java一个切面如何作用做个注解

import org.aspectj.lang.ProceedingJoinPoint;
import org.aspectj.lang.annotation.Around;
import org.aspectj.lang.annotation.Aspect;
import org.aspectj.lang.annotation.Pointcut;
import org.aspectj.lang.reflect.MethodSignature;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import cn.dev33.satoken.strategy.SaStrategy;
import cn.dev33.satoken.util.SaTokenConsts;

/**
 * sa-token 基于 Spring Aop 的注解鉴权
 * 
 * @author kong
 */
@Aspect
@Component
@Order(SaTokenConsts.ASSEMBLY_ORDER)
public class SaCheckAspect {
   
   /**
    * 构建
    */
   public SaCheckAspect() {
   }

   /**
    * 定义AOP签名 (切入所有使用sa-token鉴权注解的方法)
    */
   public static final String POINTCUT_SIGN = 
         "@within(cn.dev33.satoken.annotation.SaCheckLogin) || @annotation(cn.dev33.satoken.annotation.SaCheckLogin) || "
         + "@within(cn.dev33.satoken.annotation.SaCheckRole) || @annotation(cn.dev33.satoken.annotation.SaCheckRole) || "
         + "@within(cn.dev33.satoken.annotation.SaCheckPermission) || @annotation(cn.dev33.satoken.annotation.SaCheckPermission) || "
         + "@within(cn.dev33.satoken.annotation.SaCheckSafe) || @annotation(cn.dev33.satoken.annotation.SaCheckSafe) || "
         + "@within(cn.dev33.satoken.annotation.SaCheckBasic) || @annotation(cn.dev33.satoken.annotation.SaCheckBasic)";

   /**
    * 声明AOP签名
    */
   @Pointcut(POINTCUT_SIGN)
   public void pointcut() {
   }

   /**
    * 环绕切入
    * 
    * @param joinPoint 切面对象
    * @return 底层方法执行后的返回值
    * @throws Throwable 底层方法抛出的异常
    */
   @Around("pointcut()")
   public Object around(ProceedingJoinPoint joinPoint) throws Throwable {
      
      // 注解鉴权
      MethodSignature signature = (MethodSignature) joinPoint.getSignature();
      SaStrategy.me.checkMethodAnnotation.accept(signature.getMethod());

      try {
         // 执行原有逻辑
         Object obj = joinPoint.proceed();
         return obj;
      } catch (Throwable e) {
         throw e;
      }
   }

}