java-Annotation 反射

Java注解与AOP实践

最新推荐文章于 2022-12-28 11:41:00 发布

最新推荐文章于 2022-12-28 11:41:00 发布 · 217 阅读

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#Annotation #注解 #反射

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本文介绍如何使用Java注解结合AOP实现方法级别的日志记录功能。通过@Aspect注解定义切面，并利用@Around注解进行环绕通知，实现了在目标方法执行前后打印日志的功能。此外还展示了如何通过反射获取注解信息。

java中的注解也可以反射

切面注解：


@Aspect
public class LogAspect {

	@Around(value = "@annotation(com.gym.Monitor)",argNames = "ssss")
     public Object log(ProceedingJoinPoint pjp) throws Throwable{
    	 System.out.println("BEGIN-------------------" +pjp+"-------------------");
    	 Object obj =  pjp.proceed();
    	 System.out.println("END-------------------" +pjp+"-------------------"+obj);
    	 return obj;
     }
}

测试：


@Test
	public void testAspectJAnnotation() throws Exception{
		LogAspect la = new LogAspect();
		Method method = la.getClass().getMethod("log", ProceedingJoinPoint.class);

		Annotation annotation = method.getAnnotation(Around.class);

		String s = resolveExpression(annotation);
		System.out.println(s);
		Object obj = annotation.getClass().getMethod("argNames").invoke(annotation);
		System.out.println(obj);
	}



	private String resolveExpression(Annotation annotation) throws Exception {
		String[] EXPRESSION_PROPERTIES = new String[] {"value", "pointcut"};
		String expression = null;
		for (String methodName : EXPRESSION_PROPERTIES) {
			Method method;
			try {
				method = annotation.getClass().getDeclaredMethod(methodName);
			}
			catch (NoSuchMethodException ex) {
				method = null;
			}
			if (method != null) {
				String candidate = (String) method.invoke(annotation);
				if (StringUtils.hasText(candidate)) {
					expression = candidate;
				}
			}
		}
		return expression;
	}