Jackson custom date formatter - json

Question

I want to serialize a Json object with a date field, into a Pojo.
For example
{
date: <some arbitrary date format>
}
to
#JsonFormat(???)
LocalDateTime dateTime;
The problem is that the date can be in any number of formats. For example, maybe just a year, just a date, or date and time. And even those can be in multiple formats.
2021
2021-5-23
2021/05/23
2021/05/23 02:07
2021-05-23 02:07:53
2021/05/23 02:07:50.567
I've already written a parser that has a list of formats and will loop through them until it finds one that works. How can I write a custom Jackson serializer or formatter that uses that code and can take a string from a Json object and properly convert it to a Date or LocalDateTime object in the Pojo?
If it makes a difference, I'm also doing this in SpringBoot

Answer 1

I think, you are talking about DEserializing? If so, you can create your own JsonDeserializer that supports LocalDateTime and register it with JsonComponent. This would look like this:
(The "input" can be accessed via p.getText())
#JsonComponent
public class LocalDateTimeDeserializer extends JsonDeserializer<LocalDateTime> {
#Override
public LocalDateTime deserialize(JsonParser p, DeserializationContext ctxt)
throws IOException, JsonProcessingException {
String stringValue = p.getText();
// Use your parser instead of this
DateTimeFormatter formatter = new DateTimeFormatterBuilder().appendPattern("yyyy[-MM-dd HH:mm:ss]")
.parseDefaulting(ChronoField.MONTH_OF_YEAR, 1)
.parseDefaulting(ChronoField.DAY_OF_MONTH, 1)
.parseDefaulting(ChronoField.HOUR_OF_DAY, 0)
.parseDefaulting(ChronoField.MINUTE_OF_HOUR, 0)
.parseDefaulting(ChronoField.SECOND_OF_MINUTE, 0).toFormatter();
return LocalDateTime.parse(stringValue, formatter);
}
}