Scala 转换 long 到 datetime

问题描述

我在项目中使用 nscala-time(Joda Time 的包装器)和 slick.我正在尝试使用此子句向数据库写入一行:

I am using nscala-time (wrapper for Joda Time) and slick for a project. I'm trying to use this clause to write a line to the database:

Article.insert(0,"title1", "hellothere", DateTime.now.getMillis.asInstanceOf[Timestamp])

显然 Slick 不支持 Joda Time 中定义的dateTime"类型，我必须使用 java.sql.Timestamp 代替.所以我决定在 insert 方法内部做一些转换，使用asInstanceOf".不幸的是，Scala 很快告诉我 Java.Long 不能转换为 Java.sql.Timestamp.然后我用了这个:

Apparently Slick does not support "dateTime" type defined in Joda Time, and I have to use java.sql.Timestamp instead. So I decide to do a little conversion inside the insert method, using "asInstanceOf". Unfortunately, Scala quickly tells me that Java.Long cannot be converted to Java.sql.Timestamp. Then I used this:

 val dateTime = new DateTime();
 val timeStamp = new Timestamp(dateTime.getMillis());

 Article.insert(0,"title1", "hellothere", timeStamp)

这很神奇，我只剩下困惑.

This magically works, and all I'm left with is confusion.

我怎样才能以一种方式而不是另一种方式转换它?我应该使用与 asInstanceOf 不同的转换吗?

How can I convert it one way but not the other? Should I use a different conversion than asInstanceOf?

推荐答案

你误解了 asInstanceOf 的作用:asInstanceOf 不转换任何东西.它所做的是对编译器撒谎，告诉它相信某事而不是使用它所拥有的知识.

You misunderstand what asInstanceOf does: asInstanceOf doesn't convert anything. What it does is lie to the compiler, telling it to believe something instead of going with the knowledge it has.

所以，你有一个Long，然后你得到一个Long，但假装它是一个Timestamp，这显然不是工作.

So, you had a Long, and then you got a Long, but pretended it was a Timestamp, which obviously doesn't work.

我有一个关于 asInstanceOf 的简单建议:永远不要使用它.

I have a simple recommendation regarding asInstanceOf: never use it.

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