如何使用Java处理日历TimeZones？ [英] How to handle calendar TimeZones using Java?

问题描述

我有一个Timestamp值来自我的应用程序。用户可以在任何给定的本地时区。

由于此日期用于WebService，假定时间总是在GMT，我需要转换用户的参数从（EST）到（GMT）。这里是踢球人：用户不知道他的TZ。他输入了他要发送给WS的创建日期，所以我需要的是：

用户输入： 5/1/2008 6:12 PM（EST）

WS的参数需要：5/1/2008 6:12 PM（GMT）

我知道时间戳默认情况下总是在GMT，但是当发送参数时，即使我从TS创建了我的日历（应该是在GMT），时间总是关闭除非用户在GMT。

  Timestamp issuedDate =（Timestamp）getACPValue（inputs_，issuedDate）; 
日历issueDate = convertTimestampToJavaCalendar（issuedDate）; 
 ... 
 private static java.util.Calendar convertTimestampToJavaCalendar（Timestamp ts_）{
 java.util.Calendar cal = java.util.Calendar.getInstance（
 GMT_TIMEZONE，EN_US_LOCALE ）; 
 cal.setTimeInMillis（ts_.getTime（））; 
 return cal; 
} 
  

使用前面的代码，这是我得到的结果为方便阅读）：

[2008年5月1日下午11:12]

解决方案

感谢大家的回应。经过进一步调查，我得到了正确的答案。正如Skip Head所提到的，TimeStamped我从我的应用程序得到的正在调整到用户的TimeZone。所以如果用户输入6:12 PM（EST），我会得到下午2:12（GMT）。我需要的是一种撤销转换的方法，以便用户输入的时间是我发送到WebServer请求的时间。这是我完成这个的方式：

  //获取用户的TimeZone 
 TimeZone currentTimeZone = sc_.getTimeZone 
 Calendar currentDt = new GregorianCalendar（currentTimeZone，EN_US_LOCALE）; 
 //从DST获取偏移量，将DST考虑在内
 int gmtOffset = currentTimeZone.getOffset（
 currentDt.get（Calendar.ERA），
 currentDt.get（Calendar.YEAR ），
 currentDt.get（Calendar.MONTH），
 currentDt.get（Calendar.DAY_OF_MONTH），
 currentDt.get（Calendar.DAY_OF_WEEK），
 currentDt.get 。毫秒））; 
 // convert to hours 
 gmtOffset = gmtOffset /（60 * 60 * 1000）; 
 System.out.println（Current User's TimeZone：+ currentTimeZone.getID（））; 
 System.out.println（GMT当前偏移量（小时）：+ gmtOffset）; 
 //从用户输入获取TS 
 Timestamp issuedDate =（Timestamp）getACPValue（inputs_，issuedDate）; 
 System.out.println（TS from ACP：+ issuedDate）; 
 //将TS设置为日历
日历issueDate = convertTimestampToJavaCalendar（issuedDate）; 
 //调整GMT（注意偏移否定）
 issueDate.add（Calendar.HOUR_OF_DAY，-gmtOffset）; 
 System.out.println（使用GMT和US_EN语言环境从TS转换的日历日期：
 + DateFormat.getDateTimeInstance（DateFormat.SHORT，DateFormat.SHORT）
 .format（issueDate.getTime （）））; 
  

代码的输出是:(用户输入5/1/2008 6:12 PM p>

当前用户时间区域：EST

GMT当前偏移量（小时）： - 4（通常为-5，除非调整DST）

来自ACP的TS：2008-05-01 14：12：00.0

使用GMT和US_EN从TS转换的日历日期区域设置：5/1/08 6:12 PM（GMT）

I have a Timestamp value that comes from my application. The user can be in any given local TimeZone.

Since this date is used for a WebService that assumes the time given is always in GMT, I have a need to convert the user's parameter from say (EST) to (GMT). Here's the kicker: The user is oblivious to his TZ. He enters the creation date that he wants to send to the WS, so what I need is:

User enters: 5/1/2008 6:12 PM (EST)
The parameter to the WS needs to be: 5/1/2008 6:12 PM (GMT)

I know TimeStamps are always supposed to be in GMT by default, but when sending the parameter, even though I created my Calendar from the TS (which is supposed to be in GMT), the hours are always off unless the user is in GMT. What am I missing?

Timestamp issuedDate = (Timestamp) getACPValue(inputs_, "issuedDate");
Calendar issueDate = convertTimestampToJavaCalendar(issuedDate);
...
private static java.util.Calendar convertTimestampToJavaCalendar(Timestamp ts_) {
  java.util.Calendar cal = java.util.Calendar.getInstance(
      GMT_TIMEZONE, EN_US_LOCALE);
  cal.setTimeInMillis(ts_.getTime());
  return cal;
}

With the previous Code, this is what I get as a result (Short Format for easy reading):

[May 1, 2008 11:12 PM]

解决方案

Thank you all for responding. After a further investigation I got to the right answer. As mentioned by Skip Head, the TimeStamped I was getting from my application was being adjusted to the user's TimeZone. So if the User entered 6:12 PM (EST) I would get 2:12 PM (GMT). What I needed was a way to undo the conversion so that the time entered by the user is the time I sent to the WebServer request. Here's how I accomplished this:

// Get TimeZone of user
TimeZone currentTimeZone = sc_.getTimeZone();
Calendar currentDt = new GregorianCalendar(currentTimeZone, EN_US_LOCALE);
// Get the Offset from GMT taking DST into account
int gmtOffset = currentTimeZone.getOffset(
    currentDt.get(Calendar.ERA), 
    currentDt.get(Calendar.YEAR), 
    currentDt.get(Calendar.MONTH), 
    currentDt.get(Calendar.DAY_OF_MONTH), 
    currentDt.get(Calendar.DAY_OF_WEEK), 
    currentDt.get(Calendar.MILLISECOND));
// convert to hours
gmtOffset = gmtOffset / (60*60*1000);
System.out.println("Current User's TimeZone: " + currentTimeZone.getID());
System.out.println("Current Offset from GMT (in hrs):" + gmtOffset);
// Get TS from User Input
Timestamp issuedDate = (Timestamp) getACPValue(inputs_, "issuedDate");
System.out.println("TS from ACP: " + issuedDate);
// Set TS into Calendar
Calendar issueDate = convertTimestampToJavaCalendar(issuedDate);
// Adjust for GMT (note the offset negation)
issueDate.add(Calendar.HOUR_OF_DAY, -gmtOffset);
System.out.println("Calendar Date converted from TS using GMT and US_EN Locale: "
    + DateFormat.getDateTimeInstance(DateFormat.SHORT, DateFormat.SHORT)
    .format(issueDate.getTime()));

The code's output is: (User entered 5/1/2008 6:12PM (EST)

Current User's TimeZone: EST
Current Offset from GMT (in hrs):-4 (Normally -5, except is DST adjusted)
TS from ACP: 2008-05-01 14:12:00.0
Calendar Date converted from TS using GMT and US_EN Locale: 5/1/08 6:12 PM (GMT)

这篇关于如何使用Java处理日历TimeZones？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！