jad

反编译指定已加载类的源码

jad 命令将 JVM 中实际运行的 class 的 byte code 反编译成 java 代码，便于你理解业务逻辑；

• 在 Arthas Console 上，反编译出来的源码是带语法高亮的，阅读更方便
• 当然，反编译出来的 java 代码可能会存在语法错误，但不影响你进行阅读理解

参数说明

使用参考

编译java.lang.String

$ jad java.lang.String
ClassLoader:
Location:
/*
* Decompiled with CFR 0_132.
*/
package java.lang;
import java.io.ObjectStreamField;
...
public final class String
implements Serializable,
Comparable<String>,
CharSequence {
    private final char[] value;
    private int hash;
    private static final long serialVersionUID = -6849794470754667710L;
    private static final ObjectStreamField[] serialPersistentFields = new ObjectStreamField[0];
    public static final Comparator<String> CASE_INSENSITIVE_ORDER = new CaseInsensitiveComparator();
    public String(byte[] arrby, int n, int n2) {
        String.checkBounds(arrby, n, n2);
        this.value = StringCoding.decode(arrby, n, n2);
    }
...

反编绎时只显示源代码

默认情况下，反编译结果里会带有ClassLoader信息，通过--source-only选项，可以只打印源代码。方便和mc/redefine命令结合使用。

$ jad --source-only demo.MathGame
/*
 * Decompiled with CFR 0_132.
 */
package demo;
import java.io.PrintStream;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
import java.util.concurrent.TimeUnit;
public class MathGame {
    private static Random random = new Random();
    public int illegalArgumentCount = 0;
...

反编译指定的函数

$ jad demo.MathGame main
ClassLoader:
+-sun.misc.Launcher$AppClassLoader@3d4eac69
+-sun.misc.Launcher$ExtClassLoader@66350f69
Location:
/private/tmp/arthas-demo.jar
public static void main(String[] args) throws InterruptedException {
    MathGame game = new MathGame();
    do {
        game.run();
        TimeUnit.SECONDS.sleep(1L);
    } while (true);
}
Affect(row-cnt:1) cost in 228 ms.

反编译时指定ClassLoader

当有多个 ClassLoader 都加载了这个类时，jad 命令会输出对应 ClassLoader 实例的 hashcode，然后你只需要重新执行 jad 命令，并使用参数 -c <hashcode> 就可以反编译指定 ClassLoader 加载的那个类了；

$ jad org.apache.log4j.Logger
Found more than one class for: org.apache.log4j.Logger, Please use jad -c hashcode org.apache.log4j.Logger
HASHCODE  CLASSLOADER
69dcaba4  +-monitor's ModuleClassLoader
6e51ad67  +-java.net.URLClassLoader@6e51ad67
            +-sun.misc.Launcher$AppClassLoader@6951a712
            +-sun.misc.Launcher$ExtClassLoader@6fafc4c2
2bdd9114  +-pandora-qos-service's ModuleClassLoader
4c0df5f8  +-pandora-framework's ModuleClassLoader
Affect(row-cnt:0) cost in 38 ms.
$ jad org.apache.log4j.Logger -c 69dcaba4
ClassLoader:
+-monitor's ModuleClassLoader
Location:
/Users/admin/app/log4j-1.2.14.jar
package org.apache.log4j;
import org.apache.log4j.spi.*;
public class Logger extends Category
{
    private static final String FQCN;
    protected Logger(String name)
    {
        super(name);
    }
...
Affect(row-cnt:1) cost in 190 ms.