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157 lines
4.2 KiB
Markdown
157 lines
4.2 KiB
Markdown
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> Decompile the specified classes.
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`jad` helps to decompile the byte code running in JVM to the source code to assist you to understand the logic behind better.
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* The decompiled code is syntax highlighted for better readability in Arthas console.
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* It is possible that there's grammar error in the decompiled code, but it should not affect your interpretation.
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### Options
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|Name|Specification|
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|---:|:---|
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|*class-pattern*|pattern for the class name|
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|`[c:]`|hashcode of the class loader that loads the class|
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|`[classLoaderClass:]`| The class name of the ClassLoader that executes the expression. |
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|`[E]`|turn on regex match while the default is wildcard match|
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### Usage
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#### Decompile `java.lang.String`
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`jad java.lang.String`{{execute T2}}
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```java
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$ jad java.lang.String
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ClassLoader:
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Location:
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/*
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* Decompiled with CFR 0_132.
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*/
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package java.lang;
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import java.io.ObjectStreamField;
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...
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public final class String
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implements Serializable,
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Comparable<String>,
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CharSequence {
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private final char[] value;
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private int hash;
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private static final long serialVersionUID = -6849794470754667710L;
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private static final ObjectStreamField[] serialPersistentFields = new ObjectStreamField[0];
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public static final Comparator<String> CASE_INSENSITIVE_ORDER = new CaseInsensitiveComparator();
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public String(byte[] arrby, int n, int n2) {
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String.checkBounds(arrby, n, n2);
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this.value = StringCoding.decode(arrby, n, n2);
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}
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...
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```
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#### Print source only
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By default, the decompile result will have the `ClassLoader` information. With the `--source-only` option, you can print only the source code. Conveniently used with the [mc](mc.md)/[redefine](redefine.md) commands.
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`jad --source-only java.lang.String`{{execute T2}}
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```
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$ jad --source-only java.lang.String
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...
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@Override
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public int compare(String string, String string2) {
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int n = string.length();
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int n2 = string2.length();
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int n3 = Math.min(n, n2);
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for (int i = 0; i < n3; ++i) {
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char c;
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char c2 = string.charAt(i);
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if (c2 == (c = string2.charAt(i)) || (c2 = Character.toUpperCase(c2)) == (c = Character.toUpperCase(c)) || (c2 = Character.toLowerCase(c2)) == (c = Character.toLowerCase(c))) continue;
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return c2 - c;
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}
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return n - n2;
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}
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private Object readResolve() {
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return String.CASE_INSENSITIVE_ORDER;
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}
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}
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}
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```
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#### Decompile the specified method
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`jad java.lang.String toString`{{execute T2}}
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```java
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$ jad java.lang.String toString
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ClassLoader:
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Location:
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@Override
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public String toString() {
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return this;
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}
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Affect(row-cnt:2) cost in 407 ms.
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```
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#### Decompile with specified classLoader
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> If the target class is loaded by multiple classloaders, `jad` outputs the `hashcode` of the corresponding classloaders, then you can re-run `jad` and specify `-c <hashcode>` to decompile the target class from the specified classloader.
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Examples:
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```java
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$ jad org.apache.log4j.Logger
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Found more than one class for: org.apache.log4j.Logger, Please use jad -c hashcode org.apache.log4j.Logger
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HASHCODE CLASSLOADER
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69dcaba4 +-monitor's ModuleClassLoader
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6e51ad67 +-java.net.URLClassLoader@6e51ad67
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+-sun.misc.Launcher$AppClassLoader@6951a712
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+-sun.misc.Launcher$ExtClassLoader@6fafc4c2
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2bdd9114 +-pandora-qos-service's ModuleClassLoader
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4c0df5f8 +-pandora-framework's ModuleClassLoader
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Affect(row-cnt:0) cost in 38 ms.
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```
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```java
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$ jad org.apache.log4j.Logger -c 69dcaba4
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ClassLoader:
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+-monitor's ModuleClassLoader
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Location:
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/Users/admin/app/log4j-1.2.14.jar
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package org.apache.log4j;
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import org.apache.log4j.spi.*;
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public class Logger extends Category
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{
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private static final String FQCN;
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protected Logger(String name)
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{
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super(name);
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}
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...
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Affect(row-cnt:1) cost in 190 ms.
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```
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For classloader with only one instance, it can be specified by `--classLoaderClass` using class name, which is more convenient to use.
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The value of `--classloaderclass` is the class name of classloader. It can only work when it matches a unique classloader instance. The purpose is to facilitate the input of general commands. However, `-c <hashcode>` is dynamic.
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