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< a href = "https://github.com/alibaba/arthas/blob/master/site/src/site/sphinx/en/redefine.md" class = "fa fa-github" > Edit on GitHub< / a >
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< div class = "section" id = "redefine" >
< h1 > redefine< a class = "headerlink" href = "#redefine" title = "Permalink to this headline" > ¶< / a > < / h1 >
< blockquote >
< div > < p > Load the external < code class = "docutils literal notranslate" > < span class = "pre" > *.class< / span > < / code > files to re-define the loaded classes in JVM.< / p >
< / div > < / blockquote >
< p > Reference: < a class = "reference external" href = "https://docs.oracle.com/javase/8/docs/api/java/lang/instrument/Instrumentation.html#redefineClasses-java.lang.instrument.ClassDefinition...-" > Instrumentation#redefineClasses< / a > < / p >
< blockquote >
< div > < p > Notes: Re-defined classes cannot be restored. There are chances that redefining may fail due to some reasons, for example: there’ ’ < / p >
< / div > < / blockquote >
< blockquote >
< div > < p > The < code class = "docutils literal notranslate" > < span class = "pre" > reset< / span > < / code > command is not valid for classes that have been processed by < code class = "docutils literal notranslate" > < span class = "pre" > redefine< / span > < / code > . If you want to reset, you need < code class = "docutils literal notranslate" > < span class = "pre" > redefine< / span > < / code > the original bytecode.< / p >
< / div > < / blockquote >
< div class = "section" id = "options" >
< h2 > Options< a class = "headerlink" href = "#options" title = "Permalink to this headline" > ¶< / a > < / h2 >
< table border = "1" class = "docutils" >
< thead >
< tr >
< th align = "right" > Name< / th >
< th align = "left" > Specification< / th >
< / tr >
< / thead >
< tbody >
< tr >
< td align = "right" > < code > [c:]< / code > < / td >
< td align = "left" > hashcode of the class loader< / td >
< / tr >
< tr >
< td align = "right" > < code > [p:]< / code > < / td >
< td align = "left" > absolute path of the external < code > *.class< / code > , multiple paths are separated with 'space'< / td >
< / tr >
< / tbody >
< / table > < / div >
< div class = "section" id = "usage" >
< h2 > Usage< a class = "headerlink" href = "#usage" title = "Permalink to this headline" > ¶< / a > < / h2 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > redefine /tmp/Test.class
redefine -c 327a647b /tmp/Test.class /tmp/Test$Inner.class< / pre > < / div >
< / div >
< / div >
< div class = "section" id = "use-with-the-jad-mc-command" >
< h2 > Use with the jad/mc command< a class = "headerlink" href = "#use-with-the-jad-mc-command" title = "Permalink to this headline" > ¶< / a > < / h2 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > jad --source-only com.example.demo.arthas.user.UserController > /tmp/UserController.java
mc /tmp/UserController.java -d /tmp
redefine /tmp/com/example/demo/arthas/user/UserController.class< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > Use < code class = "docutils literal notranslate" > < span class = "pre" > jad< / span > < / code > command to decompile bytecode, and then you can use other editors, such as vim to modify the source code.< / p > < / li >
< li > < p > < code class = "docutils literal notranslate" > < span class = "pre" > mc< / span > < / code > command to compile the modified code< / p > < / li >
< li > < p > Load new bytecode with < code class = "docutils literal notranslate" > < span class = "pre" > redefine< / span > < / code > command< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "tips-for-uploading-class-files-to-the-server" >
< h2 > Tips for uploading .class files to the server< a class = "headerlink" href = "#tips-for-uploading-class-files-to-the-server" title = "Permalink to this headline" > ¶< / a > < / h2 >
< p > The < code class = "docutils literal notranslate" > < span class = "pre" > mc< / span > < / code > command may fail. You can modify the code locally, compile it, and upload it to the server. Some servers do not allow direct uploading files, you can use the < code class = "docutils literal notranslate" > < span class = "pre" > base64< / span > < / code > command to bypass.< / p >
< ol >
< li > < p > Convert the < code class = "docutils literal notranslate" > < span class = "pre" > .class< / span > < / code > file to base64 first, then save it as result.txt< / p >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > Base64 < Test.class > result.txt< / pre > < / div >
< / div >
< / li >
< li > < p > Login the server, create and edit < code class = "docutils literal notranslate" > < span class = "pre" > result.txt< / span > < / code > , copy the local content, paste and save< / p > < / li >
< li > < p > Restore < code class = "docutils literal notranslate" > < span class = "pre" > result.txt< / span > < / code > on the server to < code class = "docutils literal notranslate" > < span class = "pre" > .class< / span > < / code > < / p >
< div class = "highlight-default notranslate" > < pre class = "literal-block" > Base64 -d < result.txt > Test.class< / pre >
< / div >
< / li >
< li > < p > Use the md5 command to verify that the < code class = "docutils literal notranslate" > < span class = "pre" > .class< / span > < / code > files are consistent.< / p > < / li >
< / ol >
< / div >
< div class = "section" id = "restrictions-of-the-redefine-command" >
< h2 > Restrictions of the redefine command< a class = "headerlink" href = "#restrictions-of-the-redefine-command" title = "Permalink to this headline" > ¶< / a > < / h2 >
< ul >
< li > < p > New field/method is not allowed< / p > < / li >
< li > < p > The function that is running, no exit can not take effect, such as the new < code class = "docutils literal notranslate" > < span class = "pre" > System.out.println< / span > < / code > added below, only the < code class = "docutils literal notranslate" > < span class = "pre" > run()< / span > < / code > function will take effect.< / p >
< div class = "highlight-java notranslate" > < div class = "highlight hljs" > < pre class = "java" > public class MathGame {
public static void main(String[] args) throws InterruptedException {
MathGame game = new MathGame();
while (true) {
game.run();
TimeUnit.SECONDS.sleep(1);
// This doesn' t work because the code keeps running in while
System.out.println(" in loop" );
}
}
public void run() throws InterruptedException {
// This works because the run() function ends completely every time
System.out.println(" call run()" );
try {
int number = random.nextInt();
List< Integer> primeFactors = primeFactors(number);
print(number, primeFactors);
} catch (Exception e) {
System.out.println(String.format(" illegalArgumentCount:%3d, " , illegalArgumentCount) + e.getMessage());
}
}< / pre > < / div >
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