新建MyAgent項目

pom文件

<?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.book.MyAgent</groupId><artifactId>MyAgent</artifactId><version>1.0</version><dependencies><dependency><groupId>javassist</groupId><artifactId>javassist</artifactId><version>3.12.1.GA</version></dependency><dependency><groupId>org.ow2.asm</groupId><artifactId>asm-all</artifactId><version>5.1</version></dependency></dependencies><build><plugins><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-compiler-plugin</artifactId><configuration><source>1.8</source><target>1.8</target></configuration></plugin><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-source-plugin</artifactId><version>3.0.1</version><executions><execution><id>attach-sources</id><phase>verify</phase><goals><goal>jar-no-fork</goal></goals></execution></executions></plugin><plugin><groupId>org.apache.maven.plugins</groupId><artifactId>maven-assembly-plugin</artifactId><version>2.6</version><configuration><descriptorRefs><descriptorRef>jar-with-dependencies</descriptorRef></descriptorRefs><archive><manifestFile>src/main/resources/META-INF/MANIFEST.MF</manifestFile></archive></configuration><executions><execution><id>assemble-all</id><phase>package</phase><goals><goal>single</goal></goals></execution></executions></plugin></plugins><resources><resource><directory>${basedir}/src/main/resources</directory></resource><resource><directory>${basedir}/src/main/java</directory></resource></resources></build>
</project>

AgentMain.java

import org.objectweb.asm.ClassReader;
import org.objectweb.asm.ClassVisitor;
import org.objectweb.asm.ClassWriter;
import org.objectweb.asm.MethodVisitor;
import org.objectweb.asm.Opcodes;import java.lang.instrument.ClassFileTransformer;
import java.lang.instrument.IllegalClassFormatException;
import java.lang.instrument.Instrumentation;
import java.security.ProtectionDomain;public class AgentMain {public static void premain(String agentOps, Instrumentation inst) {System.out.println("=========premain方法執行========");System.out.println(agentOps);//instrument(agentOps, inst);}public static void agentmain(String agentOps, Instrumentation inst) {instrument(agentOps, inst);}

?src\main\resources\META-INF下新建MANIFEST.MF

Manifest-Version: 1.0
Premain-Class: com.book.myagent.AgentMain
Agent-Class: com.book.myagent.AgentMain
Can-Redefine-Classes: true

注意會生成3個jar

新建第二個項目Test：

?

package com.book.test;public class HelloWorld {public static void main(String[] arg) {System.out.println("輸出>>>HelloWorld");}
}

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.book</groupId><artifactId>Test</artifactId><version>1.0-SNAPSHOT</version><packaging>jar</packaging><properties><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target></properties><build><plugins><plugin>    <artifactId>maven-assembly-plugin</artifactId>    <configuration>    <appendAssemblyId>false</appendAssemblyId>    <descriptorRefs>    <descriptorRef>jar-with-dependencies</descriptorRef>    </descriptorRefs>    <archive>    <manifest>    <mainClass>com.book.test.HelloWorld</mainClass>    </manifest>    </archive>    </configuration>    <executions>    <execution>    <id>make-assembly</id>    <phase>package</phase>    <goals>    <goal>assembly</goal>    </goals>    </execution>    </executions>    </plugin></plugins></build>
</project>

?java ?-javaagent:E:\worktest\MyAgent\target\MyAgent-1.0-jar-with-dependencies.jar -jar E:\worktest\Test\target\Test-1.0-SNAPSHOT.jar com.book.test.HelloWorld

?

執行：

java ?-javaagent:E:\worktest\MyAgent\target\MyAgent-1.0-jar-with-dependencies.jar -jar E:\worktest\Test\target\Test-1.0-SNAPSHOT.jar com.book.test.HelloWorld

注意不在pom設置默認主類可以用 java -cp啟動

參考：https://github.com/liuzhengyang/javaagent-example

https://blog.csdn.net/catoop/article/details/51034739?

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