parsing dates with variable spaces

Question

I am using Joda to parse dates and have a format where leading zeros are not used, e.g.:

 Mon Nov 20 14:40:36 2006
 Mon Nov  6 14:40:36 2006

Note that the dayOfMonth field is left-padded with a blank.

Currently I seem to have to use two different formats and reparse if one fails

"EEE MMM dd HH:mm:ss yyyy"
"EEE MMM  d HH:mm:ss yyyy"

Is there a single format (or an API switch) which deals with both cases? (is the answer the same for SimpleDateFormat - which I don't use?)

Answer 1

java.time and format pattern letter p

Here’s the modern answer, using java.time, the successor of Joda-Time.

    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("EEE MMM ppd HH:mm:ss uuuu", Locale.ENGLISH);

    String[] stringsToParse = {
            "Mon Nov 20 14:40:36 2006",
            "Mon Nov  6 14:40:36 2006"
    };
    for (String dateTimeString : stringsToParse) {
        LocalDateTime dateTime = LocalDateTime.parse(dateTimeString, formatter);
        System.out.println(dateTime);
    }

Output:

2006-11-20T14:40:36
2006-11-06T14:40:36

To DateTimeFormatter.ofPattern format letter p means padding with spaces on the left. pp means padding to two position. It can be used for both formatting and — as here — parsing.

I know you asked about Joda-Time. The Joda-Time home page says:

Note that Joda-Time is considered to be a largely “finished” project. No major enhancements are planned. If using Java SE 8, please migrate to java.time (JSR-310).

Links

• Oracle tutorial: Date Time explaining how to use java.time.
• Documentation of DateTimeFormatter
• Joda-Time - Home

Answer 2

I have just created a quick program to check this -

SimpleDateFormat sdf = new SimpleDateFormat("EEE MMM d HH:mm:ss yyyy");

try {
    String source1 = "Mon Nov 20 14:40:36 2006";
    Date d1 = sdf.parse(source1);
    String source2 = "Mon Nov  6 14:40:36 2006";
    Date d2 = sdf.parse(source2);

    String res1 = sdf.format(d1);
    String res2 = sdf.format(d2);

    System.out.println(source1 +"="+ res1);
    System.out.println(source2 +"="+ res2);
} catch (ParseException e) {
    e.printStackTrace();
}

The output from this is -

Mon Nov 20 14:40:36 2006=Mon Nov 20 14:40:36 2006
Mon Nov  6 14:40:36 2006=Mon Nov 6 14:40:36 2006

So, even though source2 has the extra space, it is still parsed by

EEE MMM d HH:mm:ss yyyy

Hope that helps

Answer 3

I tried using a single 'd' as suggested above in logstash 1.1.1 but it still complained about a malformed date when a single digit day with an extra leading space was parsed. The following logstash rules did work.

timestamp => [ "MMM dd HH:mm:ss", "MMM  d HH:mm:ss" ]

It didn't matter which order the two date formats were in. No more warnings were output once I added both formats.