??? 为什么需要分布式系统锁
??? 比如系统中的注册
??? 需要先判断用户账号是否被注册 没有被注册则保存用户注册信息数据
??? 在单系统情况下 可以这样做
??? String username = user.getUsername();
???? synchronized (username.intern()) {//防止多用户情况下 输入的相同账号都还未保存成功的情况下越过检查
??? ??? ??? if(userService.existUsername(username,"")){
??? ??? ??? ??? mav.addObject("usernameMessage","用户名已存在");
??? ??? ??? ??? return mav;
??? ??? ??? }
??? ??? ??? userService.save(user);
??? ??? }
???? 集群情况下可能是不同的服务器处理 无法阻止
?
??? 分布式事务锁 底层借助memcached实现
/**
?* 业务锁
?*
?* 通过 memcache 的 addCache获取锁
?*
?* @author 820381
?*
?*/
public class Lock {
??? /**
??? ?* 锁
??? ?* @param lockName
??? ?* @return??? true 成功/false 失败
??? ?*/
??? public static boolean lock(String lockName) {
??? ??? return getLock(lockName, 0);
??? }
???
??? /**
??? ?* 解除锁
??? ?* @param lockName
??? ?* @return
??? ?*/
??? public static boolean unlock(String lockName) {
??? ??? return CacheUtil.deleteKeyCache(lockName);
??? }
???
??? /**
??? ?* 锁，并在获得锁的时候执行回调，回调执行完成后，解除锁
??? ?* @param lockName??? 锁名
??? ?* @param call??? ??? 回调函数
??? ?* @return??? BusinessRuntimeException: ExceptionCode.CMN_LOCK_FAILED
??? ?* @throws BusinessException
??? ?*/
??? public static <T> T lock(String lockName, Callback<T> call) throws BusinessException {
??? ??? if(lock(lockName)) {
??? ??? ??? try {
??? ??? ??? ??? return call.handle();
??? ??? ??? } finally {
??? ??? ??? ??? unlock(lockName);
??? ??? ??? }
??? ??? } else {
??? ??? ??? throw new BusinessException(ExceptionCode.CMN_LOCK_FAILED,
??? ??? ??? ??? ??? MessageFormat.format("连接超时[{0}]", lockName));
??? ??? }
??? }
???
??? private static boolean getLock(String lockName, Integer count) {
??? ??? boolean gotLock = false;
??? ???
??? ??? if(count > 1000) {
??? ??? ??? return gotLock;
??? ??? }
??? ???
??? ??? while(true) {
??? ??? ??? gotLock = CacheUtil.addCache(lockName, true, null);
??? ??? ???
??? ??? ??? if(gotLock) {
??? ??? ??? ??? return gotLock;
??? ??? ??? } else {
??? ??? ??? ??? try {
??? ??? ??? ??? ??? Thread.sleep(200);
??? ??? ??? ??? } catch (InterruptedException e) {
??? ??? ??? ??? ??? // 不处理异常睡眠异常
??? ??? ??? ??? }
??? ??? ??? ???
??? ??? ??? ??? return getLock(lockName, ++count);
??? ??? ??? }
??? ??? }
??? }
}
?
?
