1 <!doctype html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> 2 <html> 3 <head> 4 <meta http-equiv="content-type" content="text/html; charset=iso-8859-1"> 5 <meta http-equiv="content-style-type" content="text/css"> 6 <link rel="stylesheet" type="text/css" href="style.css"> 7 <title>ProGuard Introduction</title> 8 <script type="text/javascript" language="JavaScript"> 9 <!-- 10 if (window.self==window.top) 11 window.top.location.replace("../index.html#"+window.location.pathname+window.location.hash); 12 else { 13 var hash="#"+window.location.pathname.replace(window.top.location.pathname.replace("index.html", ""), ""); 14 if (window.top.location.hash!=hash) 15 window.top.location.hash=hash; 16 } 17 //--> 18 </script> 19 </head> 20 <body> 21 22 <h2>Introduction</h2> 23 24 <b>ProGuard</b> is a Java class file shrinker, optimizer, obfuscator, and 25 preverifier. The shrinking step detects and removes unused classes, fields, 26 methods, and attributes. The optimization step analyzes and optimizes the 27 bytecode of the methods. The obfuscation step renames the remaining classes, 28 fields, and methods using short meaningless names. These first steps make the 29 code base smaller, more efficient, and harder to reverse-engineer. The final 30 preverification step adds preverification information to the classes, which is 31 required for Java Micro Edition and for Java 6 and higher. 32 <p> 33 Each of these steps is optional. For instance, ProGuard can also be used to 34 just list dead code in an application, or to preverify class files for 35 efficient use in Java 6. 36 <p> 37 38 <table class="diagram" align="center"> 39 40 <tr> 41 <td rowspan="4" class="lightblock">Input jars</td> 42 <td colspan="8" class="transparentblock"></td> 43 </tr> 44 45 <tr> 46 <td rowspan="2" class="transparentblock"></td> 47 <td rowspan="3" class="lightblock">Shrunk code</td> 48 <td colspan="6" class="transparentblock"></td> 49 </tr> 50 51 <tr> 52 <td class="transparentblock"></td> 53 <td rowspan="2" class="lightblock">Optim. code</td> 54 <td colspan="3" class="transparentblock"></td> 55 <td rowspan="2" class="lightblock">Output jars</td> 56 </tr> 57 58 <tr> 59 <td class="transparentblock">- shrink →</td> 60 <td class="transparentblock">- optimize →</td> 61 <td class="transparentblock">- obfuscate →</td> 62 <td class="lightblock">Obfusc. code</td> 63 <td class="transparentblock">- preverify →</td> 64 </tr> 65 66 <tr> 67 <td class="darkblock">Library jars</td> 68 <td colspan="7" class="transparentblock">------------------------------- (unchanged) -------------------------------→</td> 69 <td class="darkblock">Library jars</td> 70 </tr> 71 72 </table> 73 <p> 74 75 ProGuard first reads the <b>input jars</b> (or wars, ears, zips, or 76 directories). It then subsequently shrinks, optimizes, obfuscates, and 77 preverifies them. You can optionally let ProGuard perform multiple 78 optimization passes. ProGuard writes the processed results to one or 79 more <b>output jars</b> (or wars, ears, zips, or directories). The input may 80 contain resource files, whose names and contents can optionally be updated to 81 reflect the obfuscated class names. 82 <p> 83 ProGuard requires the <b>library jars</b> (or wars, ears, zips, or 84 directories) of the input jars to be specified. These are essentially the 85 libraries that you would need for compiling the code. ProGuard uses them to 86 reconstruct the class dependencies that are necessary for proper processing. 87 The library jars themselves always remain unchanged. You should still put them 88 in the class path of your final application. 89 90 <h3>Entry points</h3> 91 92 In order to determine which code has to be preserved and which code can be 93 discarded or obfuscated, you have to specify one or more <i>entry points</i> to 94 your code. These entry points are typically classes with main methods, applets, 95 midlets, activities, etc. 96 <ul> 97 <li>In the <b>shrinking step</b>, ProGuard starts from these seeds and 98 recursively determines which classes and class members are used. All other 99 classes and class members are discarded.