BeanPostProcessor實現自定義註解掃描器

       在項目中由於各種需要我們會自定義各種註解，就比如像Redis的訂閱和發佈，那麼我們就會有查找所有使用了指定註解的方法的需求，並對這些方法做一些統一的操作，把這個需求封裝到一個註解掃描器的抽象類工具中，不同的自定義註解去各自實現，這樣就會方便很多

         這裏擴展了Spring的後置處理器BeanPostProcessor類，在Bean容器實例化、依賴注入並初始化完畢時執行註解掃描操作

/**
 * 註解方法通用基礎VO
 */
public class BeanMethod {
  private Object bean;
  private Method method;

  public BeanMethod(Object bean, Method method) {
    this.bean = bean;
    this.method = method;
  }

  public Object getBean() {
    return bean;
  }

  public void setBean(Object bean) {
    this.bean = bean;
  }

  public Method getMethod() {
    return method;
  }

  public void setMethod(Method method) {
    this.method = method;
  }
}

 

/**
 * 通用註解掃描器
 */
public abstract class BaseAnnotationScanner implements BeanPostProcessor {
  private static final Log log = LogFactory.getLog(GeiBaseAnnotationScanner.class);

  //所有的註解
  private List<BeanMethod> methodList = new ArrayList<>();

  protected abstract Class findAnnotationType();

  @Override
  public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
    return bean;
  }

  @Override
  public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
    initMethodByAnnotation(bean, findAnnotationType());
    return bean;
  }

  /**
   * 反射查找類中特定註解的方法
   */
  private void initMethodByAnnotation(Object bean, Class annotationType) {
    Method[] methods = ReflectionUtils.getAllDeclaredMethods(bean.getClass());
    if (null != methods ) {
      for (Method method : methods) {
        Annotation annotation = AnnotationUtils.findAnnotation(method, annotationType);
        if (null == annotation) {
          continue;
        }
        methodList.add(new BeanMethod(bean,method));
      }
    }
  }

  public List<BeanMethod> getMethods() {
    return methodList;
  }

  public void setMethods(List<BeanMethod> methods) {
    this.methods = methodList;
  }
}

具體應用如下，繼承基礎掃描器，指定註解類型即可

/**
 * Redis訂閱註解掃描器
 */
@Component
public class RedisSubscriberAnnotationScanner extends BaseAnnotationScanner {

  @Override
  protected Class findAnnotationType() {
    return RedisSubscriber.class;
  }

}