bytebuddy1

gist.java

public class Agent3 {

  public static void main(String[] args) {
    premain("", ByteBuddyAgent.installOnOpenJDK());
    Service service = new Service();
    System.out.println(service);
  }

  public static void premain(String arguments, Instrumentation instrumentation) {
    // System.out.println(Service.class.getCanonicalName());
    new AgentBuilder.Default()
      .rebase(isAnnotatedWith(ToString.class))
      .transform(new AgentBuilder.Transformer() {
        @Override
        public DynamicType.Builder transform(DynamicType.Builder builder,
                                             TypeDescription typeDescription) {
          return builder.method(named("toString"))
            .intercept(FixedValue.value("transformed"));
        }
      }).installOn(instrumentation);
  }

  public @interface ToString { }

  @ToString
  public static class Service {
    public void execute() {
      System.out.println("execute");
    }
  }
}