Spring Data Mongo：如何仅保存日期，即不保存时间

Question

In one of the collections I have a field that need to be set to the current date, for example '2018-01-26'. It should not include any time in it. This makes it easy for me to query the documents based on a date. I have tried with the below code and it is always saving date with time in it.

 @DateTimeFormat(iso= DateTimeFormat.ISO.DATE_TIME)
private Date journeyDate;

or

 @DateTimeFormat(iso= DateTimeFormat.ISO.DATE)
    private Date journeyDate;

How can only save the date part in the database?

Answer 1

You cannot really set the date in Mongo as '2018-01-26'. Because whatever conversion we do, in the end we need to create a Date object to save in Mongo. And a date object cannot exists without time.

However what you can do is, you can control what is stored by writing a custom converter and registering it.
In this converter what I am doing is truncating all the date to start of the day, that means the time for all the dates is set to 00:00:00(irrespecitve of their time). This way you have same time for all days. I hope this would help in writing the query you need.

@Configuration
public class MongoConverterConfig
{

  @Bean
  public CustomConversions dateConversions()
  {
    List<Converter<?, ?>> converterList = new ArrayList<Converter<?, ?>>();
    converterList.add(new DateConverter());
    return new CustomConversions(converterList);
  }

  @WritingConverter
  static class DateConverter implements Converter<Date, Date> {

    @Override
    public Date convert(Date input) {
      if (input == null) {
        return null;
      }
      return Date.from(Instant.ofEpochMilli(input.getTime()).truncatedTo(ChronoUnit.DAYS));
    }
  }
}

If you really want to store just '2018-01-26' in mongo, then you will have to store it as a String, which I wouldn't recommend.