程序猿的量化交易之路（18）--Cointrader之Event实体（6）

转载需注明：

事件，是Esper的重要概念。

这里我们定义个事件类。它是Temporal实体的派生类。

不过对Temporal简单的包装。其代码例如以下：

package org.cryptocoinpartners.schema;

import org.joda.time.Instant;

import javax.persistence.MappedSuperclass;

/**
 * Subclasses of Event may be posted to Context
 *
 * @author Tim Olson
 */

//是一个基类，在数据库中不创建表格。

@MappedSuperclass
public abstract class Event extends Temporal {

    /**
     * If the Event's time has not been set when it is being published, it will be set to the current time of the
     * publishing Context
     */
    public void publishedAt(Instant instant) {
        if( getTime() == null )
            setTime(instant);
    }

    /** Most events should use this constructor to provide the time of the original happening, not the time of
     *  object creation */
    protected Event(Instant time) {
        super(time);
    }

    protected Event() {}

}