十、HikariCP源码分析之ConcurrentBag三

/**
 * 该方法将借出去的连接还回到连接池中
 * 不通过该方法还回的连接会造成内存泄露
 *
 * @param bagEntry the value to return to the bag
 * @throws NullPointerException  if value is null
 * @throws IllegalStateException if the requited value was not borrowed from the bag
 */
public void requite(final T bagEntry) {
   //⑧
   //lazySet方法不能保证连接会立刻被设置成未使用状态, 这是个延迟方法
   //这是一种优化, 如果要立即生效的话, 可能会需要使用volatile等, 让其他线程立即发现, 这会降低性能, 使用lazySet浪费不了多少时间, 但是不会浪费性能
   bagEntry.lazySet(STATE_NOT_IN_USE);

   //⑨
   //将连接放回到threadLocal中
   final List<Object> threadLocalList = threadList.get();
   if (threadLocalList != null) {
      threadLocalList.add(weakThreadLocals ? new WeakReference<>(bagEntry) : bagEntry);
   }
   //通知等待线程, 有可用连接
   synchronizer.signal();
}

public void add(final T bagEntry) {
   if (closed) {
      LOGGER.info("ConcurrentBag has been closed, ignoring add()");
      throw new IllegalStateException("ConcurrentBag has been closed, ignoring add()");
   }
   //⑩
   sharedList.add(bagEntry);
   synchronizer.signal();
}

public boolean remove(final T bagEntry) {
   //⑪
   //尝试标记移除使用中和保留状态的连接, 如果标记失败, 就是空闲的连接, 直接返回 false
   //也就是检查连接的状态, 不能移除空闲的连接或者已经标记移除的连接
   if (!bagEntry.compareAndSet(STATE_IN_USE, STATE_REMOVED) && !bagEntry.compareAndSet(STATE_RESERVED, STATE_REMOVED) && !closed) {
      LOGGER.warn("Attempt to remove an object from the bag that was not borrowed or reserved: {}", bagEntry);
      return false;
   }
   //如果上面标记成功了, 那么从连接池中移除这个连接
   final boolean removed = sharedList.remove(bagEntry);
   if (!removed && !closed) {
      LOGGER.warn("Attempt to remove an object from the bag that does not exist: {}", bagEntry);
   }

   // synchronizer.signal();
   return removed;
}