Arthas(阿尔萨斯)--(三)

目录

一、Arthas学习

1、class/classloader相关命令一

1、sc

2、sm

2、class/classloader相关命令二

1、jad

2、mc

3、redefine

三、class/classloader相关命令三

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一、Arthas学习

Arthas(阿尔萨斯)--(一)

Arthas(阿尔萨斯)--(二)

1、class/classloader相关命令一

1、sc

sc：Search Class：查看JVM已加载的类信息，“Search-Class” 的简写，这个命令能搜索出所有已经加载到 JVM 中的 Class 信息，这个命令支持的参数有 [d]、[E]、[f] 和 [x:]

sc 默认开启了子类匹配功能，也就是说所有当前类的子类也会被搜索出来，想要精确的匹配，请打开options disable-sub-class true开关

参数名称	参数说明
class-pattern	类名表达式匹配
method-pattern	方法名表达式匹配
[d]	输出当前类的详细信息，包括这个类所加载的原始文件来源、类的声明、加载的 ClassLoader 等详细信息。 如果一个类被多个 ClassLoader 所加载，则会出现多次
[E]	开启正则表达式匹配，默认为通配符匹配
[f]	输出当前类的成员变量信息（需要配合参数-d 一起使用）
[x:]	指定输出静态变量时属性的遍历深度，默认为 0，即直接使用 toString 输出
[c:]	指定 class 的 ClassLoader 的 hashcode
[classLoaderClass:]	指定执行表达式的 ClassLoader 的 class name
[n:]	具有详细信息的匹配类的最大数量（默认为 100）
[cs <arg>]	指定 class 的 ClassLoader#toString() 返回值。长格式[classLoaderStr <arg>]

模糊搜索
[arthas@768]$ sc demo.*
demo.MathGame
Affect(row-cnt:1) cost in 13 ms.打印类的详细信息
[arthas@768]$ sc -d demo.MathGameclass-info        demo.MathGamecode-source       /C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jarname              demo.MathGameisInterface       falseisAnnotation      falseisEnum            falseisAnonymousClass  falseisArray           falseisLocalClass      falseisMemberClass     falseisPrimitive       falseisSynthetic       falsesimple-name       MathGamemodifier          publicannotationinterfacessuper-class       +-java.lang.Objectclass-loader      +-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989classLoaderHash   4aa298b7Affect(row-cnt:1) cost in 14 ms.打印出类的 Field 信息
[arthas@768]$ sc -d -f demo.MathGameclass-info        demo.MathGamecode-source       /C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jarname              demo.MathGameisInterface       falseisAnnotation      falseisEnum            falseisAnonymousClass  falseisArray           falseisLocalClass      falseisMemberClass     falseisPrimitive       falseisSynthetic       falsesimple-name       MathGamemodifier          publicannotationinterfacessuper-class       +-java.lang.Objectclass-loader      +-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989classLoaderHash   4aa298b7fields            name     randomtype     java.util.Randommodifier private,staticvalue    java.util.Random@127d1896name     illegalArgumentCounttype     intmodifier privateAffect(row-cnt:1) cost in 12 ms.

2、sm

sm：查看已加载类的方法信息

“Search-Method” 的简写，这个命令能搜索出所有已经加载了 Class 信息的方法信息。

sm 命令只能看到由当前类所声明 (declaring) 的方法，父类则无法看到。

参数名称	参数说明
class-pattern	类名表达式匹配
method-pattern	方法名表达式匹配
[d]	展示每个方法的详细信息
[E]	开启正则表达式匹配，默认为通配符匹配
[c:]	指定 class 的 ClassLoader 的 hashcode
[classLoaderClass:]	指定执行表达式的 ClassLoader 的 class name
[n:]	具有详细信息的匹配类的最大数量（默认为 100）

显示String类加载的方法
[arthas@768]$ sm java.lang.String
java.lang.String <init>(Ljava/lang/StringBuilder;)V
java.lang.String <init>([CIILjava/lang/Void;)V
java.lang.String <init>(Ljava/lang/AbstractStringBuilder;Ljava/lang/Void;)V
java.lang.String <init>(Ljava/nio/charset/Charset;[BII)V
java.lang.String <init>([BIILjava/nio/charset/Charset;)V
java.lang.String <init>([BLjava/lang/String;)V
java.lang.String <init>([BLjava/nio/charset/Charset;)V
java.lang.String <init>([BII)V
java.lang.String <init>([B)V
....
java.lang.String valueOfCodePoint(I)Ljava/lang/String;
java.lang.String describeConstable()Ljava/util/Optional;
java.lang.String lambda$stripIndent$3(ILjava/lang/String;)Ljava/lang/String;
java.lang.String lambda$indent$2(ILjava/lang/String;)Ljava/lang/String;
java.lang.String lambda$indent$1(Ljava/lang/String;)Ljava/lang/String;
java.lang.String lambda$indent$0(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
Affect(row-cnt:167) cost in 24 ms.

