是否可以从 Bean 内部访问 Bean 方法的注释？

Question

假设我正在使用以下代码初始化 bean：

@Configuration 
MyConfig {
    @Bean
    @MyAnnotation // how to know this from bean constructor or method?
    MyBean myBean() {
       MyBean ans = new MyBean();
       /// setup ans
       return ans;
    }
}

我可以从 bean 构造函数或 bean 的方法中知道一些关于@MyAnnotation注释的信息吗？

不是从myBean()方法内部，这是显而易见的。

Answer 1

好吧，这可能不是最好甚至正确的方法，但我的第一个猜测是使用当前的堆栈跟踪，它似乎对我有用：

package yourpackage;
import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
public class AspectJRawTest {
    public static void main(String[] args) {
        System.out.println("custom annotation playground");
        ISomething something = new SomethingImpl();
        something.annotatedMethod();
        something.notAnnotatedMethod();
    }
}
interface ISomething {
    void annotatedMethod();
    void notAnnotatedMethod();
}
class SomethingImpl implements ISomething {
    @MyCustomAnnotation
    public void annotatedMethod() {
        System.out.println("I am annotated and something must be printed by an advice above.");
        CalledFromAnnotatedMethod ca = new CalledFromAnnotatedMethod();
    }
    public void notAnnotatedMethod() {
        System.out.println("I am not annotated and I will not get any special treatment.");
        CalledFromAnnotatedMethod ca = new CalledFromAnnotatedMethod();
    }
}
/**
 * Imagine this is your bean which needs to know if any annotations affected it's construction
 */
class CalledFromAnnotatedMethod {
    CalledFromAnnotatedMethod() {
        List<Annotation> ants = new ArrayList<Annotation>();
        for (StackTraceElement elt : Thread.currentThread().getStackTrace()) {
            try {
                Method m = Class.forName(elt.getClassName()).getMethod(elt.getMethodName());
                ants.addAll(Arrays.asList(m.getAnnotations()));
            } catch (ClassNotFoundException ignored) {
            } catch (NoSuchMethodException ignored) {
            }
        }
        System.out.println(ants);
    }
}

输出清楚地表明，当从注释方法调用对象构造函数时，我可以访问对象的构造函数中的注释：

custom annotation playground
I am annotated and something must be printed by an advice above.
[@yourpackage.MyCustomAnnotation(isRun=true)]
I am not annotated and I will not get any special treatment.
[]