备忘4：通过切面+自定义注解，优雅的实现Lock锁

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package com.alex.easyexcel.lock.annotation;

import java.lang.annotation.*;

@Target({ElementType.PARAMETER, ElementType.METHOD})
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ServiceLock {
    String description() default "";
}

package com.alex.easyexcel.lock.aspect;

import lombok.extern.slf4j.Slf4j;
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.springframework.context.annotation.Scope;
import org.springframework.core.annotation.Order;
import org.springframework.stereotype.Component;

import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

@Slf4j
@Component
@Scope
@Aspect
@Order(1) //order越小越是最先执行，但更重要的是最先执行的最后结束
public class LockAspect {
    /**
     * 思考：为什么不用synchronized
     * service 默认是单例的，并发下lock只有一个实例
     */
    private static Lock lock = new ReentrantLock(true); // 互斥锁 参数默认false，不公平锁

    // Service层切点     用于记录错误日志
    @Pointcut("@annotation(com.alex.easyexcel.lock.annotation.ServiceLock)")
    public void lockAspect() {

    }

    @Around("lockAspect()")
    public Object around(ProceedingJoinPoint joinPoint) {
        lock.lock();
        System.out.println("上锁成功！！！！");
        Object obj;
        try {
            obj = joinPoint.proceed();
        } catch (Throwable e) {
            e.printStackTrace();
            throw new RuntimeException();
        } finally {
            lock.unlock();
            System.out.println("释放锁成功！！！！");
        }
        return obj;
    }
}

package com.alex.easyexcel.lock.controller;

import com.alex.easyexcel.lock.service.LockService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.PostMapping;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.util.Map;

@RestController
@RequestMapping("/lock")
public class LockController {
    @Autowired
    private LockService lockService;

    @PostMapping("/test1")
    private void test1(@RequestBody Map<String, Object> map) {
        lockService.test1(map);
    }
}

package com.alex.easyexcel.lock.service;

import java.util.Map;

public interface LockService {
    void test1(Map<String, Object> map);
}

package com.alex.easyexcel.lock.service.impl;

import com.alex.easyexcel.lock.annotation.ServiceLock;
import com.alex.easyexcel.lock.service.LockService;
import org.springframework.stereotype.Service;
import org.springframework.transaction.annotation.Transactional;

import java.util.Map;

@Service
public class LockServiceImpl implements LockService {

    @ServiceLock
    @Override
    @Transactional(rollbackFor = Exception.class)
    public void test1(Map<String, Object> map) {
        String number = (String) map.get("number");
        Integer n = Integer.parseInt(number);
        int i = 10 / n;
        System.out.println(i);
    }
}

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