Java Instrument 示例
Agent项目
AtmTransformer.java
import java.io.IOException;
import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.security.ProtectionDomain;
import javassist.*;
public class AtmTransformer implements ClassFileTransformer {
private static final String WITHDRAW_MONEY_METHOD = "withdrawMoney";
/** The internal form class name of the class to transform */
private String targetClassName;
/** The class loader of the class we want to transform */
private ClassLoader targetClassLoader;
public AtmTransformer(String targetClassName, ClassLoader targetClassLoader) {
this.targetClassName = targetClassName;
this.targetClassLoader = targetClassLoader;
}
@Override
public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
ProtectionDomain protectionDomain, byte[] classfileBuffer) throws IllegalClassFormatException {
byte[] byteCode = classfileBuffer;
String finalTargetClassName = this.targetClassName.replaceAll("\\.", "/"); //replace . with /
if (!className.equals(finalTargetClassName)) {
return byteCode;
}
if (className.equals(finalTargetClassName) && loader.equals(targetClassLoader)) {
System.out.println("[Agent] Transforming class MyAtm");
try {
ClassPool cp = ClassPool.getDefault();
CtClass cc = cp.get(targetClassName);
CtMethod m = cc.getDeclaredMethod(WITHDRAW_MONEY_METHOD);
m.addLocalVariable("startTime", CtClass.longType);
m.insertBefore("startTime = System.currentTimeMillis();");
StringBuilder endBlock = new StringBuilder();
m.addLocalVariable("endTime", CtClass.longType);
m.addLocalVariable("opTime", CtClass.longType);
endBlock.append("endTime = System.currentTimeMillis();");
endBlock.append("opTime = (endTime-startTime)/1000;");
endBlock.append("System.out.println(\"[Application] Withdrawal operation completed in:\" + opTime + \" seconds!\");");
m.insertAfter(endBlock.toString());
byteCode = cc.toBytecode();
cc.detach();
} catch (NotFoundException | CannotCompileException | IOException e) {
e.printStackTrace();
}
}
return byteCode;
}
}
MyInstrumentationAgent.java
import java.lang.instrument.Instrumentation;
public class MyInstrumentationAgent {
public static void premain(String agentArgs, Instrumentation inst) {
System.out.println("[Agent] In premain method");
String className = "com.company.MyAtm";
transformClass(className,inst);
}
public static void agentmain(String agentArgs, Instrumentation inst) {
System.out.println("[Agent] In agentmain method");
String className = "com.company.MyAtm";
transformClass(className,inst);
}
private static void transformClass(String className, Instrumentation instrumentation) {
Class<?> targetCls = null;
ClassLoader targetClassLoader = null;
// see if we can get the class using forName
try {
targetCls = Class.forName(className);
targetClassLoader = targetCls.getClassLoader();
transform(targetCls, targetClassLoader, instrumentation);
return;
} catch (Exception ex) {
System.err.println("Class [" + className + "] not found with Class.forName");
}
// otherwise iterate all loaded classes and find what we want
for(Class<?> clazz: instrumentation.getAllLoadedClasses()) {
if(clazz.getName().equals(className)) {
targetCls = clazz;
targetClassLoader = targetCls.getClassLoader();
transform(targetCls, targetClassLoader, instrumentation);
return;
}
}
throw new RuntimeException("Failed to find class [" + className + "]");
}
private static void transform(Class<?> clazz, ClassLoader classLoader, Instrumentation instrumentation) {
AtmTransformer dt = new AtmTransformer(clazz.getName(), classLoader);
instrumentation.addTransformer(dt, true);
try {
instrumentation.retransformClasses(clazz);
} catch (Exception ex) {
throw new RuntimeException("Transform failed for class: [" + clazz.getName() + "]", ex);
}
}
}
MANIFEST.MF
