+ demo-core 基础类
+ demo-app 演示应用，循环调用Greeting.sayHello()
+ demo-agent 一个简单的Java Agent，输出所有JVM加载的类列表
+ demo-asm 一个Java Agent，通过ASM对Greeting类进行增强
+ demo-javaassist 一个Java Agent，通过Javassist对Greeting类进行增强
+ demo-bytebuddy 一个Java Agent，通过Bytebuddy对Greeting类进行增强
+ demo-cglib 通过cglib对Greeting类进行增强

mvn clean package

java -javaagent:./demo-agent/target/agent-agent.jar -jar ./demo-app/target/demo-app.jar

loading agent..
agent has been loaded.
transforming class = java/lang/invoke/MethodHandleImpl
transforming class = java/lang/invoke/MethodHandleImpl$1
transforming class = java/lang/invoke/MethodHandleImpl$2
transforming class = java/util/function/Function
transforming class = java/lang/invoke/MethodHandleImpl$3
transforming class = java/lang/invoke/MethodHandleImpl$4
transforming class = java/lang/ClassValue

public class Greeting {

    public String sayHello() {
        String hello = "hello,world";
        System.out.println(hello);
        return hello;
    }

}

begin of sayhello().
hello,world
end of sayhello().

java -javaagent:./demo-asm/target/agent-asm.jar -jar ./demo-app/target/demo-app.jar

count = 1
begin of sayhello().
hello,world
end of sayhello().

count = 2
begin of sayhello().
hello,world
end of sayhello().

java -javaagent:./demo-javaassist/target/agent-jassist.jar -jar ./demo-app/target/demo-app.jar

count = 1
begin of sayhello()
hello,world
end of sayhello()

count = 2
begin of sayhello()
hello,world
end of sayhello()

java -javaagent:./demo-bytebuddy/target/agent-buddy.jar -jar ./demo-app/target/demo-app.jar

[main][INFO] loading agent..
[main][INFO] agent has been loaded.

count = 1
[main][INFO] transforming com.pphh.demo.api.Greeting...
start of method()
hello,world
end of method()

count = 2
start of method()
hello,world
end of method()