencedClassLoader = referencedClassLoader; | ||
| 114 | this.protectionDomain = protectionDomain; | ||
| 115 | } | ||
| 116 | |||
| 117 | /* This method is called at most once per name. Define the name | ||
| 118 | * if it is one of the classes whose byte code we have, or | ||
| 119 | * delegate the load if it is one of the referenced classes. | ||
| 120 | */ | ||
| 121 | @Override | ||
| 122 | protected Class<?> findClass(String name) throws ClassNotFoundException { | ||
| 123 | for (int i = 0; i < classNames.length; i++) { | ||
| 124 | if (name.equals(classNames[i])) { | ||
| 125 | return defineClass(classNames[i], byteCodes[i], 0, | ||
| 126 | byteCodes[i].length, protectionDomain); | ||
| 127 | } | ||
| 128 | } | ||
| 129 | |||
| 130 | /* If the referencedClassLoader is null, it is the bootstrap | ||
| 131 | * class loader, and there's no point in delegating to it | ||
| 132 | * because it's already our parent class loader. | ||
| 133 | */ | ||
| 134 | if (referencedClassLoader != null) { | ||
| 135 | for (int i = 0; i < referencedClassNames.length; i++) { | ||
| 136 | if (name.equals(referencedClassNames[i])) | ||
| 137 | return referencedClassLoader.loadClass(name); | ||
| 138 | } | ||
| 139 | } | ||
| 140 | |||
| 141 | throw new ClassNotFoundException(name); | ||
| 142 | } | ||
| 143 | |||
| 144 | private final String[] classNames; | ||
| 145 | private final byte[][] byteCodes; | ||
| 146 | private final String[] referencedClassNames; | ||
| 147 | private final ClassLoader referencedClassLoader; | ||
| 148 | private final ProtectionDomain protectionDomain; | ||
| 149 | |||
| 150 | /** | ||
| 151 | * <p>Construct a <code>byte[]</code> using the characters of the | ||
| 152 | * given <code>String</code>. Only the low-order byte of each | ||
| 153 | * character is used. This method is useful to reduce the | ||
| 154 | * footprint of classes that include big byte arrays (e.g. the | ||
| 155 | * byte code of other classes), because a string takes up much | ||
| 156 | * less space in a class file than the byte code to initialize a | ||
| 157 | * <code>byte[]</code> with the same number of bytes.</p> | ||
| 158 | * | ||
| 159 | * <p>We use just one byte per character even though characters | ||
| 160 | * contain two bytes. The resultant output length is much the | ||
| 161 | * same: using one byte per character is shorter because it has | ||
| 162 | * more characters in the optimal 1-127 range but longer because | ||
| 163 | * it has more zero bytes (which are frequent, and are encoded as | ||
| 164 | * two bytes in classfile UTF-8). But one byte per character has | ||
| 165 | * two key advantages: (1) you can see the string constants, which | ||
| 166 | * is reassuring, (2) you don't need to know whether the class | ||
| 167 | * file length is odd.</p> | ||
| 168 | * | ||
| 169 | * <p>This method differs from {@link String#getBytes()} in that | ||
| 170 | * it does not use any encoding. So it is guaranteed that each | ||
| 171 | * byte of the result is numerically identical (mod 256) to the | ||
| 172 | * corresponding character of the input. | ||
| 173 | */ | ||
| 174 | public static byte[] stringToBytes(String s) { | ||
| 175 | final int slen = s.length(); | ||
| 176 | byte[] bytes = new byte[slen]; | ||
| 177 | for (int i = 0; i < slen; i++) | ||
| 178 | bytes[i] = (byte) s.charAt(i); | ||
| 179 | return bytes; | ||
| 180 | } | ||
| 181 | } | ||
| 182 | |||
| 183 | /* | ||
| 184 | |||
| 185 | You can use the following Emacs function to convert class files into | ||
| 186 | strings to be used by the stringToBytes method above. Select the | ||
| 187 | whole (defun...) with the mouse and type M-x eval-region, or save it | ||
