package foundation.user;

import foundation.dao.preload.Bucket;
import foundation.data.entity.Entity;
import foundation.data.object.DataObject;

public class UserBucket extends Bucket<User> {

	private static UserBucket instance;
	
	static {
		instance = newInstance();
	}
	
	private UserBucket() {
		
	}
	
	public static UserBucket getInstance() {
		return instance;
	}
	
	public static UserBucket newInstance() {
		return new UserBucket();
	}

	@Override
	public void activate() {
		instance = this;
	}
	
	public User getOrLoad(String userId) {
		User result = null;
		
		try {
			result = get(userId);
			
			if (result == null) {
				synchronized (this) {
					result = get(userId);
					
					if (result == null) {
						//1. 如果用户不存在，从数据库中加载用户
						result = loadOneUserFromDB(userId);
						
						if (result == null) {
							return null;
						}
						
						//2. 将新加载的用户存放到Bucket中
						loadOne(result.getId(), result);
					}
				}
			}
		} 
		catch (Exception e) {
			e.printStackTrace();
		}
		
		return result;
	}

	private User loadOneUserFromDB(String userId) throws Exception {
		DataObject dataObject = DataObject.getInstance("sys_user");
		Entity entity = dataObject.getTableEntity(userId);
		
		if (entity == null) {
			return null;
		}
		
		User user = new User();
		user.load(entity);
		
		return user;
	}

}