1 /*
2 * Copyright (c) 2015, 2017, 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.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 import java.io.*;
26 import java.lang.reflect.*;
27 import java.util.jar.*;
28
29 public class Util {
30 /**
31 * Invoke the loader.defineClass() class method to define the class stored in clsFile,
32 * with the following modification:
33 * <ul>
34 * <li> All ASCII strings in the class file bytes that matches fromString will be replaced with toString.
35 * NOTE: the two strings must be the exact same length.
36 * </ul>
37 */
38 public static Class defineModifiedClass(ClassLoader loader, File clsFile, String fromString, String toString)
39 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
40 InvocationTargetException
41 {
42 DataInputStream dis = new DataInputStream(new FileInputStream(clsFile));
43 byte[] buff = new byte[(int)clsFile.length()];
44 dis.readFully(buff);
45 replace(buff, fromString, toString);
46
47 System.out.println("Loading from: " + clsFile + " (" + buff.length + " bytes)");
48
49 Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass",
50 buff.getClass(), int.class, int.class);
51 defineClass.setAccessible(true);
52
53 // We directly call into ClassLoader.defineClass() to define the "Super" class. Also,
54 // rewrite its classfile so that it returns ___yyy___ instead of ___xxx___. Changing the
55 // classfile will guarantee that this class will NOT be loaded from the CDS archive.
56 Class cls = (Class)defineClass.invoke(loader, buff, new Integer(0), new Integer(buff.length));
57 System.out.println("Loaded : " + cls);
58
59 return cls;
60 }
61
62 /**
63 * @return the number of occurrences of the <code>from</code> string that
64 * have been replaced.
65 */
66 public static int replace(byte buff[], String from, String to) {
67 if (to.length() != from.length()) {
68 throw new RuntimeException("bad strings");
69 }
70 byte f[] = asciibytes(from);
71 byte t[] = asciibytes(to);
72 byte f0 = f[0];
73
74 int numReplaced = 0;
75 int max = buff.length - f.length;
76 for (int i=0; i<max; ) {
77 if (buff[i] == f0 && replace(buff, f, t, i)) {
78 i += f.length;
79 numReplaced ++;
80 } else {
81 i++;
82 }
83 }
84 return numReplaced;
85 }
86
87 public static boolean replace(byte buff[], byte f[], byte t[], int i) {
88 for (int x=0; x<f.length; x++) {
89 if (buff[x+i] != f[x]) {
90 return false;
91 }
92 }
93 for (int x=0; x<f.length; x++) {
94 buff[x+i] = t[x];
95 }
96 return true;
97 }
98
99 static byte[] asciibytes(String s) {
100 byte b[] = new byte[s.length()];
101 for (int i=0; i<b.length; i++) {
102 b[i] = (byte)s.charAt(i);
103 }
104 return b;
105 }
106
107 public static Class defineClassFromJAR(ClassLoader loader, File jarFile, String className)
108 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
109 InvocationTargetException {
110 return defineClassFromJAR(loader, jarFile, className, null, null);
111 }
112
113 /**
114 * Invoke the loader.defineClass() class method to define the named class stored in a JAR file.
115 *
116 * If a class exists both in the classpath, as well as in the list of URLs of a URLClassLoader,
117 * by default, the URLClassLoader will not define the class, and instead will delegate to the
118 * app loader. This method is an easy way to force the class to be defined by the URLClassLoader.
119 *
120 * Optionally, you can modify the contents of the classfile buffer. See comments in
121 * defineModifiedClass.
122 */
123 public static Class defineClassFromJAR(ClassLoader loader, File jarFile, String className,
124 String fromString, String toString)
125 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
126 InvocationTargetException
127 {
128 byte[] buff = getClassFileFromJar(jarFile, className);
129
130 if (fromString != null) {
131 replace(buff, fromString, toString);
132 }
133
134 //System.out.println("Loading from: " + ent + " (" + buff.length + " bytes)");
135
136 Method defineClass = ClassLoader.class.getDeclaredMethod("defineClass",
137 buff.getClass(), int.class, int.class);
138 defineClass.setAccessible(true);
139 Class cls = (Class)defineClass.invoke(loader, buff, new Integer(0), new Integer(buff.length));
140
141 //System.out.println("Loaded : " + cls);
142 return cls;
143 }
144
145 public static byte[] getClassFileFromJar(File jarFile, String className) throws FileNotFoundException, IOException {
146 JarFile jf = new JarFile(jarFile);
147 JarEntry ent = jf.getJarEntry(className.replace('.', '/') + ".class");
148
149 DataInputStream dis = new DataInputStream(jf.getInputStream(ent));
150 byte[] buff = new byte[(int)ent.getSize()];
151 dis.readFully(buff);
152 dis.close();
153
154 return buff;
155 }
156 }