如何从@ Advice.OnMethodExit中的premain方法获取arg？

Question

public static void premain(String arg, Instrumentation instrumentation) {
        System.out.println("Agent for time measure:" + arg);
}

我想通过以下方法获取arg，否则不使用arg。最好，在OnMethodExit方法中获取arg。

public class TimerAdvice3 {

    @Advice.OnMethodEnter
    static long enter(@Advice.Origin String method, @Advice.AllArguments Object[] args) throws Exception {
        HttpUriRequest httpUriRequest = (HttpUriRequest) args[1];
        System.out.println(httpUriRequest.toString());
        long start = System.currentTimeMillis();
        return start;
    }

    @Advice.OnMethodExit
    static void exit(@Advice.Origin String method, @Advice.Enter long start) throws Exception {
        long end = System.currentTimeMillis();
        System.out.println("拦截======》" + method + " took " + (end - start) + " milliseconds ");
    }

}

Answer 1

您是否尝试应用所写的建议？您需要为此使用AgentBuilder API：

new AgentBuilder.Default()
  .type(...)
  .transform((builder, type, classLoader, module) -> builder.visit(Advice
     .to(TimerAdvice.class)
     .on(...))
  .installOn(instrumentation);

如果您只想阅读@Advice.Argument(0)，则可以使用HttpUriRequest。