解析Java中的任何日期 [英] Parse any date in Java

问题描述

我知道这个问题是有问题的，显然你无法解析任何日期。但是，我发现python-dateutil库能够解析我抛出的每一个日期，同时在确定日期格式字符串的同时要求绝对零度。 Joda时间总是作为一个伟大的Java日期解析器出售，但是在选择格式（或创建自己的）之前，它仍然需要您决定您的日期格式。你不能只是调用DateFormatter.parse（mydate）并且神奇地得到一个Date对象。

I know this question is asked quite a bit, and obviously you can't parse any arbitrary date. However, I find that the python-dateutil library is able to parse every date I throw at it, all while requiring absolutely zero effort in figuring out a date format string. Joda time is always sold as being a great Java date parser, but it still requires you to decide what format your date is in before you pick a Format (or create your own). You can't just call DateFormatter.parse(mydate) and magically get a Date object back.

例如，日期Wed Mar 04 05:09:06 GMT -06：00 2009正确解析为python-dateutil：

For example, the date "Wed Mar 04 05:09:06 GMT-06:00 2009" is properly parsed with python-dateutil:

import dateutil.parser
print dateutil.parser.parse('Wed Mar 04 05:09:06 GMT-06:00 2009')

以下Joda时间通话不起作用：

but the following Joda time call doesn't work:

    String date = "Wed Mar 04 05:09:06 GMT-06:00 2009";
    DateTimeFormatter fmt = ISODateTimeFormat.dateTime();
    DateTime dt = fmt.parseDateTime(date);
    System.out.println(date);

创建您自己的DateTimeFormatter会破坏目的，因为这似乎和使用SimpleDateFormatter一样正确的格式字符串。

And creating your own DateTimeFormatter defeats the purpose, since that seems to be the same as using SimpleDateFormatter with the correct format string.

有没有可比较的方法来解析Java中的日期，像python-dateutil？我不关心错误，我只是希望它完美。

Is there a comparable way to parse a date in Java, like python-dateutil? I don't care about errors, I just want it to mostly perfect.

推荐答案

你最好的赌注是真正要求帮助正则表达式匹配日期格式模式和/或做强烈的强制。

Your best bet is really asking help to regex to match the date format pattern and/or to do brute forcing.

几年前，我写了一个有点傻的 DateUtil class 做了这项工作。以下是相关的摘录：

Several years ago I wrote a little silly DateUtil class which did the job. Here's an extract of relevance:

private static final Map<String, String> DATE_FORMAT_REGEXPS = new HashMap<String, String>() {{
    put("^\\d{8}$", "yyyyMMdd");
    put("^\\d{1,2}-\\d{1,2}-\\d{4}$", "dd-MM-yyyy");
    put("^\\d{4}-\\d{1,2}-\\d{1,2}$", "yyyy-MM-dd");
    put("^\\d{1,2}/\\d{1,2}/\\d{4}$", "MM/dd/yyyy");
    put("^\\d{4}/\\d{1,2}/\\d{1,2}$", "yyyy/MM/dd");
    put("^\\d{1,2}\\s[a-z]{3}\\s\\d{4}$", "dd MMM yyyy");
    put("^\\d{1,2}\\s[a-z]{4,}\\s\\d{4}$", "dd MMMM yyyy");
    put("^\\d{12}$", "yyyyMMddHHmm");
    put("^\\d{8}\\s\\d{4}$", "yyyyMMdd HHmm");
    put("^\\d{1,2}-\\d{1,2}-\\d{4}\\s\\d{1,2}:\\d{2}$", "dd-MM-yyyy HH:mm");
    put("^\\d{4}-\\d{1,2}-\\d{1,2}\\s\\d{1,2}:\\d{2}$", "yyyy-MM-dd HH:mm");
    put("^\\d{1,2}/\\d{1,2}/\\d{4}\\s\\d{1,2}:\\d{2}$", "MM/dd/yyyy HH:mm");
    put("^\\d{4}/\\d{1,2}/\\d{1,2}\\s\\d{1,2}:\\d{2}$", "yyyy/MM/dd HH:mm");
    put("^\\d{1,2}\\s[a-z]{3}\\s\\d{4}\\s\\d{1,2}:\\d{2}$", "dd MMM yyyy HH:mm");
    put("^\\d{1,2}\\s[a-z]{4,}\\s\\d{4}\\s\\d{1,2}:\\d{2}$", "dd MMMM yyyy HH:mm");
    put("^\\d{14}$", "yyyyMMddHHmmss");
    put("^\\d{8}\\s\\d{6}$", "yyyyMMdd HHmmss");
    put("^\\d{1,2}-\\d{1,2}-\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd-MM-yyyy HH:mm:ss");
    put("^\\d{4}-\\d{1,2}-\\d{1,2}\\s\\d{1,2}:\\d{2}:\\d{2}$", "yyyy-MM-dd HH:mm:ss");
    put("^\\d{1,2}/\\d{1,2}/\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "MM/dd/yyyy HH:mm:ss");
    put("^\\d{4}/\\d{1,2}/\\d{1,2}\\s\\d{1,2}:\\d{2}:\\d{2}$", "yyyy/MM/dd HH:mm:ss");
    put("^\\d{1,2}\\s[a-z]{3}\\s\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd MMM yyyy HH:mm:ss");
    put("^\\d{1,2}\\s[a-z]{4,}\\s\\d{4}\\s\\d{1,2}:\\d{2}:\\d{2}$", "dd MMMM yyyy HH:mm:ss");
}};

/**
 * Determine SimpleDateFormat pattern matching with the given date string. Returns null if
 * format is unknown. You can simply extend DateUtil with more formats if needed.
 * @param dateString The date string to determine the SimpleDateFormat pattern for.
 * @return The matching SimpleDateFormat pattern, or null if format is unknown.
 * @see SimpleDateFormat
 */
public static String determineDateFormat(String dateString) {
    for (String regexp : DATE_FORMAT_REGEXPS.keySet()) {
        if (dateString.toLowerCase().matches(regexp)) {
            return DATE_FORMAT_REGEXPS.get(regexp);
        }
    }
    return null; // Unknown format.
}

（咳嗽，双括号初始化，咳嗽，只是为了得到它适合100个char最大长度;））

(cough, double brace initialization, cough, it was just to get it all to fit in 100 char max length ;) )

您可以使用新的正则表达式和日期格式模式轻松扩展它。

You can easily expand it yourself with new regex and dateformat patterns.

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