AbstractRedisLockWithLua.java

package com.jarvis.cache.lock;

import java.io.UnsupportedEncodingException;
import java.util.ArrayList;
import java.util.List;

/**
 * 基于Redis+Lua实现分布式锁; 实现方法更容易理解，但性能相对会差些
 * @author jiayu.qiu
 */
public abstract class AbstractRedisLockWithLua implements ILock {

    /**
     * 分布式锁 KEY[1] lock key <br>
     * ARGV[1] 过期时间 ARGV[2] 缓存时长 返回值: 如果执行成功, 则返回1; 否则返回0
     */
    private static final String lockScriptStr="local lockKey= KEYS[1]\n"//
        + "local lock = redis.call('SETNX', lockKey, ARGV[1])\n" // 持锁
        + "if lock == 0 then\n" //
        + "  return 0\n" //
        + "end\n" //
        + "redis.call('EXPIRE', lockKey, tonumber(ARGV[2]))\n" // 持锁n秒
        + "return 1\n";

    private static byte[] lockScript;

    static {
        try {
            lockScript=lockScriptStr.getBytes("UTF-8");
        } catch(Exception e) {
            e.printStackTrace();
        }
    }

    protected abstract Long eval(byte[] lockScript, String key, List<byte[]> args) throws UnsupportedEncodingException;

    protected abstract void del(String key);

    @Override
    public boolean tryLock(String key, int lockExpire) {
        try {
            List<byte[]> args=new ArrayList<byte[]>();
            long expire2=System.currentTimeMillis() + (lockExpire * 1000);
            args.add(String.valueOf(expire2).getBytes("UTF-8"));
            args.add(String.valueOf(lockExpire).getBytes("UTF-8"));

            Long rv=eval(lockScript, key, args);
            return null != rv && rv.intValue() == 1;
        } catch(Exception e) {
            e.printStackTrace();
        }
        return false;
    }

    @Override
    public void unlock(String key) {
        try {
            del(key);
        } catch(Throwable e) {
        }
    }
}