Find method level custom annotation in a Spring context

Question

All I wanted to find out was "all the class/methods in Spring beans which are annotated as @Versioned".

I created my custom annotation as,

@Target({ElementType.METHOD, ElementType.TYPE})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface Versioned {
    .....
}

This annotation works perfectly when I use Java reflection to find methods as:

for(Method m: obj.getClass().getMethods()){
    if(m.isAnnotationPresent(Versioned.class)){
        .... // Do something
    }

But it does not work when I access Spring beans and try similar check:

public class VersionScanner implements ApplicationContextAware{
    public void setApplicationContext(ApplicationContext applicationContext){
        for(String beanName: applicationContext.getBeanDefinitionNames()){
            for(Method m: applicationContext.getBean(beanName).getClass().getDeclaredMethods()){
                if(m.isAnnotationPresent(Versioned.class){
                    // This is not WORKING as expected for any beans with method annotated
                }
            }
        }
    }
}

In fact, this code does find other annotations such as @RequestMapping. I am not sure what I am doing wrong with my custom annotation.

Answer 1

Going through your code, I figured out that you are using Spring AOP with CGLIB Proxying. Due to which your classes (which have methods annotated with @Versioned ) are being proxied.

I have tested this solution with your code base.

Use the following code, and it should resolve your issue. Look for more options below the code snippet:

@Configuration
public class VersionScanner implements ApplicationContextAware {

    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {

        for (String beanName : applicationContext.getBeanDefinitionNames()) {
            Object obj = applicationContext.getBean(beanName);
            /*
             * As you are using AOP check for AOP proxying. If you are proxying with Spring CGLIB (not via Spring AOP)
             * Use org.springframework.cglib.proxy.Proxy#isProxyClass to detect proxy If you are proxying using JDK
             * Proxy use java.lang.reflect.Proxy#isProxyClass
             */
            Class<?> objClz = obj.getClass();
            if (org.springframework.aop.support.AopUtils.isAopProxy(obj)) {

                objClz = org.springframework.aop.support.AopUtils.getTargetClass(obj);
            }

            for (Method m : objClz.getDeclaredMethods()) {
                if (m.isAnnotationPresent(Versioned.class)) {
                    //Should give you expected results
                }
            }
        }
    }
}

To detect a proxy class:

• For Spring AOP proxy using any proxying mechanism use org.springframework.aop.support.AopUtils#isAoPProxy
• If you are proxying with Spring CGLIB (not via Spring AOP), use org.springframework.cglib.proxy.Proxy#isProxyClass
• If you are proxying using JDK Proxy, use java.lang.reflect.Proxy#isProxyClass

I have just written one if condition which is sufficient in your case; but in case multiple proxying utilities are used, multiple if-else conditions will have to be written based on the information above.