【实战教程】使用自定义注解实现分布式锁

前言一、设计说明二、代码示例

1.自定义注解2.统一的请求入参对象3.AOP处理4.请求示例

分布式锁应该是日常工作中常见的一种需求，本文将演示如何通过注解的方式，快速实现分布式锁的功能。

分布式锁的简单实现可以借助Redis来完成，加锁时直接利用SET_IF_ABSENT来控制，如果SET成功则表示加锁成功，如果已存在表示业务流程还在锁定中，则直接返回，最后流程处理完之后，将KEY值删除即可。

import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;

@Target(value = ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface RedisDistributedLock {


    
    String name() default "";

    
    String field() default "";
    
    
    long expiration();

    
    Class type();

}

可根据自身公司实际情况修改

@Data
public class RequestData {

    private Header header;

    private T body;

}

@Data
public class Header {

    private String token;

}

@Data
public class Order {

    String orderId;

}

import com.springboot.micrometer.annotation.RedisDistributedLock;
import com.springboot.micrometer.entity.RequestData;
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.data.redis.connection.RedisStringCommands;
import org.springframework.data.redis.core.RedisCallback;
import org.springframework.data.redis.core.RedisTemplate;
import org.springframework.data.redis.core.types.Expiration;
import org.springframework.lang.NonNull;
import org.springframework.stereotype.Component;

import javax.annotation.Resource;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.Map;


@Aspect
@Component
public class RedisDistributedLockAspect {

    @Resource
    private RedisTemplate redisTemplate;


    @Pointcut("@annotation(com.springboot.micrometer.annotation.RedisDistributedLock)")
    public void redisDistributedLock() {
    }


    @Around("redisDistributedLock()")
    public Object methodAround(ProceedingJoinPoint joinPoint) throws Throwable {
        MethodSignature signature = (MethodSignature) joinPoint.getSignature();
        Method method = signature.getMethod();
        RedisDistributedLock redisDistributedLock = method.getAnnotation(RedisDistributedLock.class);

        String field = redisDistributedLock.field();
        String name = redisDistributedLock.name();
        long expiration = redisDistributedLock.expiration();
        Class clazzType = redisDistributedLock.type();

        String fieldValue;

        Object object = clazzType.newInstance();
        Map paramValue = AopUtils.getParamValue(joinPoint);
        if (object instanceof String) {
            fieldValue = (String) paramValue.get(name);
        } else if (object instanceof RequestData) {
            RequestData requestData = (RequestData) paramValue.get(name);
            fieldValue = String.valueOf(AopUtils.getFieldValue(requestData.getBody(), field));
        } else {
            throw new IllegalArgumentException("不支持的参数类型");
        }
        if (lock(fieldValue, fieldValue, expiration)) {
            try {
                return joinPoint.proceed();
            } finally {
                unlock(fieldValue);
            }
        }
        return "重复请求";

    }
    
    public void unlock(String key) {
        redisTemplate.delete(key);
    }

    public boolean lock(@NonNull String key, String value, @NonNull long timeout) {
        return redisTemplate.execute((RedisCallback) connection -> connection.set(key.getBytes(), value.getBytes(), Expiration.seconds(timeout), RedisStringCommands.SetOption.SET_IF_ABSENT));
    }


}

import com.springboot.micrometer.annotation.RedisDistributedLock;
import com.springboot.micrometer.entity.Order;
import com.springboot.micrometer.entity.RequestData;
import org.springframework.web.bind.annotation.RequestBody;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/distribute")
public class DistributedLockController {

    @RedisDistributedLock(field = "orderId", name = "order", expiration = 10, type = RequestData.class)
    @RequestMapping("/query")
    public String query(@RequestBody RequestData order) {
        return "success";
    }

}