[arthas@768]$ sm -d java.lang.String toStringdeclaring-class  java.lang.Stringmethod-name      toStringmodifier         publicannotationparametersreturn           java.lang.StringexceptionsclassLoaderHash  nullAffect(row-cnt:1) cost in 7 ms.

[arthas@768]$ sm demo.MathGame
demo.MathGame <init>()V
demo.MathGame main([Ljava/lang/String;)V
demo.MathGame run()V
demo.MathGame print(ILjava/util/List;)V
demo.MathGame primeFactors(I)Ljava/util/List;
Affect(row-cnt:5) cost in 5 ms.

2、class/classloader相关命令二

1、jad

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；如需批量下载指定包的目录的 class 字节码

$ jad java.lang.StringClassLoader:Location:/** Decompiled with CFR.*/package java.lang;import java.io.ObjectStreamField;import java.io.Serializable;
...public final class Stringimplements 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[] byArray, int n, int n2, Charset charset) {
/*460*/         if (charset == null) {throw new NullPointerException("charset");}
/*462*/         String.checkBounds(byArray, n, n2);
/*463*/         this.value = StringCoding.decode(charset, byArray, n, n2);}
...

反编译只显示源码
[arthas@768]$ jad --source-only demo.MathGame/** Decompiled with CFR.*/package demo;import java.util.ArrayList;import java.util.List;import java.util.Random;import java.util.concurrent.TimeUnit;public class MathGame {private static Random random = new Random();private int illegalArgumentCount = 0;public static void main(String[] args) throws InterruptedException {MathGame game = new MathGame();while (true) {
/*16*/             game.run();
/*17*/             TimeUnit.SECONDS.sleep(1L);}}public void run() throws InterruptedException {try {
/*23*/             int number = random.nextInt() / 10000;
/*24*/             List<Integer> primeFactors = this.primeFactors(number);
/*25*/             MathGame.print(number, primeFactors);}catch (Exception e) {
/*28*/             System.out.println(String.format("illegalArgumentCount:%3d, ", this.illegalArgumentCount) + e.getMessage());}}public static void print(int number, List<Integer> primeFactors) {StringBuffer sb = new StringBuffer(number + "=");
/*34*/         for (int factor : primeFactors) {
/*35*/             sb.append(factor).append('*');}
/*37*/         if (sb.charAt(sb.length() - 1) == '*') {
/*38*/             sb.deleteCharAt(sb.length() - 1);}
/*40*/         System.out.println(sb);}public List<Integer> primeFactors(int number) {
/*44*/         if (number < 2) {
/*45*/             ++this.illegalArgumentCount;throw new IllegalArgumentException("number is: " + number + ", need >= 2");}ArrayList<Integer> result = new ArrayList<Integer>();
/*50*/         int i = 2;
/*51*/         while (i <= number) {
/*52*/             if (number % i == 0) {
/*53*/                 result.add(i);
/*54*/                 number /= i;
/*55*/                 i = 2;continue;}
/*57*/             ++i;}
/*61*/         return result;}}

反编译指定函数

[arthas@768]$ jad demo.MathGame mainClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989Location:
/C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jarpublic static void main(String[] args) throws InterruptedException {MathGame game = new MathGame();while (true) {
/*16*/         game.run();
/*17*/         TimeUnit.SECONDS.sleep(1L);}}Affect(row-cnt:1) cost in 117 ms.

反编译时不显示行号

--lineNumber 参数默认值为 true，显示指定为 false 则不打印行号。

[arthas@768]$ jad demo.MathGame main --lineNumber falseClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989Location:
/C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jarpublic static void main(String[] args) throws InterruptedException {MathGame game = new MathGame();while (true) {game.run();TimeUnit.SECONDS.sleep(1L);}
}Affect(row-cnt:1) cost in 101 ms.

