一口气说出8种幂等性解决重复提交的方案,面试官懵了!
1.什么是幂等
2.产生原因
3.解决方案
import java.lang.annotation.*; @Target(ElementType.METHOD) @Retention(RetentionPolicy.RUNTIME) @Documented public @interface Resubmit { /** * 延时时间 在延时多久后可以再次提交 * * @return Time unit is one second */ int delaySeconds() default 20; }
import com.google.common.cache.Cache; import com.google.common.cache.CacheBuilder; import lombok.extern.slf4j.Slf4j; import org.apache.commons.codec.digest.DigestUtils; import java.util.Objects; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.ScheduledThreadPoolExecutor; import java.util.concurrent.ThreadPoolExecutor; import java.util.concurrent.TimeUnit; /** * @author lijing * 重复提交锁 */ @Slf4j public final class ResubmitLock { private static final ConcurrentHashMapLOCK_CACHE = new ConcurrentHashMap<>(200); private static final ScheduledThreadPoolExecutor EXECUTOR = new ScheduledThreadPoolExecutor(5, new ThreadPoolExecutor.DiscardPolicy()); // private static final CacheCACHES = CacheBuilder.newBuilder() // 最大缓存 100 个 // .maximumSize(1000) // 设置写缓存后 5 秒钟过期 // .expireAfterWrite(5, TimeUnit.SECONDS) // .build(); private ResubmitLock() { } /** * 静态内部类 单例模式 * * @return */ private static class SingletonInstance { private static final ResubmitLock INSTANCE = new ResubmitLock(); } public static ResubmitLock getInstance() { return SingletonInstance.INSTANCE; } public static String handleKey(String param) { return DigestUtils.md5Hex(param == null ? "" : param); } /** * 加锁 putIfAbsent 是原子操作保证线程安全 * * @param key 对应的key * @param value * @return */ public boolean lock(final String key, Object value) { return Objects.isNull(LOCK_CACHE.putIfAbsent(key, value)); } /** * 延时释放锁 用以控制短时间内的重复提交 * * @param lock 是否需要解锁 * @param key 对应的key * @param delaySeconds 延时时间 */ public void unLock(final boolean lock, final String key, final int delaySeconds) { if (lock) { EXECUTOR.schedule(() -> { LOCK_CACHE.remove(key); }, delaySeconds, TimeUnit.SECONDS); } } }
import com.alibaba.fastjson.JSONObject; import com.cn.xxx.common.annotation.Resubmit; import com.cn.xxx.common.annotation.impl.ResubmitLock; import com.cn.xxx.common.dto.RequestDTO; import com.cn.xxx.common.dto.ResponseDTO; import com.cn.xxx.common.enums.ResponseCode; import lombok.extern.log4j.Log4j; import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.reflect.MethodSignature; import org.springframework.stereotype.Component; import java.lang.reflect.Method; /** * @ClassName RequestDataAspect * @Description 数据重复提交校验 * @Author lijing * @Date 2019/05/16 17:05 **/ @Log4j @Aspect @Component public class ResubmitDataAspect { private final static String DATA = "data"; private final static Object PRESENT = new Object(); @Around("@annotation(com.cn.xxx.common.annotation.Resubmit)") public Object handleResubmit(ProceedingJoinPoint joinPoint) throws Throwable { Method method = ((MethodSignature) joinPoint.getSignature()).getMethod(); //获取注解信息 Resubmit annotation = method.getAnnotation(Resubmit.class); int delaySeconds = annotation.delaySeconds(); Object[] pointArgs = joinPoint.getArgs(); String key = ""; //获取第一个参数 Object firstParam = pointArgs[0]; if (firstParam instanceof RequestDTO) { //解析参数 JSONObject requestDTO = JSONObject.parseObject(firstParam.toString()); JSONObject data = JSONObject.parseObject(requestDTO.getString(DATA)); if (data != null) { StringBuffer sb = new StringBuffer(); data.forEach((k, v) -> { sb.append(v); }); //生成加密参数 使用了content_MD5的加密方式 key = ResubmitLock.handleKey(sb.toString()); } } //执行锁 boolean lock = false; try { //设置解锁key lock = ResubmitLock.getInstance().lock(key, PRESENT); if (lock) { //放行 return joinPoint.proceed(); } else { //响应重复提交异常 return new ResponseDTO<>(ResponseCode.REPEAT_SUBMIT_OPERATION_EXCEPTION); } } finally { //设置解锁key和解锁时间 ResubmitLock.getInstance().unLock(lock, key, delaySeconds); } } }
