从JDBC ResultSet中将日期作为字符串读取时指定的日期格式在哪里 [英] Where is the date format specified when reading a date as a string from JDBC ResultSet

问题描述

这与从ResultSet中读取日期作为字符串时的默认JDBC日期格式，但该问题实际上从未真正得到回答;人们只是提供了编写代码的替代方法。

This is exactly the same question as Default JDBC date format when reading date as a string from ResultSet, but that question was never actually answered as such; people just offered alternative ways to write the code.

我特别询问是否有人知道指定默认转换格式的位置，以及是否由JDBC规范定义在某个地方，或者只是留给单独的JDBC驱动程序。如果是后者，那么另外一个问题是Oracle 10g JDBC如何做到这一点？

I'm specifically asking if anyone knows where the default conversion format is specified, and if it is defined by a JDBC spec somewhere, or just left up to the individual JDBC driver. If the latter, then an additional question of how does Oracle 10g JDBC do this?

**已添加15-Jan：

** Added 15-Jan:

对不起，我认为问题很清楚，但显然不是。我不是要从数据库中检索日期值，也不需要有关于如何做到这一点的建议。

Sorry, I thought the question was sufficiently clear, but apparently not. I am not trying to retrieve a date value from a database, and have no need for suggestions on ways to do that.

我不认为这是重复的引用的问题，这就是为什么我在这里问了一个单独的问题。虽然标题几乎相同，但引用的问题（无论OP意图是什么）已经用从数据库中检索日期值的替代方法得到了回答，这不是我想知道的。

I do not think this is a duplicate of the referenced question, which is why I asked a separate question here. Whilst the title is the pretty much same, the referenced question (regardless of what the OP intended) has been answered with alternative approaches for retrieving a date value from a database, which is not what I wish to know.

干杯，

推荐答案

好的，所以跟踪JDBC代码，它看起来像Oracle驱动程序硬编码自己的格式：

Ok, so tracing through the JDBC code, it looks like the Oracle driver hard-codes its own formatting:

  int k = (((bytes[0 + j] & 255) - 100) * 100 + (bytes[1 + j] & 255)) - 100;
  String s = k + "-" + toStr(bytes[2 + j])
      + "-" + toStr(bytes[3 + j])
      + " " + toStr(bytes[4 + j] - 1)
      + ":" + toStr(bytes[5 + j] - 1)
      + ":" + toStr(bytes[6 + j] - 1)
      + ".0";

因此，我猜测：

1. 在任何JDBC规范中的任何地方都没有指定此行为。


2. 每个驱动程序库都可以返回它喜欢的任何格式。

我假设这些是因为不同的实现返回不同的格式。当然，仍然可能在JDBC规范中的某处强制使用此格式，并且某些实现不符合要求，但这似乎不太可能。我当然在JDBC规范中找不到任何引用（但这并不意味着它们不在某处！）。

I'm assuming these because different implementations return different formats. Of course, it is still possible that this format is mandated somewhere in a JDBC spec, and some implementations are non-conformant, but that seems unlikely. I certainly couldn't find any references to this in a JDBC spec (but that doesn't mean they are not there somewhere!).

然而，关键点是就我而言，格式是在库中进行硬编码，不能被任何环境或其他设置覆盖，但只要驱动程序库版本保持不变，也不会在系统中进行更改。

However, the key point as far as I am concerned, is that the format is hard-coded in the library and not overridable by any environment or other settings, but also won't change across systems as long as the driver library version remains the same.

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