反编译时指定 ClassLoader

[arthas@768]$ jad demo.MathGameClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989Location:
/C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jar/** Decompiled with CFR.*/package demo;import java.util.ArrayList;import java.util.List;import java.util.Random;import java.util.concurrent.TimeUnit;public class MathGame {private static Random random = new Random();private int illegalArgumentCount = 0;public static void main(String[] args) throws InterruptedException {MathGame game = new MathGame();while (true) {
/*16*/             game.run();
/*17*/             TimeUnit.SECONDS.sleep(1L);}}public void run() throws InterruptedException {try {
/*23*/             int number = random.nextInt() / 10000;
/*24*/             List<Integer> primeFactors = this.primeFactors(number);
/*25*/             MathGame.print(number, primeFactors);}catch (Exception e) {
/*28*/             System.out.println(String.format("illegalArgumentCount:%3d, ", this.illegalArgumentCount) + e.getMessage());}}public static void print(int number, List<Integer> primeFactors) {StringBuffer sb = new StringBuffer(number + "=");
/*34*/         for (int factor : primeFactors) {
/*35*/             sb.append(factor).append('*');}
/*37*/         if (sb.charAt(sb.length() - 1) == '*') {
/*38*/             sb.deleteCharAt(sb.length() - 1);}
/*40*/         System.out.println(sb);}public List<Integer> primeFactors(int number) {
/*44*/         if (number < 2) {
/*45*/             ++this.illegalArgumentCount;throw new IllegalArgumentException("number is: " + number + ", need >= 2");}ArrayList<Integer> result = new ArrayList<Integer>();
/*50*/         int i = 2;
/*51*/         while (i <= number) {
/*52*/             if (number % i == 0) {
/*53*/                 result.add(i);
/*54*/                 number /= i;
/*55*/                 i = 2;continue;}
/*57*/             ++i;}
/*61*/         return result;}}Affect(row-cnt:1) cost in 98 ms.
[arthas@768]$ jad demo.MathGame -c 4aa298b7ClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7+-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989Location:
/C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jar/** Decompiled with CFR.*/package demo;import java.util.ArrayList;import java.util.List;import java.util.Random;import java.util.concurrent.TimeUnit;public class MathGame {private static Random random = new Random();private int illegalArgumentCount = 0;public static void main(String[] args) throws InterruptedException {MathGame game = new MathGame();while (true) {
/*16*/             game.run();
/*17*/             TimeUnit.SECONDS.sleep(1L);}}public void run() throws InterruptedException {try {
/*23*/             int number = random.nextInt() / 10000;
/*24*/             List<Integer> primeFactors = this.primeFactors(number);
/*25*/             MathGame.print(number, primeFactors);}catch (Exception e) {
/*28*/             System.out.println(String.format("illegalArgumentCount:%3d, ", this.illegalArgumentCount) + e.getMessage());}}public static void print(int number, List<Integer> primeFactors) {StringBuffer sb = new StringBuffer(number + "=");
/*34*/         for (int factor : primeFactors) {
/*35*/             sb.append(factor).append('*');}
/*37*/         if (sb.charAt(sb.length() - 1) == '*') {
/*38*/             sb.deleteCharAt(sb.length() - 1);}
/*40*/         System.out.println(sb);}public List<Integer> primeFactors(int number) {
/*44*/         if (number < 2) {
/*45*/             ++this.illegalArgumentCount;throw new IllegalArgumentException("number is: " + number + ", need >= 2");}ArrayList<Integer> result = new ArrayList<Integer>();
/*50*/         int i = 2;
/*51*/         while (i <= number) {
/*52*/             if (number % i == 0) {
/*53*/                 result.add(i);
/*54*/                 number /= i;
/*55*/                 i = 2;continue;}
/*57*/             ++i;}
/*61*/         return result;}}Affect(row-cnt:1) cost in 81 ms.

2、mc

mc：Memory Compiler/内存编译器，编译.java文件生成.class。

3、redefine

三、class/classloader相关命令三

一个程序员最重要的能力是：写出高质量的代码！！
有道无术，术尚可求也，有术无道，止于术。
无论你是年轻还是年长，所有程序员都需要记住：时刻努力学习新技术，否则就会被时代抛弃！