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songlonqi-javasonglonqi-java
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‎README.md‎

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# agent-attach-java
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# agent-attach-java
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## 原理
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Attach 根本原理是使用文件 Socket 通讯, 就是往一个文件中写入 `load instrument xxx.jar=params`, 再给 jvm 一个 SIGQUIT 信号, 之后 jvm 读取 socket 文件, 加载对应的 agent.
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## 如何在 jvm 运行时动态添加 agent
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1. 首先下载***指定***的 ddtrace , 并放到 /usr/local/ddtrace/
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```shell
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mkdir -p /usr/local/ddtrace
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cd /usr/local/ddtrace
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wget https://github.com/GuanceCloud/dd-trace-java/releases/download/v0.113.0-attach/dd-java-agent.jar
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```
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2. 启动 java 程序
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3. 启动 agent-attach-java.jar
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```shell
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# 命令的参数有三个 options download agent-jar 没有的话 都是默认值
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# options=""
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# download ="" 下个版本(指定版本下载)
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# agent-jar="/usr/local/ddtrace/dd-java-agent.jar"
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java -jar agent-attach-java.jar -options "dd.agent.port=9529"
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```

‎out/artifacts/agent_attach_java_jar/agent-attach-java.jar‎

5.4 MB
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‎pom.xml‎

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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
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<modelVersion>4.0.0</modelVersion>
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<groupId>javaagent-examples</groupId>
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<artifactId>javaagent-examples</artifactId>
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<name>javaagent-examples</name>
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<groupId>agent-attach-java</groupId>
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<artifactId>agent-attach-java</artifactId>
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<name>agent-attach-java</name>
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<version>1.0</version>
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<description>javaagent-examples</description>
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<description>agent-attach-java</description>
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<packaging>jar</packaging>
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<build>
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<finalName>javaagent-examples</finalName>
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<finalName>agent-attach-java</finalName>
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<plugins>
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<plugin>
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<groupId>org.apache.maven.plugins</groupId>
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<artifactId>maven-compiler-plugin</artifactId>
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<configuration>
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<source>1.6</source>
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<target>1.6</target>
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<source>1.8</source>
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<target>1.8</target>
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</configuration>
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</plugin>
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<plugin>
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<manifest>
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<mainClass>name.dhruba.javaagent.MyMainClass</mainClass>
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</manifest>
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<manifestEntries>
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<!-- <manifestEntries>
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<Premain-Class>name.dhruba.javaagent.MyJavaAgent</Premain-Class>
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<Agent-Class>name.dhruba.javaagent.MyJavaAgent</Agent-Class>
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<Can-Redefine-Classes>true</Can-Redefine-Classes>
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<Can-Retransform-Classes>true</Can-Retransform-Classes>
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</manifestEntries>
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</manifestEntries>-->
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</archive>
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</configuration>
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</execution>
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</dependency>
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<dependency>
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<groupId>com.sun</groupId>
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<artifactId>tools</artifactId>
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<version>1.6.0</version>
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<scope>system</scope>
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<systemPath>${java.home}/../lib/tools.jar</systemPath>
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<groupId>io.earcam.wrapped</groupId>
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<artifactId>com.sun.tools.attach</artifactId>
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<version>1.8.0_jdk8u131-b11</version>
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<scope>compile</scope>
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<type>jar</type>
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</dependency>
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<dependency>

‎src/main/java/META-INF/MANIFEST.MF‎

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Manifest-Version: 1.0
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Main-Class: name.dhruba.javaagent.MyMainClass
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src/main/java/name/dhruba/javaagent/MyClassFileTransformer.java renamed to src/main/java/name/dhruba/javaagent/ClassFileTransformer.java

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package name.dhruba.javaagent;
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import java.lang.instrument.ClassFileTransformer;
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import java.lang.instrument.IllegalClassFormatException;
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import java.security.ProtectionDomain;
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import org.objectweb.asm.ClassWriter;
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import org.objectweb.asm.Label;
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import org.objectweb.asm.MethodVisitor;
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import org.objectweb.asm.Opcodes;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class MyClassFileTransformer implements ClassFileTransformer, Opcodes {
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public class ClassFileTransformer implements java.lang.instrument.ClassFileTransformer, Opcodes {
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static final Logger logger = LoggerFactory.getLogger(MyClassFileTransformer.class);
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static final Logger logger = LoggerFactory.getLogger(ClassFileTransformer.class);
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@Override
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public byte[] transform(ClassLoader loader, String className, Class<?> classBeingRedefined,
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ProtectionDomain protectionDomain, byte[] classfileBuffer)
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throws IllegalClassFormatException {
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logger.info("class file transformer invoked for className: {}", className);
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/*
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if (className.equals("name/dhruba/user/MyUser")) {
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return cw.toByteArray();
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}
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*/
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return classfileBuffer;
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}

‎src/main/java/name/dhruba/javaagent/Config.java‎

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package name.dhruba.javaagent;
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public class Config {
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private String options;
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private String downloadAddress;
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private String agentJar;
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public String getOptions() {
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return options;
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}
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public String getDownloadAddress() {
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return downloadAddress;
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}
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public String getAgentJar() {
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return agentJar;
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}
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private Config(String options,String downloadAddress,String agentJar){
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this.options = options;
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this.downloadAddress = downloadAddress;
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this.agentJar = agentJar;
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}
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static Config parse(String... args){
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String option = "";
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String downloadAddr= "";
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String currentArg = "";
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String agentJar= "";
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for(String arg : args){
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if (arg.startsWith("-")){
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currentArg =arg;
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}else {
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switch (currentArg){
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case "options":
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option = arg;
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case "download":
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downloadAddr = arg;
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case "agent-jar":
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agentJar = arg;
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}
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}
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}
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return new Config(option,downloadAddr,agentJar);
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}
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}

