Spring-boot: Default databinding for java 8 LocalDate

[anthofo]

Given an endpoint with a LocalDate parameter :

public void doSth(@RequestParam @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) LocalDate startDate) {
 ...
}

I must set @DateTimeFormat(iso = DateTimeFormat.ISO.DATE) everywhere I want to bind a LocalDate. This code is boilerplate so I defined a custom editor :

webDataBinder.registerCustomEditor(LocalDate.class, new LocalDateEditor());

But it would be great if spring boot was able to do this natively with a date format in the properties file, and ISO as default.

[philwebb]

DateTimeFormatterRegistrar has some options setters that we might be able to surface as properties.

[snekse]

What are the pros/cons of using WebDataBinder#registerCustomEditor vs FormatterRegistry#addConverter

[unlimitedsola]

+1, its painful to spam @DateTimeFormat everywhere

[ghost]

This should also work by default in POJOs for GET request. It does work for POST.

[xriva]

Vote up for this enhancement. Actually I feel somewhat surprised that there is no global configuration to change the default @DateTimeFormat.

[britter]

What are the pros/cons of using WebDataBinder#registerCustomEditor vs. FormatterRegistry#addConverter

I only tried the WebDataBinder approach. This had the problem, that Optional<LocalDate> did no longer work for parameters with @RequestParam(required = false). It works when using @DateTimeFormat.

[britter]

I found a way to make it work even with Optional<LocalDate>:

  @Bean
  public Formatter<LocalDate> localDateFormatter() {
    return new Formatter<LocalDate>() {
      @Override
      public LocalDate parse(String text, Locale locale) throws ParseException {
        return LocalDate.parse(text, DateTimeFormatter.ISO_DATE);
      }

      @Override
      public String print(LocalDate object, Locale locale) {
        return DateTimeFormatter.ISO_DATE.format(object);
      }
    };
  }

I tried to generalize this using the spring.mvc.date-pattern property and auto configuration in #9930.

[britter]

I've blogged about this: https://blog.codecentric.de/en/2017/08/parsing-of-localdate-query-parameters-in-spring-boot/

[jo-ka]

I just tried to use this new feature with Spring Boot 2.0.1 and ran into parsing problems that I described in this Stack Overflow answer. Is this intended behaviour, have I been doing something wrong? My expectation was that yyyy-MM-dd would work just fine.

[wilkinsona]

@jo-ka I think you've identified a bug. Can you please open a new issue? I believe the key difference is the use of ResolverStyle.STRICT when a custom format is specified. If no custom format is specified, the DataTimeFormatter is created using java.time.format.DateTimeFormatter.ofLocalizedDate(FormatStyle) which uses ResolverStyle.SMART. I suspect that inconsistency is accidental and, with confirmation from @bclozel, should be corrected.

[jo-ka]

@wilkinsona Okay, I'll open a new issue , but only after @bclozel confirmed this, right?

[wilkinsona]

Please open a new one now. If we have to close it because @bclozel disagrees with my analysis then that's better than it getting forgotten because it's only being tracked by this already-closed issue.