@ApiOperation(value = "保存我的帖子接口", notes = "保存我的帖子接口") @PostMapping("/posts/save") @Resubmit(delaySeconds = 10) public ResponseDTOsaveBbsPosts(@RequestBody @Validated RequestDTOrequestDto) { return bbsPostsBizService.saveBbsPosts(requestDto); }
<dependencies> <dependency> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-starter-webartifactId> dependency> <dependency> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-starter-aopartifactId> dependency> <dependency> <groupId>org.springframework.bootgroupId> <artifactId>spring-boot-starter-data-redisartifactId> dependency> dependencies>
spring.redis.host=localhost spring.redis.port=6379 spring.redis.password=123456
package com.battcn.interceptor; import com.battcn.annotation.CacheLock; import com.battcn.utils.RedisLockHelper; import org.aspectj.lang.ProceedingJoinPoint; import org.aspectj.lang.annotation.Around; import org.aspectj.lang.annotation.Aspect; import org.aspectj.lang.reflect.MethodSignature; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.context.annotation.Configuration; import org.springframework.util.StringUtils; import java.lang.reflect.Method; import java.util.UUID; /** * redis 方案 * * @author Levin * @since 2018/6/12 0012 */ @Aspect @Configuration public class LockMethodInterceptor { @Autowired public LockMethodInterceptor(RedisLockHelper redisLockHelper, CacheKeyGenerator cacheKeyGenerator) { this.redisLockHelper = redisLockHelper; this.cacheKeyGenerator = cacheKeyGenerator; } private final RedisLockHelper redisLockHelper; private final CacheKeyGenerator cacheKeyGenerator; @Around("execution(public * *(..)) && @annotation(com.battcn.annotation.CacheLock)") public Object interceptor(ProceedingJoinPoint pjp) { MethodSignature signature = (MethodSignature) pjp.getSignature(); Method method = signature.getMethod(); CacheLock lock = method.getAnnotation(CacheLock.class); if (StringUtils.isEmpty(lock.prefix())) { throw new RuntimeException("lock key don't null..."); } final String lockKey = cacheKeyGenerator.getLockKey(pjp); String value = UUID.randomUUID().toString(); try { // 假设上锁成功,但是设置过期时间失效,以后拿到的都是 false final boolean success = redisLockHelper.lock(lockKey, value, lock.expire(), lock.timeUnit()); if (!success) { throw new RuntimeException("重复提交"); } try { return pjp.proceed(); } catch (Throwable throwable) { throw new RuntimeException("系统异常"); } } finally { // TODO 如果演示的话需要注释该代码;实际应该放开 redisLockHelper.unlock(lockKey, value); } } }
package com.battcn.utils; import org.springframework.boot.autoconfigure.AutoConfigureAfter; import org.springframework.boot.autoconfigure.data.redis.RedisAutoConfiguration; import org.springframework.context.annotation.Configuration; import org.springframework.data.redis.connection.RedisStringCommands; import org.springframework.data.redis.core.RedisCallback; import org.springframework.data.redis.core.StringRedisTemplate; import org.springframework.data.redis.core.types.Expiration; import org.springframework.util.StringUtils; import java.util.concurrent.Executors; import java.util.concurrent.ScheduledExecutorService; import java.util.concurrent.TimeUnit; import java.util.regex.Pattern; /** * 需要定义成 Bean * * @author Levin * @since 2018/6/15 0015 */ @Configuration @AutoConfigureAfter(RedisAutoConfiguration.class) public class RedisLockHelper { private static final String DELIMITER = "|"; /** * 如果要求比较高可以通过注入的方式分配 */ private static final ScheduledExecutorService EXECUTOR_SERVICE = Executors.newScheduledThreadPool(10); private final StringRedisTemplate stringRedisTemplate; public RedisLockHelper(StringRedisTemplate stringRedisTemplate) { this.stringRedisTemplate = stringRedisTemplate; } /** * 获取锁(存在死锁风险) * * @param lockKey lockKey * @param value value * @param time 超时时间 * @param unit 