分布式锁（redis/mysql）

package com.fenqile.creditcard.appgatewaysale.provider.util;
import com.fenqile.redis.JedisProxy;
import java.util.Date;
/**
 * User: Rudy Tan
 * Date: 2017/11/20
 *
 * redis 相关操作
 */
public class RedisUtil {
    /**
     * 获取分布式锁
     *
     * @param key        string 缓存key
     * @param expireTime int 过期时间，单位秒
     * @return boolean true-抢到锁，false-没有抢到锁
     */
    public static boolean getDistributedLockSetTime(String key, Integer expireTime) {
        try {
            // 移除已经失效的锁
            String temp = JedisProxy.getMasterInstance().get(key);
            Long currentTime = (new Date()).getTime();
            if (null != temp && Long.valueOf(temp) < currentTime) {
                JedisProxy.getMasterInstance().del(key);
            }
            // 锁竞争
            Long nextTime = currentTime + Long.valueOf(expireTime) * 1000;
            Long result = JedisProxy.getMasterInstance().setnx(key, String.valueOf(nextTime));
            if (result == 1) {
                JedisProxy.getMasterInstance().expire(key, expireTime);
                return true;
            }
        } catch (Exception ignored) {
        }
        return false;
    }
}
复制代码

public boolean getLock(String key){
     select for update
     if (记录存在){
           update
     }else {
           insert 
   }
}
复制代码

-- 锁表，单库单表
CREATE TABLE IF NOT EXISTS credit_card_user_tag_db.t_tag_lock (
    -- 记录index
    Findex INT NOT NULL AUTO_INCREMENT COMMENT '自增索引id',
    -- 锁信息（key、计数器、过期时间、记录描述）
    Flock_name VARCHAR(128) DEFAULT '' NOT NULL COMMENT '锁名key值',
    Fcount INT NOT NULL DEFAULT 0 COMMENT '计数器',
    Fdeadline DATETIME NOT NULL DEFAULT '1970-01-01 00:00:00' COMMENT '锁过期时间',
    Fdesc VARCHAR(255) DEFAULT '' NOT NULL COMMENT '值/描述',
    
    -- 记录状态及相关事件
    Fcreate_time DATETIME NOT NULL DEFAULT '1970-01-01 00:00:00' COMMENT '创建时间',
    Fmodify_time DATETIME NOT NULL DEFAULT '1970-01-01 00:00:00' COMMENT '修改时间',
    Fstatus TINYINT NOT NULL DEFAULT 1 COMMENT '记录状态，0：无效，1：有效',
    -- 主键（PS：总索引数不能超过5）
    PRIMARY KEY (Findex),
    -- 唯一约束
    UNIQUE KEY uniq_Flock_name(Flock_name),
    -- 普通索引
    KEY idx_Fmodify_time(Fmodify_time)
)ENGINE=INNODB DEFAULT CHARSET=UTF8 COMMENT '信用卡|锁与计数器表|rudytan|20180412';
复制代码

// 开启事务
@Transactional
public boolean getLock(String key){
      // 获取中央锁
      select * from tbl where Flock_name="center_lock"    
    
     // 查询key相关记录
     select for update
     if (记录存在){
           update
     }else {
           insert 
   }
}
复制代码

/**
     * 初始化记录,如果有记录update,如果没有记录insert
     */
    private LockRecord initLockRecord(String key){
        // 查询记录是否存在
        LockRecord lockRecord = lockMapper.queryRecord(key);
        if (null == lockRecord) {
            // 记录不存在，创建
            lockRecord = new LockRecord();
            lockRecord.setLockName(key);
            lockRecord.setCount(0);
            lockRecord.setDesc("");
            lockRecord.setDeadline(new Date(0));
            lockRecord.setStatus(1);
            lockMapper.insertRecord(lockRecord);
        }
        return lockRecord;
    }
   /**
     * 获取锁，代码片段
     */
    @Override
    @Transactional
    public GetLockResponse getLock(GetLockRequest request) {
        // 检测参数
        if(StringUtils.isEmpty(request.lockName)) {
            ResultUtil.throwBusinessException(CreditCardErrorCode.PARAM_INVALID);
        }
        // 兼容参数初始化
        request.expireTime = null==request.expireTime? 31536000: request.expireTime;
        request.desc = Strings.isNullOrEmpty(request.desc)?"":request.desc;
        Long nowTime = new Date().getTime();
        GetLockResponse response = new GetLockResponse();
        response.lock = 0;
        // 获取中央锁，初始化记录
        lockMapper.queryRecordForUpdate("center_lock");
        LockRecord lockRecord = initLockRecord(request.lockName);
        // 未释放锁或未过期，获取失败
        if (lockRecord.getStatus() == 1
                && lockRecord.getDeadline().getTime() > nowTime){
            return response;
        }
        // 获取锁
        Date deadline = new Date(nowTime + request.expireTime*1000);
        int num = lockMapper.updateRecord(request.lockName, deadline, 0, request.desc, 1);
        response.lock = 1;
        return response;
    }
复制代码

// 开启事务
@Transactional
public boolean getLock(String key){
      // 获取中央锁
      select * from tbl where Flock_name="center_lock"    
    
     // 查询key相关记录
     select for update
     if (记录存在){
           update
     }else {
           insert 
   }
}
复制代码

/**
     * 获取中央锁Key
     */
    private boolean getCenterLock(String key){
        String prefix = "center_lock_";
        Long hash = SecurityUtil.crc32(key);
        if (null == hash){
            return false;
        }
        //取crc32中的最后两位值
        Integer len = hash.toString().length();
        String slot = hash.toString().substring(len-2);
        String centerLockKey = prefix + slot;
        lockMapper.queryRecordForUpdate(centerLockKey);
        return true;
    }
      /**
     * 获取锁
     */
    @Override
    @Transactional
    public GetLockResponse getLock(GetLockRequest request) {
        // 检测参数
        if(StringUtils.isEmpty(request.lockName)) {
            ResultUtil.throwBusinessException(CreditCardErrorCode.PARAM_INVALID);
        }
        // 兼容参数初始化
        request.expireTime = null==request.expireTime? 31536000: request.expireTime;
        request.desc = Strings.isNullOrEmpty(request.desc)?"":request.desc;
        Long nowTime = new Date().getTime();
        GetLockResponse response = new GetLockResponse();
        response.lock = 0;
        // 获取中央锁，初始化记录
        getCenterLock(request.lockName);
        LockRecord lockRecord = initLockRecord(request.lockName);
        // 未释放锁或未过期，获取失败
        if (lockRecord.getStatus() == 1
                && lockRecord.getDeadline().getTime() > nowTime){
            return response;
        }
        // 获取锁
        Date deadline = new Date(nowTime + request.expireTime*1000);
        int num = lockMapper.updateRecord(request.lockName, deadline, 0, request.desc, 1);
        response.lock = 1;
        return response;
    }
复制代码