Agent-Class: MyInstrumentationAgent
Can-Redefine-Classes: true
Can-Retransform-Classes: true
Premain-Class: MyInstrumentationAgent
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.example</groupId>
<artifactId>MyFirstAgent</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>org.javassist</groupId>
<artifactId>javassist</artifactId>
<version>3.27.0-GA</version>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
<!-- <plugin>-->
<!-- <groupId>org.apache.maven.plugins</groupId>-->
<!-- <artifactId>maven-jar-plugin</artifactId>-->
<!-- <configuration>-->
<!-- <archive>-->
<!-- <manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile>-->
<!-- </archive>-->
<!-- </configuration>-->
<!-- </plugin>-->
</plugins>
</build>
</project>
agent依赖打包后，就可以注入了
控制程序
AgentLoader.java
package com.company;
import com.sun.tools.attach.VirtualMachine;
import java.io.File;
import java.util.Optional;
public class AgentLoader {
public static void run(String[] args) {
String agentFilePath = "/Users/xxx/Desktop/MyFirstAgent/target/MyFirstAgent-1.0-SNAPSHOT-jar-with-dependencies.jar";
String applicationName = "MyAtmApplication";
//iterate all jvms and get the first one that matches our application name
Optional<String> jvmProcessOpt = Optional.ofNullable(VirtualMachine.list()
.stream()
.filter(jvm -> {
System.out.println("jvm:{}" + jvm.displayName());
return jvm.displayName().contains(applicationName);
})
.findFirst().get().id());
if(!jvmProcessOpt.isPresent()) {
System.err.println("Target Application not found");
return;
}
File agentFile = new File(agentFilePath);
try {
String jvmPid = jvmProcessOpt.get();
System.out.println("Attaching to target JVM with PID: " + jvmPid);
VirtualMachine jvm = VirtualMachine.attach(jvmPid);
jvm.loadAgent(agentFile.getAbsolutePath());
jvm.detach();
System.out.println("Attached to target JVM and loaded Java agent successfully");
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}
Launcher.java
package com.company;
public class Launcher {
public static void main(String[] args) throws Exception {
if(args[0].equals("StartMyAtmApplication")) {
new MyAtmApplication().run(args);
} else if(args[0].equals("LoadAgent")) {
new AgentLoader().run(args);
}
}
}
MyAtm.java
package com.company;
public class MyAtm {
private static final int account = 10;
public static void withdrawMoney(int amount) throws InterruptedException {
Thread.sleep(2000l); //processing going on here
System.out.println("[Application] Successful Withdrawal of [" + amount + "] units! ");
}
}
MyAtmApplication.java
package com.company;
public class MyAtmApplication {
public static void run(String[] args) throws Exception {
System.out.println("[Application] Starting ATM application");
MyAtm.withdrawMoney(Integer.parseInt(args[2]));
Thread.sleep(Long.valueOf(args[1]));
MyAtm.withdrawMoney(Integer.parseInt(args[3]));
}
}
pom.xml
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.company</groupId>
<artifactId>java-instrument-sample</artifactId>
<version>1.0-SNAPSHOT</version>
<properties>
<maven.compiler.source>8</maven.compiler.source>
<maven.compiler.target>8</maven.compiler.target>
</properties>
<dependencies>
<dependency>
<groupId>com.sun</groupId>
<artifactId>tools</artifactId>
<version>1.8</version>
<scope>system</scope>
<systemPath>/Library/Java/JavaVirtualMachines/jdk1.8.0_201.jdk/Contents/Home/lib/tools.jar</systemPath>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<artifactId>maven-assembly-plugin</artifactId>
<configuration>
<archive>
<manifest>
<mainClass>com.company.Launcher</mainClass>
</manifest>
</archive>
<descriptorRefs>
<descriptorRef>jar-with-dependencies</descriptorRef>
</descriptorRefs>
</configuration>
</plugin>
</plugins>
</build>
</project>
启动类在Lancher，注意穿进去的参数
