1 /*
2 * Copyright (c) 2015, 2019, 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.invoke.MethodHandles;
27 import java.lang.invoke.MethodHandles.Lookup;
28 import java.lang.reflect.*;
29 import java.util.jar.*;
30
31 public class Util {
32 /**
33 * Define the class as stored in clsFile, in the same loader as peerClass,
34 * with the following modification:
35 * <ul>
36 * <li> All ASCII strings in the class file bytes that matches fromString will be replaced with toString.
37 * NOTE: the two strings must be the exact same length.
38 * </ul>
39 */
40 public static Class<?> defineModifiedClass(Class<?> peerClass, File clsFile, String fromString, String toString)
41 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
42 InvocationTargetException
43 {
44 try (DataInputStream dis = new DataInputStream(new FileInputStream(clsFile))) {
45 byte[] buff = new byte[(int)clsFile.length()];
46 dis.readFully(buff);
47 replace(buff, fromString, toString);
48
49 System.out.println("Loading from: " + clsFile + " (" + buff.length + " bytes)");
50
51
52 // We directly call into Lookup.defineClass() to define the "Super" class. Also,
53 // rewrite its classfile so that it returns ___yyy___ instead of ___xxx___. Changing the
54 // classfile will guarantee that this class will NOT be loaded from the CDS archive.
55 Lookup lookup = MethodHandles.privateLookupIn(peerClass, MethodHandles.lookup());
56 Class<?> cls = lookup.defineClass(buff);
57 System.out.println("Loaded : " + cls);
58
59 return cls;
60 }
61 }
62
63 /**
64 * @return the number of occurrences of the <code>from</code> string that
65 * have been replaced.
66 */
67 public static int replace(byte buff[], String from, String to) {
68 if (to.length() != from.length()) {
69 throw new RuntimeException("bad strings");
70 }
71 byte f[] = asciibytes(from);
72 byte t[] = asciibytes(to);
73 byte f0 = f[0];
74
75 int numReplaced = 0;
76 int max = buff.length - f.length;
77 for (int i=0; i<max; ) {
78 if (buff[i] == f0 && replace(buff, f, t, i)) {
79 i += f.length;
80 numReplaced ++;
81 } else {
82 i++;
83 }
84 }
85 return numReplaced;
86 }
87
88 public static boolean replace(byte buff[], byte f[], byte t[], int i) {
89 for (int x=0; x<f.length; x++) {
90 if (buff[x+i] != f[x]) {
91 return false;
92 }
93 }
94 for (int x=0; x<f.length; x++) {
95 buff[x+i] = t[x];
96 }
97 return true;
98 }
99
100 static byte[] asciibytes(String s) {
101 byte b[] = new byte[s.length()];
102 for (int i=0; i<b.length; i++) {
103 b[i] = (byte)s.charAt(i);
104 }
105 return b;
106 }
107
108 public static Class defineClassFromJAR(Class<?> peerClass, File jarFile, String className)
109 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
110 InvocationTargetException, ClassNotFoundException {
111 return defineClassFromJAR(peerClass, jarFile, className, null, null);
112 }
113
114 /**
115 * Define the class as stored in clsFile, in the same loader as peerClass.
116 *
117 * If a class exists both in the classpath, as well as in the list of URLs of a URLClassLoader,
118 * by default, the URLClassLoader will not define the class, and instead will delegate to the
119 * app loader. This method is an easy way to force the class to be defined by the URLClassLoader.
120 *
121 * Optionally, you can modify the contents of the classfile buffer. See comments in
122 * defineModifiedClass.
123 */
124 public static Class<?> defineClassFromJAR(Class<?> peerClass, File jarFile, String className,
125 String fromString, String toString)
126 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
127 InvocationTargetException, ClassNotFoundException
128 {
129 byte[] buff = getClassFileFromJar(jarFile, className);
130
131 if (fromString != null) {
132 replace(buff, fromString, toString);
133 }
134
135 //System.out.println("Loading from: " + ent + " (" + buff.length + " bytes)");
136
137 Lookup lookup = MethodHandles.privateLookupIn(peerClass, MethodHandles.lookup());
138 Class<?> cls = lookup.defineClass(buff);
139
140 //System.out.println("Loaded : " + cls);
141 return cls;
142 }
143
144 public static byte[] getClassFileFromJar(File jarFile, String className) throws FileNotFoundException, IOException {
145 JarFile jf = new JarFile(jarFile);
146 JarEntry ent = jf.getJarEntry(className.replace('.', '/') + ".class");
147
148 try (DataInputStream dis = new DataInputStream(jf.getInputStream(ent))) {
149 byte[] buff = new byte[(int)ent.getSize()];
150 dis.readFully(buff);
151 return buff;
152 }
153 }
154
155 }