/**
?*
?* @ClassName: CacheUtil
?* @Description: 缓存工具类
?* @author Fanhy
?* @date 2014-11-27 上午10:55:39
?*
?*/
public class CacheUtil {
??? /**
??? ?* 缓存客户端
??? ?*/
??? private static MemCachedClient memCachedClient;
??? /**
??? ?* 过期时间
??? ?*/
??? private String timeLenght;
??? /**
??? ?* 默认Key的超时时间(小于1000的值，除以1000以后都是0，即永不过期 )
??? ?*/
??? private static Date keyTimeOut;
??? @SuppressWarnings("unused")
??? private void init() {
??? ??? keyTimeOut = new Date(Integer.parseInt(timeLenght));// 24小时缓存
??? }
??? /**
??? ?*
??? ?* @MethodName: getKeyCache
??? ?* @Description: 获取缓存
??? ?* @param keyName
??? ?*??????????? 缓存键
??? ?* @return 返回数据
??? ?*/
??? public static Object getKeyCache(String keyName) {
??? ??? if (null != keyName) {
??? ??? ??? MemcachedItem item = memCachedClient.gets(keyName);
??? ??? ??? if (null != item) {
??? ??? ??? ??? return item.getValue();
??? ??? ??? }
??? ??? }
??? ??? return null;
??? }
??? /**
??? ?*
??? ?* @MethodName: setCache
??? ?* @Description: 设置缓存
??? ?* @param keyName
??? ?*??????????? 缓存主键
??? ?* @param value
??? ?*??????????? 缓存数据
??? ?* @param date
??? ?*??????????? 过期时间(new Date(60000)过期时间是60秒)(如不设置默认缓存24小时)(不得超过30天)
??? ?*/
??? public static void setCache(String keyName, Object value, Date date) {
??? ??? if (null != keyName && !"".equals(keyName)) {
??? ??? ??? if (null == date) {
??? ??? ??? ??? memCachedClient.set(keyName, value, keyTimeOut);
??? ??? ??? } else {
??? ??? ??? ??? memCachedClient.set(keyName, value, date);
??? ??? ??? }
??? ??? }
??? }
??? /**
??? ?*
??? ?* @MethodName: setCache
??? ?* @Description: 设置缓存
??? ?* @param keyName
??? ?*??????????? 缓存主键
??? ?* @param value
??? ?*??????????? 缓存数据
??? ?*/
??? public static void setCache(String keyName, Object value) {
??? ??? if (null != keyName && !"".equals(keyName)) {
??? ??? ??? memCachedClient.set(keyName, value, keyTimeOut);
??? ??? }
??? }
??? /**
??? ?*
??? ?* @MethodName: deleteKeyCache
??? ?* @Description: 删除缓存
??? ?* @param keyName
??? ?*??????????? key名称
??? ?*/
??? public static boolean deleteKeyCache(String keyName) {
??? ??? if (null != keyName && !"".equals(keyName)) {
??? ??? ??? return memCachedClient.delete(keyName);
??? ??? }
??? ??? return false;
??? }
??? public void setMemCachedClient(MemCachedClient memCachedClient) {
??? ??? CacheUtil.memCachedClient = memCachedClient;
??? }
??? public void setTimeLenght(String timeLenght) {
??? ??? this.timeLenght = timeLenght;
??? }
??? /**
??? ?*
??? ?* @MethodName: addCache
??? ?* @Description: 设置缓存不重复Key，暂时只用于分布式同步
??? ?* @param keyName
??? ?* @param value
??? ?* @param date
??? ?* @return void 返回类型
??? ?*/
??? public static boolean addCache(String keyName, Object value, Date date) {
??? ??? boolean isTrue = false;
??? ??? if (!StringUtils.isBlank(keyName)) {
??? ??? ??? if (null == date) {
??? ??? ??? ??? Date dt = new Date();
??? ??? ??? ??? date = DateUtils.addMinutes(dt, 3);
??? ??? ??? }
??? ??? ??? isTrue = memCachedClient.add(keyName, value, date);
??? ??? }
??? ??? return isTrue;
??? }
}
?
如何使用
@Aspect
@Component
public class LockAspect {
??? @Around("execution(* com.sfiec..*.*(..)) && @annotation(Lock)")
??? public Object around(final ProceedingJoinPoint point) throws Throwable {
??? ??? String lockName = getLockName(point);
??? ???
??? ??? return com.sfiec.oms.common.Lock.lock(lockName, new Callback<Object>() {
??? ??? ??? @Override
??? ??? ??? public Object handle() throws BusinessException {
??? ??? ??? ??? Object result;
??? ??? ??? ???