‎src/main/java/name/dhruba/javaagent/JavaAgentLoader.java‎

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package name.dhruba.javaagent;
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import java.lang.management.ManagementFactory;
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import java.util.List;
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import java.util.Properties;
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import com.sun.tools.attach.VirtualMachineDescriptor;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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import com.sun.tools.attach.VirtualMachine;
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public class JavaAgentLoader {
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static final Logger logger = LoggerFactory.getLogger(JavaAgentLoader.class);
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private static final String jarFilePath = "/usr/local/ddtrace/dd-java-agent.jar";
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public static void loadAgent(String agentJar ,String options) {
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logger.info("dynamically loading javaagent");
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String nameOfRunningVM = ManagementFactory.getRuntimeMXBean().getName();
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int p = nameOfRunningVM.indexOf('@');
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String pid = nameOfRunningVM.substring(0, p);
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System.out.println("------------------into-------------");
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System.out.println("------------------p-------------"+p);
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System.out.println("------------------pid-------------"+pid);
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System.out.println("------------------args-------------"+options);
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try {
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List<VirtualMachineDescriptor> list = VirtualMachine.list();
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for (int i = 0; i < list.size(); i++) {
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VirtualMachineDescriptor virtualMachineDescriptor = list.get(i);
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String version = virtualMachineDescriptor.id();
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System.out.println(version);
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System.out.println(virtualMachineDescriptor.id());
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System.out.println(virtualMachineDescriptor.displayName());
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System.out.println(virtualMachineDescriptor.toString());
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VirtualMachine attach = VirtualMachine.attach(version);
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if (agentJar != null && !agentJar.equals("")){
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attach.loadAgent(jarFilePath, options);
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}else {
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attach.loadAgent(agentJar, options);
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}
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Properties properties = attach.getAgentProperties();
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Properties sysproperties = attach.getSystemProperties();
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System.out.println( properties.toString());
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System.out.println( sysproperties.toString());
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System.out.println("DdTrace attach agent to displayName is:"+virtualMachineDescriptor.displayName());
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attach.detach();
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}
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// -------------
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// VirtualMachine vm = VirtualMachine.attach(pid);
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// vm.loadAgent(jarFilePath, "Ddd.env:test,Ddd.service.name:demo001,Ddd.agent.port:9529");// 参数
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// vm.detach();
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} catch (Exception e) {
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throw new RuntimeException(e);
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}
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}
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}

‎src/main/java/name/dhruba/javaagent/MyJavaAgent.java‎

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* @param inst
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* @throws Exception
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*/
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public static void premain(String args, Instrumentation inst) throws Exception {
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logger.info("premain method invoked with args: {} and inst: {}", args, inst);
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instrumentation = inst;
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instrumentation.addTransformer(new MyClassFileTransformer());
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}
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// public static void premain(String args, Instrumentation inst) throws Exception {
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// logger.info("premain method invoked with args: {} and inst: {}", args, inst);
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// instrumentation = inst;
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// instrumentation.addTransformer(new MyClassFileTransformer());
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// }
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/**
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* JVM hook to dynamically load javaagent at runtime.
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* @param inst
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* @throws Exception
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*/
40-
public static void agentmain(String args, Instrumentation inst) throws Exception {
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logger.info("agentmain method invoked with args: {} and inst: {}", args, inst);
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instrumentation = inst;
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instrumentation.addTransformer(new MyClassFileTransformer());
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}
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// public static void agentmain(String args, Instrumentation inst) throws Exception {
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// logger.info("agentmain method invoked with args: {} and inst: {}", args, inst);
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// instrumentation = inst;
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// instrumentation.addTransformer(new MyClassFileTransformer());
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// }
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/**
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* Programmatic hook to dynamically load javaagent at runtime.
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*/
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public static void initialize() {
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if (instrumentation == null) {
51-
MyJavaAgentLoader.loadAgent();
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}
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}
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}

‎src/main/java/name/dhruba/javaagent/MyJavaAgentLoader.java‎

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This file was deleted.

‎src/main/java/name/dhruba/javaagent/MyMainClass.java‎

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import java.util.Arrays;
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import name.dhruba.user.MyUser;
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import org.slf4j.Logger;
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import org.slf4j.LoggerFactory;
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public class MyMainClass {
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static final Logger logger = LoggerFactory.getLogger(MyMainClass.class);
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static {
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MyJavaAgent.initialize();
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}
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/**
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* Main method.
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*
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*
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* @param args
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*/
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public static void main(String[] args) {
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Config config = Config.parse(args);
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// todo load agent ddtrace
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// MyJavaAgent.initialize(config.getAgentJar(),config.getOptions());
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JavaAgentLoader.loadAgent(config.getAgentJar(),config.getOptions());
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logger.info("main method invoked with args: {}", Arrays.asList(args));
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logger.info("userName: {}", new MyUser().getName());
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// logger.info("userName: {}", new MyUser().getName());
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}
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}

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