简介

我们在文章《Spring AOP与AspectJ的对比及应用》介绍了AOP的使用，这篇文章讲解一下AOP与注解的整合，通过注解来使用AOP，会非常方便。为了简便，我们还是来实现一个计时的功能。

整合过程

首先创建一个注解：

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
public @interface PkslowLogTime {
}

然后在一个Service中使用注解：

@Service
@Slf4j
public class TestService {
    @PkslowLogTime
    public void fetchData() {
        log.info("fetchData");
        try {
            Thread.sleep(500);
        } catch (InterruptedException e) {
            throw new RuntimeException(e);
        }
    }
}

这个Service的方法会在Controller中调用：

@GetMapping("/hello")
public String hello() {
  log.info("------hello() start---");
  test();
  staticTest();
  testService.fetchData();
  log.info("------hello() end---");
  return "Hello, pkslow.";
}

接着是关键一步，我们要实现切面，来找到注解并实现对应功能：

@Aspect
@Component
@Slf4j
public class PkslowLogTimeAspect {
    @Around("@annotation(com.pkslow.springboot.aop.PkslowLogTime) && execution(* *(..))")
    public Object doAround(ProceedingJoinPoint joinPoint) throws Throwable {
        log.info("------PkslowLogTime doAround start------");
        MethodSignature methodSignature = (MethodSignature) joinPoint.getSignature();
        // Get intercepted method details
        String className = methodSignature.getDeclaringType().getSimpleName();
        String methodName = methodSignature.getName();
        // Measure method execution time
        StopWatch stopWatch = new StopWatch(className + "->" + methodName);
        stopWatch.start(methodName);
        Object result = joinPoint.proceed();
        stopWatch.stop();
        // Log method execution time
        log.info(stopWatch.prettyPrint());
        log.info("------PkslowLogTime doAround end------");
        return result;
    }
}

@Around("@annotation(com.pkslow.springboot.aop.PkslowLogTime) && execution(* *(..))")这个表达式很关键，如果不对，将无法正确识别；还有可能出现多次调用的情况。多次调用的情况可以参考：Stackoverflow

这里使用了Spring的StopWatch来计时。

测试

通过maven build包：

$ mvn clean package

日志可以看到有对应的织入信息：

[INFO] Join point 'method-execution(java.lang.String com.pkslow.springboot.controller.TestController.hello())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:22) advised by around advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
[INFO] Join point 'method-execution(java.lang.String com.pkslow.springboot.controller.TestController.hello())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:22) advised by before advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
[INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.test())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:31) advised by around advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
[INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.test())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:31) advised by before advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
[INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.staticTest())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:37) advised by around advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
[INFO] Join point 'method-execution(void com.pkslow.springboot.controller.TestController.staticTest())' in Type 'com.pkslow.springboot.controller.TestController' (TestController.java:37) advised by before advice from 'com.pkslow.springboot.aop.ControllerAspect' (ControllerAspect.class(from ControllerAspect.java))
[INFO] Join point 'method-execution(void com.pkslow.springboot.service.TestService.fetchData())' in Type 'com.pkslow.springboot.service.TestService' (TestService.java:12) advised by around advice from 'com.pkslow.springboot.aop.PkslowLogTimeAspect' (PkslowLogTimeAspect.class(from PkslowLogTimeAspect.java))

启动应用后访问接口，日志如下：

总结

通过注解可以实现很多功能，也非常方便。而且注解还可以添加参数，组合使用更完美了。

代码请看GitHub: https://github.com/LarryDpk/pkslow-samples