如何获取方法上声明的注解

news2025/1/24 1:34:06

开发过程当中部分场景需要获取到方法或类上的注解，但是经常会有无法渠道注解的情况，这种情况很可能是该注解所在的类是一个代理类，比如被AOP动态代理【注意：通过】。本文以CGLIB为例，说明为什么无法取到方法或类上的注解，还有如何取到注解。

如果是增强的对象，比如JDK动态代理和CGLIB动态代理。因为CGLIB动态代理生成了一个新的继承了动态

原因是：

1.被增强的类

package com.changshin.annotation;

import java.lang.annotation.*;

@Retention(RetentionPolicy.RUNTIME)
@Target(ElementType.METHOD)
@Documented
public @interface WhiteList {
}

package com.changshin.component;

import lombok.extern.slf4j.Slf4j;
import org.aspectj.lang.annotation.*;
import org.springframework.stereotype.Component;

@Component
@Aspect
@Slf4j
public class WhiteListAspect {

    @Pointcut("@annotation(com.changshin.annotation.WhiteList)")
    public void whiteList(){
        log.info("空实现");
    }

    @Before("whiteList()")
    public void start(){
        log.info("对客户白名单进行校验1");
    }

    @AfterReturning("whiteList()")
    public void end(){
        log.info("对客户白名单进行校验2");
    }

}

package com.changshin.web;

import com.changshin.annotation.WhiteList;
import com.changshin.entity.dto.request.UserInfoRequest;
import com.changshin.entity.dto.response.UserInfoResponse;
import com.changshin.lock.BsnService;
import com.changshin.lock.BusinessLockEnum;
import com.changshin.lock.BusinessLockVO;
import com.changshin.lock.LockService;
import com.changshin.service.UserService;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.BeanFactoryUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.util.ClassUtils;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RestController;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;

@RestController
public class UserApi {
    private static final Logger log = LoggerFactory.getLogger(UserApi.class);

    @Autowired
    private UserService userService;

    @Autowired
    private LockService lockService;

    @Autowired
    private BsnService bsnService;

    @Autowired
    private ApplicationContext applicationContext;

    @PostMapping(value = "user/queryUserName")
    public UserInfoResponse queryUserNameById(@RequestBody UserInfoRequest request){
        log.info("查询用户姓名请求参数",request);
        String[] beanNames = BeanFactoryUtils.beanNamesForTypeIncludingAncestors(applicationContext,UserService.class);
        Class<?> userServiceBean = applicationContext.getType(beanNames[0]);
        Method[] method1s = userServiceBean.getMethods();
        for (Method method:method1s) {
            if (method.isAnnotationPresent(WhiteList.class)){
                System.out.println("userServiceBean111");
            }
        }
        Class<?> userServiceBeanTarget = null;
        //获取代理类代理的目标类
        if(!Proxy.isProxyClass(userServiceBean)){
            userServiceBeanTarget = ClassUtils.getUserClass(userServiceBean);
        }
        Method[] method2s = userServiceBeanTarget.getMethods();
        for (Method method:method2s) {
            if (method.isAnnotationPresent(WhiteList.class)){
                System.out.println("userServiceBeanTarget222");
            }
        }
        return null;
    }
}

发现：

1.userServiceBean是userService进行CGLIB增强后的实例，非userService类型的

2.userServiceBeanTarget是userService类型的实例。