</li> 100 101 <li>In the <b>optimization step</b>, ProGuard further optimizes the code. 102 Among other optimizations, classes and methods that are not entry points 103 can be made private, static, or final, unused parameters can be removed, 104 and some methods may be inlined.</li> 105 106 <li>In the <b>obfuscation step</b>, ProGuard renames classes and class members 107 that are not entry points. In this entire process, keeping the entry 108 points ensures that they can still be accessed by their original names.</li> 109 110 <li>The <b>preverification step</b> is the only step that doesn't have to know 111 the entry points.</li> 112 </ul> 113 <p> 114 The <a href="usage.html">Usage section</a> of this manual describes the 115 necessary <a href="usage.html#keepoptions"><code>-keep</code> options</a> and 116 the <a href="examples.html">Examples section</a> provides plenty of examples. 117 118 <h3>Reflection</h3> 119 120 Reflection and introspection present particular problems for any automatic 121 processing of code. In ProGuard, classes or class members in your code that 122 are created or invoked dynamically (that is, by name) have to be specified as 123 entry points too. For example, <code>Class.forName()</code> constructs may 124 refer to any class at run-time. It is generally impossible to compute which 125 classes have to be preserved (with their original names), since the class 126 names might be read from a configuration file, for instance. You therefore 127 have to specify them in your ProGuard configuration, with the same 128 simple <code>-keep</code> options. 129 <p> 130 However, ProGuard will already detect and handle the following cases for you: 131 132 <ul> 133 <li><code>Class.forName("SomeClass")</code></li> 134 <li><code>SomeClass.class</code></li> 135 <li><code>SomeClass.class.getField("someField")</code></li> 136 <li><code>SomeClass.class.getDeclaredField("someField")</code></li> 137 <li><code>SomeClass.class.getMethod("someMethod", new Class[] {})</code></li> 138 <li><code>SomeClass.class.getMethod("someMethod", new Class[] { A.class })</code></li> 139 <li><code>SomeClass.class.getMethod("someMethod", new Class[] { A.class, B.class })</code></li> 140 <li><code>SomeClass.class.getDeclaredMethod("someMethod", new Class[] {})</code></li> 141 <li><code>SomeClass.class.getDeclaredMethod("someMethod", new Class[] { A.class })</code></li> 142 <li><code>SomeClass.class.getDeclaredMethod("someMethod", new Class[] { A.class, B.class })</code></li> 143 <li><code>AtomicIntegerFieldUpdater.newUpdater(SomeClass.class, "someField")</code></li> 144 <li><code>AtomicLongFieldUpdater.newUpdater(SomeClass.class, "someField")</code></li> 145 <li><code>AtomicReferenceFieldUpdater.newUpdater(SomeClass.class, SomeType.class, "someField")</code></li> 146 </ul> 147 148 The names of the classes and class members may of course be different, but the 149 constructs should be literally the same for ProGuard to recognize them. The 150 referenced classes and class members are preserved in the shrinking phase, and 151 the string arguments are properly updated in the obfuscation phase. 152 <p> 153 Furthermore, ProGuard will offer some suggestions if keeping some classes or 154 class members appears necessary. For example, ProGuard will note constructs 155 like "<code>(SomeClass)Class.forName(variable).newInstance()</code>". These 156 might be an indication that the class or interface <code>SomeClass</code> 157 and/or its implementations may need to be preserved. You can then adapt your 158 configuration accordingly. 159 <p> 160 For proper results, you should at least be somewhat familiar with the code 161 that you are processing. Obfuscating code that performs a lot of reflection 162 may require trial and error, especially without the necessary information 163 about the internals of the code. 164 165 <hr /> 166 <noscript><div><a target="_top" href="../index.html" class="button">Show menu</a></div></noscript> 167 <address> 168 Copyright © 2002-2013 169 <a target="other" href="http://www.lafortune.eu/">Eric Lafortune</a>. 170 </address> 171 </body> 172 </html> 173