| 188 | to a file and do M-x load-file. Then visit the *.class file and do | ||
| 189 | M-x class-string. | ||
| 190 | |||
| 191 | ;; class-string.el | ||
| 192 | ;; visit the *.class file with emacs, then invoke this function | ||
| 193 | |||
| 194 | (defun class-string () | ||
| 195 | "Construct a Java string whose bytes are the same as the current | ||
| 196 | buffer. The resultant string is put in a buffer called *string*, | ||
| 197 | possibly with a numeric suffix like <2>. From there it can be | ||
| 198 | insert-buffer'd into a Java program." | ||
| 199 | (interactive) | ||
| 200 | (let* ((s (buffer-string)) | ||
| 201 | (slen (length s)) | ||
| 202 | (i 0) | ||
| 203 | (buf (generate-new-buffer "*string*"))) | ||
| 204 | (set-buffer buf) | ||
| 205 | (insert "\"") | ||
| 206 | (while (< i slen) | ||
| 207 | (if (> (current-column) 61) | ||
| 208 | (insert "\"+\n\"")) | ||
| 209 | (let ((c (aref s i))) | ||
| 210 | (insert (cond | ||
| 211 | ((> c 126) (format "\\%o" c)) | ||
| 212 | ((= c ?\") "\\\"") | ||
| 213 | ((= c ?\\) "\\\\") | ||
| 214 | ((< c 33) | ||
| 215 | (let ((nextc (if (< (1+ i) slen) | ||
| 216 | (aref s (1+ i)) | ||
| 217 | ?\0))) | ||
| 218 | (cond | ||
| 219 | ((and (<= nextc ?7) (>= nextc ?0)) | ||
| 220 | (format "\\%03o" c)) | ||
| 221 | (t | ||
| 222 | (format "\\%o" c))))) | ||
| 223 | (t c)))) | ||
| 224 | (setq i (1+ i))) | ||
| 225 | (insert "\"") | ||
| 226 | (switch-to-buffer buf))) | ||
| 227 | |||
| 228 | Alternatively, the following class reads a class file and outputs a string | ||
| 229 | that can be used by the stringToBytes method above. | ||
| 230 | |||
| 231 | import java.io.File; | ||
| 232 | import java.io.FileInputStream; | ||
| 233 | import java.io.IOException; | ||
| 234 | |||
| 235 | public class BytesToString { | ||
| 236 | |||
| 237 | public static void main(String[] args) throws IOException { | ||
| 238 | File f = new File(args[0]); | ||
| 239 | int len = (int)f.length(); | ||
| 240 | byte[] classBytes = new byte[len]; | ||
| 241 | |||
| 242 | FileInputStream in = new FileInputStream(args[0]); | ||
| 243 | try { | ||
| 244 | int pos = 0; | ||
| 245 | for (;;) { | ||
| 246 | int n = in.read(classBytes, pos, (len-pos)); | ||
| 247 | if (n < 0) | ||
| 248 | throw new RuntimeException("class file changed??"); | ||
| 249 | pos += n; | ||
| 250 | if (pos >= n) | ||
| 251 | break; | ||
| 252 | } | ||
| 253 | } finally { | ||
| 254 | in.close(); | ||
| 255 | } | ||
| 256 | |||
| 257 | int pos = 0; | ||
| 258 | boolean lastWasOctal = false; | ||
| 259 | for (int i=0; i<len; i++) { | ||
| 260 | int value = classBytes[i]; | ||
| 261 | if (value < 0) | ||
| 262 | value += 256; | ||
| 263 | String s = null; | ||
| 264 | if (value == '\\') | ||
| 265 | s = "\\\\"; | ||
| 266 | else if (value == '\"') | ||
| 267 | s = "\\\""; | ||
| 268 | else { | ||
| 269 | if ((value >= 32 && value < 127) && ((!lastWasOctal || | ||
| 270 | (value < '0' || value > '7')))) { | ||
| 271 | s = Character.toString((char)value); | ||
| 272 | } | ||
| 273 | } | ||
| 274 | if (s == null) { | ||
| 275 | s = "\\" + Integer.toString(value, 8); | ||
| 276 | lastWasOctal = true; | ||
| 277 | } else { | ||
| 278 | lastWasOctal = false; | ||
| 279 | } | ||
| 280 | if (pos > 61) { | ||
| 281 | System.out.print("\""); | ||
| 282 | if (i<len) | ||
| 283 | System.out.print("+"); | ||
| 284 | System.out.println(); | ||
| 285 | pos = 0; | ||
| 286 | } | ||
| 287 | if (pos == 0) | ||
| 288 | System.out.print(" \""); | ||
| 289 | System.out.print(s); | ||
| 290 | pos += s.length(); | ||
| 291 | } | ||
| 292 | System.out.println("\""); | ||
| 293 | } | ||
| 294 | } | ||
| 295 | |||
| 296 | */ | ||