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

---

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 ]	指定 class 的 ClassLoader#toString() 返回值。长格式[classLoaderStr ]

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.MathGame
 class-info        demo.MathGame
 code-source       /C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jar
 name              demo.MathGame
 isInterface       false
 isAnnotation      false
 isEnum            false
 isAnonymousClass  false
 isArray           false
 isLocalClass      false
 isMemberClass     false
 isPrimitive       false
 isSynthetic       false
 simple-name       MathGame
 modifier          public
 annotation
 interfaces
 super-class       +-java.lang.Object
 class-loader      +-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7
                     +-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989
 classLoaderHash   4aa298b7

Affect(row-cnt:1) cost in 14 ms.

打印出类的 Field 信息
[arthas@768]$ sc -d -f demo.MathGame
 class-info        demo.MathGame
 code-source       /C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jar
 name              demo.MathGame
 isInterface       false
 isAnnotation      false
 isEnum            false
 isAnonymousClass  false
 isArray           false
 isLocalClass      false
 isMemberClass     false
 isPrimitive       false
 isSynthetic       false
 simple-name       MathGame
 modifier          public
 annotation
 interfaces
 super-class       +-java.lang.Object
 class-loader      +-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7
                     +-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989
 classLoaderHash   4aa298b7
 fields            name     random
                   type     java.util.Random
                   modifier private,static
                   value    java.util.Random@127d1896

                   name     illegalArgumentCount
                   type     int
                   modifier private


Affect(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 (Ljava/lang/StringBuilder;)V
java.lang.String ([CIILjava/lang/Void;)V
java.lang.String (Ljava/lang/AbstractStringBuilder;Ljava/lang/Void;)V
java.lang.String (Ljava/nio/charset/Charset;[BII)V
java.lang.String ([BIILjava/nio/charset/Charset;)V
java.lang.String ([BLjava/lang/String;)V
java.lang.String ([BLjava/nio/charset/Charset;)V
java.lang.String ([BII)V
java.lang.String ([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 toString
 declaring-class  java.lang.String
 method-name      toString
 modifier         public
 annotation
 parameters
 return           java.lang.String
 exceptions
 classLoaderHash  null

Affect(row-cnt:1) cost in 7 ms.

[arthas@768]$ sm demo.MathGame
demo.MathGame ()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.String

ClassLoader:

Location:

        /*
         * Decompiled with CFR.
         */
        package java.lang;

        import java.io.ObjectStreamField;
        import java.io.Serializable;
...
        public final class String
        implements Serializable,
        Comparable,
        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 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 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 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 primeFactors(int number) {
/*44*/         if (number < 2) {
/*45*/             ++this.illegalArgumentCount;
                   throw new IllegalArgumentException("number is: " + number + ", need >= 2");
               }
               ArrayList result = new ArrayList();
/*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 main

ClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7
  +-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989

Location:
/C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jar

       public 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 false

ClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7
  +-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989

Location:
/C:/Users/Administrator/.arthas/lib/3.7.1/arthas/math-game.jar

public 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.MathGame

ClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7
  +-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989

Location:
/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 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 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 primeFactors(int number) {
/*44*/         if (number < 2) {
/*45*/             ++this.illegalArgumentCount;
                   throw new IllegalArgumentException("number is: " + number + ", need >= 2");
               }
               ArrayList result = new ArrayList();
/*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 4aa298b7

ClassLoader:
+-jdk.internal.loader.ClassLoaders$AppClassLoader@4aa298b7
  +-jdk.internal.loader.ClassLoaders$PlatformClassLoader@364f989

Location:
/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 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 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 primeFactors(int number) {
/*44*/         if (number < 2) {
/*45*/             ++this.illegalArgumentCount;
                   throw new IllegalArgumentException("number is: " + number + ", need >= 2");
               }
               ArrayList result = new ArrayList();
/*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！