Parse String for unknown TemporalAccessor

问题

I'm getting a request parameter with unknown temporal (date, time or timestamp in ISO format) and want to parse it into a java.time.temporal.TemporalAccessor:

• LocalDate when the string represents a date like "2018-02-28"
• or LocalDateTime when the string represents a timestamp like "2018-02-28T11:20:00"

The following attempt results into DateTimeParseException:

TemporalAccessor dt = DateTimeFormatter.ISO_DATE_TIME.parseBest(str, LocalDateTime::from, LocalDate::from);

Deciding on the length of the string or the occurrence of a "T", which DateTimeFormatter to use, seems to me a little bit hacky. As well as trying one format after another.

Any better solution?

回答1:

Your problem is that ISO_DATE_TIME expects a time, as the name indicates. In your case you need to use an optional section in your pattern.

This should work as required:

DateTimeFormatter FMT = new DateTimeFormatterBuilder()
        .append(DateTimeFormatter.ISO_LOCAL_DATE)
        .optionalStart() //HERE WE INDICATE THAT THE TIME IS OPTIONAL
        .appendLiteral('T')
        .append(DateTimeFormatter.ISO_LOCAL_TIME)
        .toFormatter();

String input = "2018-02-28";
TemporalAccessor dt = FMT.parseBest(input, LocalDateTime::from, LocalDate::from);        

来源：https://stackoverflow.com/questions/49026914/parse-string-for-unknown-temporalaccessor