??? ??? ??? ??? try {
??? ??? ??? ??? ??? result = point.proceed();
??? ??? ??? ??? } catch (Throwable e) {
??? ??? ??? ??? ??? if(e instanceof BusinessException) {
??? ??? ??? ??? ??? ??? throw (BusinessException) e;
??? ??? ??? ??? ??? }
??? ??? ??? ??? ???
??? ??? ??? ??? ??? if(e instanceof BusinessRuntimeException) {
??? ??? ??? ??? ??? ??? throw (BusinessRuntimeException) e;
??? ??? ??? ??? ??? }
??? ??? ??? ??? ???
??? ??? ??? ??? ??? throw new BusinessException("", e);
??? ??? ??? ??? }
??? ??? ??? ???
??? ??? ??? ??? return result;
??? ??? ??? }
??? ??? });
??? }
???
??? private String getLockName(ProceedingJoinPoint point) {
??? ??? MethodSignature signature = MethodSignature.class.cast(point.getSignature());
??? ??? Lock lock = signature.getMethod().getAnnotation(Lock.class);
??? ??? // 不是自定义的锁标志的退出
??? ??? if(lock == null) {
??? ??? ??? return null;
??? ??? }
??? ???
??? ??? // 获取默认的锁
??? ??? String lockName = lock.value();
??? ???
??? ??? // 不存在占位符，则直接返回
??? ??? if(lockName.indexOf("${") == -1) {
??? ??? ??? return lockName;
??? ??? }
??? ???
??? ??? // 获取占位符的内容
??? ??? final Properties properties = new Properties();
??? ??? String[] parameterNames = signature.getParameterNames();
??? ??? Object[] args = point.getArgs();
??? ???
??? ??? for(int i = 0; i < parameterNames.length; i++) {
??? ??? ??? String name = parameterNames[i];
??? ??? ??? Object val = args[i];
??? ??? ???
??? ??? ??? if(isBaseDataType(val.getClass())) {
??? ??? ??? ??? val = String.valueOf(val);
??? ??? ??? }
??? ??? ???
??? ??? ??? properties.put(name, val);
??? ??? }
??? ???
??? ??? // TODO 如果存在 ${xx.xx} 属性，则使用反射获取内容
??? ???
??? ??? // 一般的 ${xxx}，直接获取内容
??? ??? PropertyPlaceholderHelper helper = new PropertyPlaceholderHelper("${", "}");
??? ??? String lockName2 = helper.replacePlaceholders(lockName, properties);
??? ??? return lockName2;
??? }
???
??? /**?
??? ? * 判断一个类是否为基本数据类型。?
??? ? * @param clazz 要判断的类。?
??? ? * @return true 表示为基本数据类型。?
??? ? */
??? @SuppressWarnings("rawtypes")
??? private static boolean isBaseDataType(Class clazz) {??
??? ???? return
??? ???? (
??? ???????? clazz.equals(String.class) ||??
??? ???????? clazz.equals(Integer.class)||??
??? ???????? clazz.equals(Byte.class) ||??
??? ???????? clazz.equals(Long.class) ||??
??? ???????? clazz.equals(Double.class) ||??
??? ???????? clazz.equals(Float.class) ||??
??? ???????? clazz.equals(Character.class) ||??
??? ???????? clazz.equals(Short.class) ||??
??? ???????? clazz.equals(BigDecimal.class) ||??
??? ???????? clazz.equals(BigInteger.class) ||??
??? ???????? clazz.equals(Boolean.class) ||??
??? ???????? clazz.equals(Date.class) ||??
??? ???????? clazz.isPrimitive()??
??? ???? );??
??? ?}
}
?
? @Lock(CommonConstant.LOCK_REGISTER + " ${user.username}")
??? public boolean register(User user) {
????????? if(userService.existUsername(username,"")){
??? ??? ??? ??? mav.addObject("usernameMessage","用户名已存在");
??? ??? ??? ??? return false;
??? ??? ??? }
??? ??? ??? userService.save(user);
????????? ? return true;
??? }
?
原文：http://wddpwzzhao123.iteye.com/blog/2211289