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arthas/_sources/jad.md.txt

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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
|参数名称|参数说明|
|---:|:---|
|*class-pattern*|类名表达式匹配|
|`[c:]`|类所属 ClassLoader 的 hashcode|
|[E]|开启正则表达式匹配,默认为通配符匹配|
### 使用参考
#### 编绎`java.lang.String`
```java
$ 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);
}
...
```
#### 反编绎指定的函数
```java
$ 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.
```
#### 反编绎时指定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;
```java
$ 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.
```