是否有更好的方法将此时间戳格式化为ISO8601？

Question

I have a timestamp that looks like this: 2015-11-12T20:45:24+0000 . This is generated by someone else's script, which allegedly uses the UNIX date command (probably something along the lines of date -u +%Y-%m-%dT%H:%M:%S%z ).

However , according to Java's DateTimeFormatter , the closest ISO 8601 format for this would be ISO_OFFSET_DATE_TIME , which looks like: 2015-11-12T20:45:24+00:00 ( notice the extra colon at the end ). If I pass in my version of the timestamp, the parser is unable to process it, but if I manually add in the colon then there are no issues.

My question is, is there an easier, more reliable/robust way to handle these timestamps? I'm getting timestamps which may or may not have that final colon delimiting minutes and seconds, and currently my code has this validation in it:

// We expect a colon at index length-3 (the colon delimits the hours:minutes of the timezone offset)
char colon = ':';
int expectedIndexOfColon = string.length() - 3;

// If that colon is not there, add it
if (string.lastIndexOf(colon) == expectedIndexOfColon) {
    return string;
} else {
    int substringIndex = string.length() - 2;
    return string.substring(0, substringIndex) + colon + string.substring(substringIndex);
}

This looks hacky, and I was wondering if there was a more elegant way to handle these two different formats. I know about Joda-Time, but their parser also rejects the colon-less timestamp (from what I've tried). Additionally, Joda-Time recommends using Java's java.time for Java 8 anyways (which I am).

Answer 1

If your code is expecting multiple different formats, you need to accommodate for these difference.

A common approach is to put your expected formats into some kind of array of List and iterate over this, finding the format that doesn't throw an exception

For example:

• DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssZ") is able to parse 2015-11-12T20:45:24+0000
• DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssz") is able to parse 2015-11-12T20:45:24+00:00

You could use something like...

public static LocalDateTime parse(String text, List<DateTimeFormatter> formats) {
    LocalDateTime ldt = null;
    for (DateTimeFormatter formatter : formats) {
        try {
            ldt = LocalDateTime.parse(text, formatter);
        } catch (DateTimeParseException e) {
            // Maybe log the failure if you're interested
        }
    }
    return ldt;
}

Then you might use something like...

List<DateTimeFormatter> formats = new ArrayList<>(2);
formats.add(DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssZ"));
formats.add(DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ssz"));
System.out.println(parse("2015-11-12T20:45:24+0000", formats));
System.out.println(parse("2015-11-12T20:45:24+00:00", formats));

Which outputs...

2015-11-12T20:45:24
2015-11-12T20:45:24