springboot中带aop的bytebuddy不起作用

Question

我尝试使用bytebuddy在springboot中实现aop。代码如下：

package klordy.learning.annotation;
@Target(METHOD)
@Retention(RUNTIME)
@Documented
public @interface CostTime {
}

package klordy.learning.agent;
public class Agent {
private static Agent instance = new Agent();
    private Logger logger = LoggerFactory.getLogger(Agent.class);
    private Agent() {}
    public static Agent getInstance(){ return instance; }
    public void install() {
        ByteBuddyAgent.install();
        AgentBuilder.Listener listener = new AgentBuilder.Listener() {
            // do nothing
            ...
        };

        new AgentBuilder.Default()
                .type(ElementMatchers.nameStartsWith("klordy.learning"))
                .transform((builder, typeDescription, classLoader, module) ->
                        builder.visit(Advice.to(TimeAdvice.class).on(ElementMatchers.isAnnotatedWith(named("klordy.learning.annotation.CostTime")))))
                .with(listener)
                // *** added as supposed, but still seems not work.
                .with(AgentBuilder.RedefinitionStrategy.RETRANSFORMATION)
                .installOnByteBuddyAgent();
         logger.info("byte buddy modification done.");
     }
}

public class TimeAdvice {
    @Advice.OnMethodEnter
    static long enter(@Advice.AllArguments Object args[], @Advice.Origin Method method){
        return System.currentTimeMillis();
    }

    @Advice.OnMethodExit
    static void exit(@Advice.Enter long startTime,
                     @Advice.Return(typing = Assigner.Typing.DYNAMIC) Object result,
                     @Advice.Origin Method method,
                     @Advice.Thrown Throwable throwable){
        if(throwable != null){
            System.out.println("error func " + System.currentTimeMillis());
        }else {
            System.out.println("func takes " + (System.currentTimeMillis() - startTime));
        }
    }
}

springboot的监听器如下：

public class AppEnvListener implements ApplicationListener<ApplicationEnvironmentPreparedEvent> {
    private Logger logger = LoggerFactory.getLogger(AppEnvListener.class);
    @Override
    public void onApplicationEvent(ApplicationEnvironmentPreparedEvent applicationEnvironmentPreparedEvent) {
        Agent.getInstance().install();
        logger.info("finished byte buddy installation.");
    }
}

最后，在springboot启动中注册侦听器：

@SpringBootApplication
@ComponentScan(basePackages = "klordy.learning")
public class SpringBootDemoApplication {

    public static void main(String[] args) {
       SpringApplication application = new SpringApplication(SpringBootDemoApplication.class);
       // register listener
       application.addListeners(new AppEnvListener());
       application.run(args);
    }
}

当我启动应用程序时，调试记录器显示良好。然而，当请求被处理时，aop不起作用。我做错了什么？我很困惑。。。

Answer 1

您所讨论的类可能已经加载。

设置。在代理配置中使用（RetransformationStrategy.RETRANSFORM），或者在main方法中加载Spring之前安装代理。

Answer 2

好吧，我想我通过用Spring Boot重现你的情况找到了你的问题。不过，没有Spring也会发生。基本上你就碰到这个问题了。

因此，如果您将建议修改为@advice。在methodexit（onThrowable=Throwable.class）上，您应该很好。您还应该添加。disableClassFormatChanges（）发送给您的代理，顺便说一句。它有助于避免重新传输以前加载的类时出现问题。JVM要求它们在结构上不被改变。

我怎么知道发生了什么？我启动了控制台登录ByteBuddy。之前我用过你的监听器，让它记录每一个动作，这样我就可以看到BB实际上被触发了。但是BB日志确实显示了由于错误使用@Advice而导致的异常。抛出（在通知注释中没有onThrowable=Throwable.class）。

public void install() {
  ByteBuddyAgent.install();
  new AgentBuilder.Default()
    .disableClassFormatChanges()
    .with(RETRANSFORMATION)
    .with(AgentBuilder.RedefinitionStrategy.Listener.StreamWriting.toSystemError())
    .with(AgentBuilder.Listener.StreamWriting.toSystemError().withTransformationsOnly())
    .with(AgentBuilder.InstallationListener.StreamWriting.toSystemError())
    .type(ElementMatchers.nameStartsWith("klordy.learning"))
    .transform((builder, typeDescription, classLoader, module) ->
      builder.visit(
        Advice
          .to(TimeAdvice.class)
          .on(isAnnotatedWith(named("klordy.learning.annotation.CostTime")))
      )
    )
    .installOnByteBuddyAgent();
  logger.info("byte buddy modification done.");
}