Is it possible to rebase System.currentTimeMillis

Hi,

I’ve spent a long time trying to figure out how to rebase System.currentTimeMillis. What I wanted is override this bootstrap class’s method with another customized clock, which means I still need to call the original System.currentTimeMillis to get the actual time and have some transformation on it. I have already successfully redefine the method with following code on Java agent mode:-

final ByteBuddy byteBuddy = new ByteBuddy().with(Implementation.Context.Disabled.Factory.INSTANCE);
new AgentBuilder.Default()
	.enableNativeMethodPrefix("test_native")
	.with(byteBuddy)
	.with(AgentBuilder.InitializationStrategy.NoOp.INSTANCE)
	.with(AgentBuilder.RedefinitionStrategy.REDEFINITION)
	.with(AgentBuilder.TypeStrategy.Default.REDEFINE)
	.ignore(none())
	.type(ElementMatchers.named("java.lang.System"))
	.transform(new AgentBuilder.Transformer() {
		@Override
		public DynamicType.Builder<?> transform(DynamicType.Builder<?> builder, TypeDescription typeDescription, ClassLoader classLoader, JavaModule module) {
					return builder.method(ElementMatchers.named("currentTimeMillis")).intercept(
						MethodDelegation.to(SystemTimeInterceptor.class));
				}
			}).installOn(inst);

Can you please kindly advise if it is ever possible to rebase that method? Any suggestion will be appreciated. Thanks!

[huangyoje]

Just ran into the same problem, put my solution here, hoping to help others. If you need redefine System. currentTimeMillis(), there is another way to get the real time.

   Process process = Runtime.getRuntime().exec("date +%s");
   BufferedReader reader = new BufferedReader(new InputStreamReader(process.getInputStream()));
   System.out.println(reader.readLine());

[RockyLOMO]

My solution is to call nanoTime and currentTimeMillis once each before injecting and save the result, so that the current time can be calculated using

 (System.nanoTime() - savedNanoTime) / 1000000L + savedCurrentTimeMillis

, and then use ntp synchronized time to calculate the offset and change the savedCurrentTimeMillis value.

 (System.nanoTime() - savedNanoTime) / 1000000L + savedCurrentTimeMillis + ntpOffset