protected <T> T getDetaul(T t, T defaultValue) throws Exception { if (defaultValue == null) { throw new Exception("默认值为空"); } if (t == null) { t = defaultValue; } return t; }
时间: 2024-02-14 16:30:46 浏览: 63
根据你提供的代码片段,这段代码是一个泛型方法 `getDetaul()` 的定义。
该方法接受两个参数 `t` 和 `defaultValue`,它们都是泛型类型 `T`。
首先,它检查 `defaultValue` 是否为 null。如果是 null,则抛出一个异常,提示默认值为空。
接下来,它检查 `t` 是否为 null。如果是 null,则将 `t` 的值赋为 `defaultValue`。
最后,返回 `t` 的值。
这个方法的目的是在给定的值 `t` 为 null 的情况下,返回一个默认值 `defaultValue`。如果 `defaultValue` 也为 null,则会抛出异常。
相关问题
@Slf4j @Aspect @Component public class DistributedLockAspect { private final ExpressionParser parser = new SpelExpressionParser(); private final DefaultParameterNameDiscoverer discoverer = new DefaultParameterNameDiscoverer(); @Autowired private RedissonClient redissonClient; @Around("@annotation(distributedLock)") public Object lock(ProceedingJoinPoint joinPoint, DistributedLock distributedLock) throws Throwable { // 使用spel解析注解中定义的key String keyValue = parseKeyValue(joinPoint, distributedLock.value()); // 拼接出锁名称 String lockName = connectLockName(distributedLock.keyPrefix(), keyValue, distributedLock.separator()); // 获取锁 RLock lock = getLock(distributedLock.lockModel(), lockName); try { if (lock.tryLock(distributedLock.waitLockMSec(), distributedLock.lockExpireMSec(), TimeUnit.MILLISECONDS)) { log.info("获取锁:{}", lockName); return joinPoint.proceed(); } throw new LockException(distributedLock.message()); } finally { lock.unlock(); } } private RLock getLock(DistributedLock.LockModel lockModel, String lockName) { switch (lockModel) { case FAIR: //公平锁 return redissonClient.getFairLock(lockName); case READ: //读之前加读锁,读锁的作用就是等待该lockkey释放写锁以后再读 return redissonClient.getReadWriteLock(lockName).readLock(); case WRITE: //写之前加写锁,写锁加锁成功,读锁只能等待 return redissonClient.getReadWriteLock(lockName).writeLock(); case REENTRANT: default: //可重入锁 return redissonClient.getLock(lockName); } } private String connectLockName(String prefix, String key, String separator) { if (StringUtils.isNotBlank(prefix)) { return prefix + separator + key; } return key; } private String parseKeyValue(ProceedingJoinPoint joinPoints, String elExpr) { MethodSignature methodSignature = (MethodSignature) joinPoints.getSignature(); Method method = methodSignature.getMethod(); //获取方法的参数值 Object[] args = joinPoints.getArgs(); EvaluationContext context = new StandardEvaluationContext(); String[] params = discoverer.getParameterNames(method); if (params != null) { for (int i = 0; i < params.length; i++) { context.setVariable(params[i], args[i]); } } //根据spel表达式获取值 Expression expression = parser.parseExpression(elExpr); Object value = expression.getValue(context); if (value != null) { return value.toString(); } return "defaultLockKey"; } }解释一下这段代码
这段代码是一个基于Spring AOP实现的分布式锁切面,它使用了Redisson作为分布式锁的实现。在使用@DistributedLock注解的方法上,会拦截方法的执行,获取注解中定义的key值,拼接出锁名称,然后获取对应的锁。如果获取锁成功,则执行方法,否则抛出LockException异常。其中,锁的类型可以是可重入锁、公平锁、读锁或写锁,可以通过注解中的lockModel属性指定。
throw new IllegalArgumentException("Cannot divide by zero.");
As an AI language model, I cannot divide by zero. If you are trying to implement this code, it means that you are trying to perform a division operation where the denominator is zero. This is not possible in mathematics, and therefore, the code throws an IllegalArgumentException with the message "Cannot divide by zero."
To avoid this error, you should add a check before performing the division operation to see if the denominator is zero. If it is, you can handle the error by throwing an exception or returning a default value.