:date:

If you are starting a Spring Boot project today, chances are that you want to use Java 8.

One of the most awesome features in Java 8 is the Date and Time API, also known as JSR-310.

By default, Jackson will treat the new dates as normal objects and serialize all the fields that they contain, which will probably not suit your needs.

I will show you how to fix the problem with the jackson-datatype-jsr310 library, within a Spring Boot project, but the concepts here are applicable to any application using Jackson.

The code is available on github if you want to take a look.

The problem

Let’s write a simple controller:

@RestController
public class DateController {

    @RequestMapping("/localDate")
    public LocalDate todayLocalDate() {
        return LocalDate.now();
    }

    @RequestMapping("/offsetDateTime")
    public OffsetDateTime todayOffsetDateTime() {
        return OffsetDateTime.now();
    }
}

Simple, right? What could possibly go wrong?

Well, it’s probably not what you expected. This output is not going to be easy to use in your client application.

More importantly, are you going to send this kind of format to your server when you are targeting a Java date?

The output of offsetDateTime is pretty similar in terms of unusualness.

The solution

Turns out that the solution is pretty straight-forward. Just add the following dependency to your project:

compile 'com.fasterxml.jackson.datatype:jackson-datatype-jsr310'

And the result, for LocalDateTime:

[
  2016,
  2,
  2
]

And for OffsetDateTime:

1454451664.708000000

Happy? No? Let’s try improve the solution.

Tweaking the output

If you look at how the library works internally, you will see that the output depends on some features being activated or not.

To have a better default, we can override the default ObjectMapper and give it a different config:

@Configuration
public class JacksonConfig {

    @Bean
    @Primary
    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
//        objectMapper.configure(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS, false);
        return objectMapper;
    }
}

This time the result is, for LocalDateTime:

2016-02-02

And for OffsetDateTime:

2016-02-02T23:24:08.255+01:00

If you uncomment the second line, dates will be written as timestamps without the nanoseconds but unfortunately, it is mutually exclusive with the first option.

Nevertheless, those formats are a lot more sensible and understandable by client libraries like momentjs.

Conclusion

It takes just a little configuration to make JSR-310 dates behave correctly with Jackson and Spring Boot.

As always, check out the project on github and tell if this helped!

Geoffroy Warin

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