java - Spring AOP : aspect @Around doesn't work

Question

我使用 Spring Boot 和 Spring Initializr 制作了一个简单的 Web 应用程序，并尝试编写 @Aspect 与 @左右建议。

当我添加自定义注释时 @RetryOnFailure 到 Controller 的端点方法 - 它可以工作，但是当我将此注释添加到 Controller 端点执行的 Controller 方法时 - 它不起作用。我花了很多时间来了解这种行为的原因，但没有任何结果。所以请帮忙。

项目地址:https://github.com/zalizko/spring-aop-playground

@Aspect
@Component
public final class MethodRepeater {

    @Around("execution(* *(..)) && @annotation(RetryOnFailure)")
    public Object wrap(final ProceedingJoinPoint joinPoint) throws Throwable {
        // code is here
    }
}

所以，我的目标是:

@RequestMapping
public String index() {
    inTry();
    return "OK";
}


@RetryOnFailure(attempts = 3, delay = 2, unit = TimeUnit.SECONDS)
public void inTry() {
    throw new RuntimeException("Exception in try " + ++counter);
}

Answer 1

您犯了一个典型的 Spring AOP 初学者错误:您忘记了基于代理的 AOP 仅在代理方法从外部调用时才有效，而不是通过 this (避免代理)。但是内部电话inTry()与 this.inTry() 相同.因此，方面永远不会触发 inTry你必须像这样重新排列你的代码:

package spring.aop;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.concurrent.TimeUnit;

@RestController("/")
public class HomeController {

    static int counter = 0;

    @RequestMapping
    @RetryOnFailure(attempts = 3, delay = 2, unit = TimeUnit.SECONDS)
    public String index() {
        throw new RuntimeException("Exception in try " + ++counter);
    }
}

我也稍微改变了外观，以便

避免反射并将注释直接通过 @annotation() 绑定(bind)到通知参数,

当通知被触发时记录连接点和

在尝试 #3 时返回“OK”(只是为了好玩，没有必要)。

package spring.aop;

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.springframework.stereotype.Component;

@Aspect
@Component
public final class MethodRepeater {

    @Around("execution(* spring.aop..*(..)) && @annotation(retryOnFailure)")
    public Object wrap(final ProceedingJoinPoint joinPoint, RetryOnFailure retryOnFailure) throws Throwable {
        System.out.println(joinPoint);
        return proceed(joinPoint, retryOnFailure);
    }

    private Object proceed(ProceedingJoinPoint joinPoint, RetryOnFailure retryOnFailure) throws Throwable {
        int attempt = 1;
        while (true) {
            try {
                return joinPoint.proceed();
            } catch (final Throwable ex) {
                System.out.println("Try #" + attempt + " failed: " + ex);
                if (++attempt >= retryOnFailure.attempts())
                    return "OK";
                if (retryOnFailure.delay() > 0L)
                    retryOnFailure.unit().sleep(retryOnFailure.delay());
            }
        }
    }
}

现在它可以工作了，控制台日志说:

execution(String spring.aop.HomeController.index())
Try #1 failed: java.lang.RuntimeException: Exception in try 1
Try #2 failed: java.lang.RuntimeException: Exception in try 2