java 解密 class
run command java -javaagent:java-agent.jar="Hi" -jar client.jar

├── java-agent.jar
├── META-INF
│   └── MANIFEST.MF
└── org
    └── bougainvilleas
        └── ilj
            └── agent
                ├── JavaAgent.class
                ├── JavaAgent.java
                ├── JavaClassFileTransformer.class
                └── JavaClassFileTransformer.java

手动 创建 META-INF/MANIFEST.MF 注意 MANIFEST.MF 需要以空行结尾

Manifest-Version: 1.0
Premain-Class: org.bougainvilleas.ilj.agent.JavaAgent

手动编译 javac org/bougainvilleas/ilj/agent/*.java
手动打包 jar -cvf0M java-agent.jar META-INF/MANIFEST.MF org/bougainvilleas/ilj/agent/*.class

-0 表示压缩
-M 表示不自动创建 MANIFEST.MF

利用 gradle build.gradle 添加 Premain-Class

jar.manifest {
    attributes('Premain-Class':"org.bougainvilleas.ilj.agent.JavaAgent")
}