Custom Pattern for DateTimeFormat Doesn't Work

Question

I have a Rest Controller which has a request param:

@RequestParam(required = false) @DateTimeFormat(pattern = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'") ZonedDateTime startDate

When I Post data into my controller:

startDate=2020-12-02T18:07:33.251Z

However I get a 400 Bad Request error:

2020-12-02 18:20:32.428  WARN 26384 --- [nio-2000-exec-3] .w.s.m.s.DefaultHandlerExceptionResolver : Resolved [org.springframework.web.method.annotation.MethodArgumentTypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'java.time.ZonedDateTime'; nested exception is org.springframework.core.convert.ConversionFailedException: Failed to convert from type [java.lang.String] to type [@org.springframework.web.bind.annotation.RequestParam @org.springframework.format.annotation.DateTimeFormat java.time.ZonedDateTime] for value '2020-12-02T18:07:33.251Z'; nested exception is java.lang.IllegalArgumentException: Parse attempt failed for value [2020-12-02T18:07:33.251Z]]

Answer 1

Your date-time string, 2020-12-02T18:07:33.251Z is already in the default format used by ZonedDateTime#parse.

Demo:

import java.time.ZonedDateTime;

public class Main {
    public static void main(String args[]) {
        String strDateTime = "2020-12-02T18:07:33.251Z";
        ZonedDateTime zdt = ZonedDateTime.parse(strDateTime);
        System.out.println(zdt);
    }
}

Output:

2020-12-02T18:07:33.251Z

It means that you can specify the format, DateTimeFormatter.ISO_ZONED_DATE_TIME, which is the default format used by ZonedDateTime#parse. Change the annotation as

@RequestParam(required = false) @DateTimeFormat(pattern = DateTimeFormatter.ISO_ZONED_DATE_TIME) ZonedDateTime startDate

or

@RequestParam(required = false) @DateTimeFormat(iso = ISO.DATE_TIME) ZonedDateTime startDate

Check the Spring documentation page to learn more about the second option.

---

Some other important notes:

1. In any case, do not put a single quote around Z which stands for Zulu and represents date-time at UTC (which has a zone-offset of +00:00 hours); rather, use X for zone-offset.

Demo:

import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;

public class Main {
    public static void main(String args[]) {
        String strDateTime = "2020-12-02T18:07:33.251Z";
        ZonedDateTime zdt = ZonedDateTime.parse(strDateTime, DateTimeFormatter.ofPattern("yyyy-MM-dd'T'HH:mm:ss.SSSX"));
        System.out.println(zdt);
    }
}

Output:

2020-12-02T18:07:33.251Z

Check DateTimeFormatter to learn more about it.

2. This pattern is valid for SimpleDateFormat as well.

Demo:

import java.text.ParseException;
import java.text.SimpleDateFormat;

public class Main {
    public static void main(String args[]) throws ParseException {
        String strDateTime = "2020-12-02T18:07:33.251Z";
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss.SSSX");
        System.out.println(sdf.parse(strDateTime));
    }
}

However, the date-time API of java.util and their formatting API, SimpleDateFormat are outdated and error-prone. It is recommended to stop using them completely and switch to the modern date-time API.