目录
一、Arthas学习
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>] |
java
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） |
java
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$0(Ljava/lang/String;Ljava/lang/String;)Ljava/lang/String;
Affect(row-cnt:167) cost in 24 ms.
java
[arthas@768]$ 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.
java
[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
java
$ 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<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);
}
...
java
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
java
[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。
java
[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
java
[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<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 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<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！