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 static java.lang.invoke.MethodHandles.*;
29 import java.lang.reflect.*;
30 import java.util.jar.*;
31
32 public class Util {
33 /**
34 * Invoke the lookup.defineClass() class method to define the class stored in clsFile,
35 * with the following modification:
36 * <ul>
37 * <li> All ASCII strings in the class file bytes that matches fromString will be replaced with toString.
38 * NOTE: the two strings must be the exact same length.
39 * </ul>
40 */
41 public static Class<?> defineModifiedClass(ClassLoader loader, File clsFile, String fromString, String toString)
42 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
43 InvocationTargetException, ClassNotFoundException
44 {
45 try (DataInputStream dis = new DataInputStream(new FileInputStream(clsFile))) {
46 byte[] buff = new byte[(int)clsFile.length()];
47 dis.readFully(buff);
48 replace(buff, fromString, toString);
49
50 System.out.println("Loading from: " + clsFile + " (" + buff.length + " bytes)");
51
52
53 // We directly call into Lookup.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<?> target = Class.forName("Hello", false, loader);
57 Lookup lookup = privateLookupIn(target, lookup());
58 Class<?> cls = lookup.defineClass(buff);
59 System.out.println("Loaded : " + cls);
60
61 return cls;
62 }
63 }
64
65 /**
66 * @return the number of occurrences of the <code>from</code> string that
67 * have been replaced.
68 */
69 public static int replace(byte buff[], String from, String to) {
70 if (to.length() != from.length()) {
71 throw new RuntimeException("bad strings");
72 }
73 byte f[] = asciibytes(from);
74 byte t[] = asciibytes(to);
75 byte f0 = f[0];
76
77 int numReplaced = 0;
78 int max = buff.length - f.length;
79 for (int i=0; i<max; ) {
80 if (buff[i] == f0 && replace(buff, f, t, i)) {
81 i += f.length;
82 numReplaced ++;
83 } else {
84 i++;
85 }
86 }
87 return numReplaced;
88 }
89
90 public static boolean replace(byte buff[], byte f[], byte t[], int i) {
91 for (int x=0; x<f.length; x++) {
92 if (buff[x+i] != f[x]) {
93 return false;
94 }
95 }
96 for (int x=0; x<f.length; x++) {
97 buff[x+i] = t[x];
98 }
99 return true;
100 }
101
102 static byte[] asciibytes(String s) {
103 byte b[] = new byte[s.length()];
104 for (int i=0; i<b.length; i++) {
105 b[i] = (byte)s.charAt(i);
106 }
107 return b;
108 }
109
110 public static Class defineClassFromJAR(ClassLoader loader, File jarFile, String className)
111 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
112 InvocationTargetException, ClassNotFoundException {
113 return defineClassFromJAR(loader, jarFile, className, null, null);
114 }
115
116 /**
117 * Invoke the lookup.defineClass() class method to define the named class stored in a JAR file.
118 *
119 * If a class exists both in the classpath, as well as in the list of URLs of a URLClassLoader,
120 * by default, the URLClassLoader will not define the class, and instead will delegate to the
121 * app loader. This method is an easy way to force the class to be defined by the URLClassLoader.
122 *
123 * Optionally, you can modify the contents of the classfile buffer. See comments in
124 * defineModifiedClass.
125 */
126 public static Class<?> defineClassFromJAR(ClassLoader loader, File jarFile, String className,
127 String fromString, String toString)
128 throws FileNotFoundException, IOException, NoSuchMethodException, IllegalAccessException,
129 InvocationTargetException, ClassNotFoundException
130 {
131 byte[] buff = getClassFileFromJar(jarFile, className);
132
133 if (fromString != null) {
134 replace(buff, fromString, toString);
135 }
136
137 //System.out.println("Loading from: " + ent + " (" + buff.length + " bytes)");
138
139 Class<?> target = Class.forName("Hello", false, loader);
140 Lookup lookup = privateLookupIn(target, lookup());
141 Class<?> cls = lookup.defineClass(buff);
142
143 //System.out.println("Loaded : " + cls);
144 return cls;
145 }
146
147 public static byte[] getClassFileFromJar(File jarFile, String className) throws FileNotFoundException, IOException {
148 JarFile jf = new JarFile(jarFile);
149 JarEntry ent = jf.getJarEntry(className.replace('.', '/') + ".class");
150
151 try (DataInputStream dis = new DataInputStream(jf.getInputStream(ent))) {
152 byte[] buff = new byte[(int)ent.getSize()];
153 dis.readFully(buff);
154 return buff;
155 }
156 }
157
158 }