过期单位 * @return true or false */ public boolean tryLock(final String lockKey, final String value, final long time, final TimeUnit unit) { return stringRedisTemplate.execute((RedisCallback) connection -> connection.set(lockKey.getBytes(), value.getBytes(), Expiration.from(time, unit), RedisStringCommands.SetOption.SET_IF_ABSENT)); } /** * 获取锁 * * @param lockKey lockKey * @param uuid UUID * @param timeout 超时时间 * @param unit 过期单位 * @return true or false */ public boolean lock(String lockKey, final String uuid, long timeout, final TimeUnit unit) { final long milliseconds = Expiration.from(timeout, unit).getExpirationTimeInMilliseconds(); boolean success = stringRedisTemplate.opsForValue().setIfAbsent(lockKey, (System.currentTimeMillis() + milliseconds) + DELIMITER + uuid); if (success) { stringRedisTemplate.expire(lockKey, timeout, TimeUnit.SECONDS); } else { String oldVal = stringRedisTemplate.opsForValue().getAndSet(lockKey, (System.currentTimeMillis() + milliseconds) + DELIMITER + uuid); final String[] oldValues = oldVal.split(Pattern.quote(DELIMITER)); if (Long.parseLong(oldValues[0]) + 1 <= System.currentTimeMillis()) { return true; } } return success; } /** * @see Redis Documentation: SET */ public void unlock(String lockKey, String value) { unlock(lockKey, value, 0, TimeUnit.MILLISECONDS); } /** * 延迟unlock * * @param lockKey key * @param uuid client(最好是唯一键的) * @param delayTime 延迟时间 * @param unit 时间单位 */ public void unlock(final String lockKey, final String uuid, long delayTime, TimeUnit unit) { if (StringUtils.isEmpty(lockKey)) { return; } if (delayTime <= 0) { doUnlock(lockKey, uuid); } else { EXECUTOR_SERVICE.schedule(() -> doUnlock(lockKey, uuid), delayTime, unit); } } /** * @param lockKey key * @param uuid client(最好是唯一键的) */ private void doUnlock(final String lockKey, final String uuid) { String val = stringRedisTemplate.opsForValue().get(lockKey); final String[] values = val.split(Pattern.quote(DELIMITER)); if (values.length <= 0) { return; } if (uuid.equals(values[1])) { stringRedisTemplate.delete(lockKey); } } }
结论
import com.google.common.cache.Cache;import com.google.common.cache.CacheBuilder;import lombok.extern.slf4j.Slf4j;import org.apache.commons.codec.digest.DigestUtils;import java.util.Objects;import java.util.concurrent.ConcurrentHashMap;import java.util.concurrent.ScheduledThreadPoolExecutor;import java.util.concurrent.ThreadPoolExecutor;import java.util.concurrent.TimeUnit;/** * @author lijing * 重复提交锁 */ @Slf4j public final classResubmitLock{privatestatic final ConcurrentHashMapLOCK_CACHE =newConcurrentHashMap<>(200);privatestatic final ScheduledThreadPoolExecutor EXECUTOR=newScheduledThreadPoolExecutor(5,newThreadPoolExecutor.DiscardPolicy());// private static final CacheCACHES = CacheBuilder.newBuilder()// 最大缓存 100 个// .maximumSize(1000)// 设置写缓存后 5 秒钟过期// .expireAfterWrite(5, TimeUnit.SECONDS)// .build();privateResubmitLock(){}/** * 静态内部类 单例模式 * * @return */privatestaticclassSingletonInstance{privatestatic final ResubmitLock INSTANCE=newResubmitLock();}publicstatic ResubmitLock getInstance(){return SingletonInstance.INSTANCE;}publicstatic String handleKey(String param){return DigestUtils.md5Hex(param ==null?"": param);}/** * 加锁 putIfAbsent 是原子操作保证线程安全 * * @param key 对应的key * @param value * @return */public boolean lock(final String key, Object value){return Objects.isNull(LOCK_CACHE.putIfAbsent(key, value));}/** * 延时释放锁 用以控制短时间内的重复提交 * * @param lock 是否需要解锁 * @param key 对应的key * @param delaySeconds 延时时间 */publicvoidunLock(final boolean lock, final String key, final int delaySeconds){if(lock){EXECUTOR.schedule(()->{LOCK_CACHE.remove(key);}, delaySeconds, TimeUnit.SECONDS);}}}
原文地址:https://www.cnblogs.com/coderjava/p/12992549.html
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